Online First
Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes/issues, but are citable by Digital Object Identifier (DOI).
Display Method:
, Available online , doi: 10.11883/bzycj-2024-0225
Read OL
PDF 
Cited By
Abstract:
With its high design freedom and rapid prototyping capabilities, additive manufacturing (AM) offers significant advantages in manufacturing critical components with complex geometries for the aerospace and defense industries. Ti-6Al-4V alloy, leveraging its exceptional combination of low density, high specific strength, and creep resistance, are extensively employed in critical structures that are frequently subjected to impact loading in aerospace and defense systems. A thorough understanding of the mechanical properties and underlying mechanisms of the additively manufactured Ti-6Al-4V alloy under static and dynamic loading is crucial for enhancing the service performance of these components. This paper systematically reviews and summarizes the latest advancements in the mechanical response of AM Ti-6Al-4V titanium alloys. Firstly, a brief overview of the classification and working principles of typical metal additive manufacturing (AM) technologies is provided. Subsequently, research efforts on the quasi-static tensile and dynamic compressive properties of additively manufactured Ti-6Al-4V titanium alloy are systematically reviewed, followed by a comparative analysis of its mechanical performance against cast and forged Ti-6Al-4V components. Furthermore, the mechanisms of correlation between the microstructure and mechanical behaviors of typical metal additive manufactured titanium alloys. Additionally, the commonly used post-processing techniques to mitigate the anisotropic mechanical response of AM Ti-6Al-4V alloy under static loading are summarizes.
With its high design freedom and rapid prototyping capabilities, additive manufacturing (AM) offers significant advantages in manufacturing critical components with complex geometries for the aerospace and defense industries. Ti-6Al-4V alloy, leveraging its exceptional combination of low density, high specific strength, and creep resistance, are extensively employed in critical structures that are frequently subjected to impact loading in aerospace and defense systems. A thorough understanding of the mechanical properties and underlying mechanisms of the additively manufactured Ti-6Al-4V alloy under static and dynamic loading is crucial for enhancing the service performance of these components. This paper systematically reviews and summarizes the latest advancements in the mechanical response of AM Ti-6Al-4V titanium alloys. Firstly, a brief overview of the classification and working principles of typical metal additive manufacturing (AM) technologies is provided. Subsequently, research efforts on the quasi-static tensile and dynamic compressive properties of additively manufactured Ti-6Al-4V titanium alloy are systematically reviewed, followed by a comparative analysis of its mechanical performance against cast and forged Ti-6Al-4V components. Furthermore, the mechanisms of correlation between the microstructure and mechanical behaviors of typical metal additive manufactured titanium alloys. Additionally, the commonly used post-processing techniques to mitigate the anisotropic mechanical response of AM Ti-6Al-4V alloy under static loading are summarizes.
, Available online , doi: 10.11883/bzycj-2024-0119
Abstract:
H-section steel columns have been widely employed in industrial buildings and parking lots, etc., which are vulnerable to crane-loading or vehicle collisions. Based on above background and previous experimental studies, the lateral impact model and residual load-carrying capacity model are established by using Abaqus finite element software to analyze the performance of H-section steel columns during and after impact loading. Firstly, the working mechanism, including the deformation characteristics, stress evolution and energy dissipation, is analyzed. Results indicate that under impact loading, the deformation pattern is mainly dominated by the global deformation, with the local deformation of the upper flange and out-of-plane buckling of the web. The time history curve of impact force exhibits an obvious plateau phase, and the existence of the pre-axial compression clearly reduces the impact resistance of the specimens. In general, H-section steel columns present favorable ductility performance during impact loading. Subsequently, a total of 108 parametric models are constructed, and the effects of load parameters (impact mass, impact velocity and axial load ratio), material parameter (steel yield strength) and geometric parameters (sectional area and specimen length) on the impact force, deformation, and residual load-carrying capacity are emphatically studied. The results show that as the impact mass, impact velocity, and/or pre-axial loading ratio increase, both the global and local deformations of H-section steel column will increase, while the residual load-carrying capacity will decrease. Finally, by considering the multi-factor interactions, the formulas for predicting global deformation and local deformation during impact and the residual load-carrying performance after impact are proposed by using response surface method. Results show that pre-axial loading is a key factor affecting global deformation, while the impact velocity mainly affects local deformation. In addition, both the pre-axial loading and impact velocity significantly interact with other parameters. The proposed formulas can be employed for the damage evaluation and design of H-section steel columns during the whole impact process and after impact event.
H-section steel columns have been widely employed in industrial buildings and parking lots, etc., which are vulnerable to crane-loading or vehicle collisions. Based on above background and previous experimental studies, the lateral impact model and residual load-carrying capacity model are established by using Abaqus finite element software to analyze the performance of H-section steel columns during and after impact loading. Firstly, the working mechanism, including the deformation characteristics, stress evolution and energy dissipation, is analyzed. Results indicate that under impact loading, the deformation pattern is mainly dominated by the global deformation, with the local deformation of the upper flange and out-of-plane buckling of the web. The time history curve of impact force exhibits an obvious plateau phase, and the existence of the pre-axial compression clearly reduces the impact resistance of the specimens. In general, H-section steel columns present favorable ductility performance during impact loading. Subsequently, a total of 108 parametric models are constructed, and the effects of load parameters (impact mass, impact velocity and axial load ratio), material parameter (steel yield strength) and geometric parameters (sectional area and specimen length) on the impact force, deformation, and residual load-carrying capacity are emphatically studied. The results show that as the impact mass, impact velocity, and/or pre-axial loading ratio increase, both the global and local deformations of H-section steel column will increase, while the residual load-carrying capacity will decrease. Finally, by considering the multi-factor interactions, the formulas for predicting global deformation and local deformation during impact and the residual load-carrying performance after impact are proposed by using response surface method. Results show that pre-axial loading is a key factor affecting global deformation, while the impact velocity mainly affects local deformation. In addition, both the pre-axial loading and impact velocity significantly interact with other parameters. The proposed formulas can be employed for the damage evaluation and design of H-section steel columns during the whole impact process and after impact event.
, Available online , doi: 10.11883/bzycj-2024-0393
Abstract:
Traumatic brain injury (TBI) is the neurological disorder with the highest incidence and prevalence, and poses a huge public health burden for the whole society. An in-depth study of the biomechanics of TBI can help to improve the effectiveness of head protection, develop rapid assessment techniques and take timely interventions, thus reducing the risk of injury deterioration. As a numerical analysis tool, the finite element head model (FEHM) is able to simulate the dynamic response of the head during impact, including the spatial and temporal distribution of stress-strain in brain tissues, and the change of intracranial pressure, which provides an important basis for understanding the mechanical mechanism of traumatic brain injury (TBI). This paper summarizes in detail the current status and development of mainstream finite element models of the human head at home and abroad, traces the development of the models, summarises the characteristics of the models and introduces the research progress of TBI mechanisms based on finite element models. The summary and sorting out of related research will be helpful for the development of new FEHMs and provide theoretical guidance and technical support for the risk assessment of traumatic brain injury and the design of protective equipment.
Traumatic brain injury (TBI) is the neurological disorder with the highest incidence and prevalence, and poses a huge public health burden for the whole society. An in-depth study of the biomechanics of TBI can help to improve the effectiveness of head protection, develop rapid assessment techniques and take timely interventions, thus reducing the risk of injury deterioration. As a numerical analysis tool, the finite element head model (FEHM) is able to simulate the dynamic response of the head during impact, including the spatial and temporal distribution of stress-strain in brain tissues, and the change of intracranial pressure, which provides an important basis for understanding the mechanical mechanism of traumatic brain injury (TBI). This paper summarizes in detail the current status and development of mainstream finite element models of the human head at home and abroad, traces the development of the models, summarises the characteristics of the models and introduces the research progress of TBI mechanisms based on finite element models. The summary and sorting out of related research will be helpful for the development of new FEHMs and provide theoretical guidance and technical support for the risk assessment of traumatic brain injury and the design of protective equipment.
, Available online , doi: 10.11883/bzycj-2024-0002
Abstract:
To understand the dynamic fracture characteristics of nodular cast iron structures, such as the spent nuclear fuel storage and transportation vessel, under low temperature and dynamic loads, the mode Ⅰ dynamic fracture toughness (DFT) of nodular cast iron was experimentally investigated at different temperatures (20℃, −40℃, −60℃ and −80℃) using an improved split Hopkinson pressure bar technique. The ductile-brittle transition behavior of the material was specially investigated. The standard three-point bending specimens with fatigue crack were pre-fabricated before the experiment. A special fixture was used to replace the transmitter bar during the experiment, while the temperature was controlled by a specially designed environmental chamber. The crack initiation time of the specimens was determined by the strain gage method. The experimental-numerical method was used to determine the dynamic stress intensity factor (DSIF) at the crack tip. Mesh refinement and element transition was used at the crack tip region to ensure a high-accuracy result of displacement field. On this basis, the mode Ⅰ DFT of the material was finally determined. The results show that under the same impact velocity, the DFT and fracture initiation time of nodular cast iron decrease significantly with the decrease in temperature. The macroscopic fracture surface of nodular cast iron changes from rough to relatively flat with the decrease of temperature, which indicates the change in the failure modes of the material. The effect of temperature on the failure mode is further verified by the quantitative microscopic analysis of the fracture. As the temperature decreases, the number of dimples on the fracture surface decreases, while the river patterns as well as cleavage steps increase. It means that the ductility of the material is weakened but the brittleness is enhanced at low temperatures. This ductile-brittle transition phenomenon is consistent with the tendency of the measured toughness of the material.
To understand the dynamic fracture characteristics of nodular cast iron structures, such as the spent nuclear fuel storage and transportation vessel, under low temperature and dynamic loads, the mode Ⅰ dynamic fracture toughness (DFT) of nodular cast iron was experimentally investigated at different temperatures (20℃, −40℃, −60℃ and −80℃) using an improved split Hopkinson pressure bar technique. The ductile-brittle transition behavior of the material was specially investigated. The standard three-point bending specimens with fatigue crack were pre-fabricated before the experiment. A special fixture was used to replace the transmitter bar during the experiment, while the temperature was controlled by a specially designed environmental chamber. The crack initiation time of the specimens was determined by the strain gage method. The experimental-numerical method was used to determine the dynamic stress intensity factor (DSIF) at the crack tip. Mesh refinement and element transition was used at the crack tip region to ensure a high-accuracy result of displacement field. On this basis, the mode Ⅰ DFT of the material was finally determined. The results show that under the same impact velocity, the DFT and fracture initiation time of nodular cast iron decrease significantly with the decrease in temperature. The macroscopic fracture surface of nodular cast iron changes from rough to relatively flat with the decrease of temperature, which indicates the change in the failure modes of the material. The effect of temperature on the failure mode is further verified by the quantitative microscopic analysis of the fracture. As the temperature decreases, the number of dimples on the fracture surface decreases, while the river patterns as well as cleavage steps increase. It means that the ductility of the material is weakened but the brittleness is enhanced at low temperatures. This ductile-brittle transition phenomenon is consistent with the tendency of the measured toughness of the material.
, Available online , doi: 10.11883/bzycj-2024-0261
Abstract:
Tolerances in machining and assembly often result in gaps within engineering structures. Under strong dynamic loading, gap jets may form within these gaps, thereby posing a threat to the reliability and safety of the structure. However, the formation mechanism of gap jets differs from that of traditional high-speed metal jets, and its formation process still requires systematic study. Hypervelocity impact loading experiments on tungsten samples with gaps were conducted using a two-stage light gas gun, and the formation and evolution of the gap jet were recorded using a high-speed framing camera. A numerical model for predicting the formation of gap jets was established using ANSYS Autodyn, and the applicability of the numerical simulation method was validated by comparing the numerical results with the jet morphology and head velocity history data obtained from a representative experiment. The effects of flyer velocity, gap width, and gap half-angle on the formation of the gap jet were investigated by adjusting these parameters in the numerical model, and the variations in the gap jet head velocity and mass with respect to these factors were obtained. The limitations of the steady-state jet model were analyzed, and an empirical model was developed to predict the jet head velocity and mass based on the findings from numerical simulations. The results show that the numerical model based on the Eulerian method can accurately predict the formation of the gap jet under strong dynamic loading. Loading pressure is found to be the main factor controlling the jet head velocity and mass; as the loading pressure increases, both the jet head velocity and mass increase accordingly. The gap width and half-angle have little effect on the jet head velocity, but the mass increases linearly with the gap width and half-angle. Due to significant errors in estimating the gap closing velocity, the steady jet model fails to accurately predict the formation of the gap jet. In contrast, the developed empirical model shows good agreement with the numerical results.
Tolerances in machining and assembly often result in gaps within engineering structures. Under strong dynamic loading, gap jets may form within these gaps, thereby posing a threat to the reliability and safety of the structure. However, the formation mechanism of gap jets differs from that of traditional high-speed metal jets, and its formation process still requires systematic study. Hypervelocity impact loading experiments on tungsten samples with gaps were conducted using a two-stage light gas gun, and the formation and evolution of the gap jet were recorded using a high-speed framing camera. A numerical model for predicting the formation of gap jets was established using ANSYS Autodyn, and the applicability of the numerical simulation method was validated by comparing the numerical results with the jet morphology and head velocity history data obtained from a representative experiment. The effects of flyer velocity, gap width, and gap half-angle on the formation of the gap jet were investigated by adjusting these parameters in the numerical model, and the variations in the gap jet head velocity and mass with respect to these factors were obtained. The limitations of the steady-state jet model were analyzed, and an empirical model was developed to predict the jet head velocity and mass based on the findings from numerical simulations. The results show that the numerical model based on the Eulerian method can accurately predict the formation of the gap jet under strong dynamic loading. Loading pressure is found to be the main factor controlling the jet head velocity and mass; as the loading pressure increases, both the jet head velocity and mass increase accordingly. The gap width and half-angle have little effect on the jet head velocity, but the mass increases linearly with the gap width and half-angle. Due to significant errors in estimating the gap closing velocity, the steady jet model fails to accurately predict the formation of the gap jet. In contrast, the developed empirical model shows good agreement with the numerical results.
, Available online , doi: 10.11883/bzycj-2024-0181
Abstract:
To investigate the stress wave characteristics within concrete targets under hypervelocity impact, a stress wave testing system based on polyvinylidene difluoride (PVDF) piezoelectric stress gauges was established. A calibration method for PVDF piezoelectric stress gauges was proposed and conducted. The stress waveforms within concrete targets impacted by kilogram-scale cylindrical 93W tungsten alloy projectiles at hypervelocity were measured, and the generation and propagation mechanisms of stress waves were analyzed using numerical simulation methods. The following conclusions were drawn: (1) the dynamic characteristic parameters of the PVDF piezoelectric stress gauge were calibrated to yield a dynamic sensitivity coefficient of (17.5±0.5) pC/N for the PVDF piezoelectric stress gauge; (2) high signal-to-noise ratio stress waveforms within the concrete target under hypervelocity impact conditions were obtained using the PVDF piezoelectric stress gauge; (3) the stress waveforms obtained from numerical simulation were in good agreement with the experimentally measured waveforms where the maximum deviation of the stress wave peak values between simulation and experimental results is less than 20%, providing a useful tool for mechanism exploration; (4) the characteristics of stress waves within the concrete target and the mechanisms of generation and attenuation were further explored using numerical simulation methods.
To investigate the stress wave characteristics within concrete targets under hypervelocity impact, a stress wave testing system based on polyvinylidene difluoride (PVDF) piezoelectric stress gauges was established. A calibration method for PVDF piezoelectric stress gauges was proposed and conducted. The stress waveforms within concrete targets impacted by kilogram-scale cylindrical 93W tungsten alloy projectiles at hypervelocity were measured, and the generation and propagation mechanisms of stress waves were analyzed using numerical simulation methods. The following conclusions were drawn: (1) the dynamic characteristic parameters of the PVDF piezoelectric stress gauge were calibrated to yield a dynamic sensitivity coefficient of (17.5±0.5) pC/N for the PVDF piezoelectric stress gauge; (2) high signal-to-noise ratio stress waveforms within the concrete target under hypervelocity impact conditions were obtained using the PVDF piezoelectric stress gauge; (3) the stress waveforms obtained from numerical simulation were in good agreement with the experimentally measured waveforms where the maximum deviation of the stress wave peak values between simulation and experimental results is less than 20%, providing a useful tool for mechanism exploration; (4) the characteristics of stress waves within the concrete target and the mechanisms of generation and attenuation were further explored using numerical simulation methods.
, Available online , doi: 10.11883/bzycj-2024-0353
Abstract:
In practical engineering, rock frequently suffers from recurrent dynamic disturbances, posing serious threats to engineering safety. To investigate the dynamic mechanical behavior of jointed rock under cyclic dynamic disturbances, cyclic impact tests of single-jointed gabbro (SJG) were conducted using a split Hopkinson pressure bar (SHPB) test system. The stress equilibrium during the tests was verified using the three-wave method and the force balance coefficient method. The dynamic mechanical behavior of the specimens was comprehensively analyzed in terms of impact resistance, stress-strain relationships, energy and damage evolution, as well as dynamic failure mechanisms. The results show that single-jointed rock specimens can achieve stress equilibrium under cyclic impact conditions. The failure mode of the specimens under cyclic impacts is splitting, and the joint inclination angle significantly influences the impact resistance of the specimens. As the joint inclination angle increases, the impact resistance of the specimens also increases. During the cyclic impact process, strain rebound occurs in all specimens, and their mechanical properties do not monotonically degrade with an increasing number of impacts. The peak stress of the specimens generally exhibits a decreasing trend with the number of impacts. The cumulative damage coefficient, represented by dissipated energy, increases approximately linearly with the number of impacts, while the increase rate decreases with larger joint inclination angles. Under low-stress impact loading, the compressive-shear stress within single-jointed specimens is insufficient to generate shear cracks. The failure of specimens primarily results from the progressive propagation of tensile cracks induced by tensile stress, which eventually coalesce with the joint. The failure mechanism of multi-jointed rock masses resembles that of single-jointed rock masses. During cyclic impact loading, both compaction of micro-defects and initiation of micro-cracks at joints occur simultaneously. However, the impact resistance of multi-jointed specimens depends on whether the cracks can interconnect the joints. For intact rock specimens, the failure process initially involves compaction of micro-defects, followed by probabilistic activation of micro-cracks, ultimately leading to specimen failure.
In practical engineering, rock frequently suffers from recurrent dynamic disturbances, posing serious threats to engineering safety. To investigate the dynamic mechanical behavior of jointed rock under cyclic dynamic disturbances, cyclic impact tests of single-jointed gabbro (SJG) were conducted using a split Hopkinson pressure bar (SHPB) test system. The stress equilibrium during the tests was verified using the three-wave method and the force balance coefficient method. The dynamic mechanical behavior of the specimens was comprehensively analyzed in terms of impact resistance, stress-strain relationships, energy and damage evolution, as well as dynamic failure mechanisms. The results show that single-jointed rock specimens can achieve stress equilibrium under cyclic impact conditions. The failure mode of the specimens under cyclic impacts is splitting, and the joint inclination angle significantly influences the impact resistance of the specimens. As the joint inclination angle increases, the impact resistance of the specimens also increases. During the cyclic impact process, strain rebound occurs in all specimens, and their mechanical properties do not monotonically degrade with an increasing number of impacts. The peak stress of the specimens generally exhibits a decreasing trend with the number of impacts. The cumulative damage coefficient, represented by dissipated energy, increases approximately linearly with the number of impacts, while the increase rate decreases with larger joint inclination angles. Under low-stress impact loading, the compressive-shear stress within single-jointed specimens is insufficient to generate shear cracks. The failure of specimens primarily results from the progressive propagation of tensile cracks induced by tensile stress, which eventually coalesce with the joint. The failure mechanism of multi-jointed rock masses resembles that of single-jointed rock masses. During cyclic impact loading, both compaction of micro-defects and initiation of micro-cracks at joints occur simultaneously. However, the impact resistance of multi-jointed specimens depends on whether the cracks can interconnect the joints. For intact rock specimens, the failure process initially involves compaction of micro-defects, followed by probabilistic activation of micro-cracks, ultimately leading to specimen failure.
, Available online , doi: 10.11883/bzycj-2024-0177
Abstract:
High-strength steel has excellent mechanical properties, which has been utilized in the fields of explosion and impact. In order to study the blast resistance of high-strength steel plates, ANSYS/LS-DYNA software was first used to simulate the impact test on high-strength steel materials. By comparing with experimental results, the Johnson-Cook model parameters characterizing the dynamic constitutive behavior of high-strength steel are determined. Based on the above model parameters, the explosion simulation of high-strength steel plates under near-field explosions is further carried out. The interaction process between the explosion shock wave and the steel plate is systematically analyzed, and the size effects of the steel plate on its deformation characteristics and failure mode are explained. The results show that the Johnson-Cook model can effectively simulate the mechanical behavior of S690 high-strength steel at high strain rates. High-strength steel plates have a weakening effect on the propagation of shock waves. With the increase of steel plate thickness, the propagation range of shock wave through steel plate decreases gradually. For high-strength steel plates of different geometric dimensions, near-field explosions will cause three damage modes: petal-shaped fracture, small fracture and large deformation. It is found that the thickness is the decisive factor to determine the failure mode of steel plates under near-field explosions. For high-strength steel plates with large deformation, the increase of thickness and decrease of width will improve the ability of resistance to near-field explosions. In addition, there is a positive correlation between the ability of shock resistance of the high-strength steel plate and the width-thickness ratio. When the proportional distance is 0.13, a model can be provided to predict the maximum displacement range of the high-strength steel plate according to the steel plate size. The above conclusions can provide some guiding significance for the optimal design and engineering application of high-strength steel structures.
High-strength steel has excellent mechanical properties, which has been utilized in the fields of explosion and impact. In order to study the blast resistance of high-strength steel plates, ANSYS/LS-DYNA software was first used to simulate the impact test on high-strength steel materials. By comparing with experimental results, the Johnson-Cook model parameters characterizing the dynamic constitutive behavior of high-strength steel are determined. Based on the above model parameters, the explosion simulation of high-strength steel plates under near-field explosions is further carried out. The interaction process between the explosion shock wave and the steel plate is systematically analyzed, and the size effects of the steel plate on its deformation characteristics and failure mode are explained. The results show that the Johnson-Cook model can effectively simulate the mechanical behavior of S690 high-strength steel at high strain rates. High-strength steel plates have a weakening effect on the propagation of shock waves. With the increase of steel plate thickness, the propagation range of shock wave through steel plate decreases gradually. For high-strength steel plates of different geometric dimensions, near-field explosions will cause three damage modes: petal-shaped fracture, small fracture and large deformation. It is found that the thickness is the decisive factor to determine the failure mode of steel plates under near-field explosions. For high-strength steel plates with large deformation, the increase of thickness and decrease of width will improve the ability of resistance to near-field explosions. In addition, there is a positive correlation between the ability of shock resistance of the high-strength steel plate and the width-thickness ratio. When the proportional distance is 0.13, a model can be provided to predict the maximum displacement range of the high-strength steel plate according to the steel plate size. The above conclusions can provide some guiding significance for the optimal design and engineering application of high-strength steel structures.
, Available online , doi: 10.11883/bzycj-2024-0315
Abstract:
Structural damages in solid propellants can lead to combustion anomalies and affect ballistic performance. Utilizing synchrotron radiation X-ray computed tomography technology and an in-situ mechanical loading test system, the macro-meso structures of nitrate ester plasticized polyether (NEPE) solid propellant were observed in-situ at compressive rates of 0.1, 1.0, and 5.0 mm/s. The compressive process employed an intermittent loading mode. With loading paused each time the preset displacement was reached to enable scanning imaging, thereby capturing the state of the propellant at specific phases during compression. Following the in-situ imaging experiment, the tomographic images of the samples were processed through projection correction and phase recovery using PITRE and PITRE_BM software, followed by image bit-depth conversion to obtain 8-bit 2D grayscale slices. Through 3D reconstruction, the typical damages and evolutionary behaviors of the solid propellant were analyzed, exploring the macroscopic deformation as well as the distribution and propagation patterns of internal micro-cracks. Results indicate that most micro-cracks nucleate and grow at the interface between filled particles and the matrix, with meso-pore evolution being rate-dependent. Unlike the continuous damage growth under tensile loading, the nucleation, growth, and closure of pores occur simultaneously during compression. Under high-rate uniaxial compressive loading, the solid propellant exhibits characteristic trumpet-shaped deformation, with spatially distributed cracks primarily located around the propellant. Macroscopic surface damage results from micro-crack propagation between near-surface particles and the matrix, with crack propagation related to the spatial location of filled particles. Transversal and axial crack propagation modes exist under dynamic compressive loading, with the transition from vertically to horizontally oriented cracks in the matrix leading to crack closure.
Structural damages in solid propellants can lead to combustion anomalies and affect ballistic performance. Utilizing synchrotron radiation X-ray computed tomography technology and an in-situ mechanical loading test system, the macro-meso structures of nitrate ester plasticized polyether (NEPE) solid propellant were observed in-situ at compressive rates of 0.1, 1.0, and 5.0 mm/s. The compressive process employed an intermittent loading mode. With loading paused each time the preset displacement was reached to enable scanning imaging, thereby capturing the state of the propellant at specific phases during compression. Following the in-situ imaging experiment, the tomographic images of the samples were processed through projection correction and phase recovery using PITRE and PITRE_BM software, followed by image bit-depth conversion to obtain 8-bit 2D grayscale slices. Through 3D reconstruction, the typical damages and evolutionary behaviors of the solid propellant were analyzed, exploring the macroscopic deformation as well as the distribution and propagation patterns of internal micro-cracks. Results indicate that most micro-cracks nucleate and grow at the interface between filled particles and the matrix, with meso-pore evolution being rate-dependent. Unlike the continuous damage growth under tensile loading, the nucleation, growth, and closure of pores occur simultaneously during compression. Under high-rate uniaxial compressive loading, the solid propellant exhibits characteristic trumpet-shaped deformation, with spatially distributed cracks primarily located around the propellant. Macroscopic surface damage results from micro-crack propagation between near-surface particles and the matrix, with crack propagation related to the spatial location of filled particles. Transversal and axial crack propagation modes exist under dynamic compressive loading, with the transition from vertically to horizontally oriented cracks in the matrix leading to crack closure.
, Available online , doi: 10.11883/bzycj-2024-0147
Abstract:
In order to improve the quantitative characterization of the penetration process of tungsten alloy projectile into the target, the numerical methods such as FEM (finite element method), SPG (smoothed particle Galerkin), SPH (smoothed particle hydrodynamics), and FE-SPH (finite element-smoothed particle hydrodynamics) adaptive simulation methods were employed to simulate the penetration of tungsten alloy projectiles into Q235A steel targets. Based on numerical simulations, a comparison was made of the advantages and disadvantages of the four numerical simulation methods for calculating the residual velocity of the projectile after penetrating the target, the perforation diameter of the target, and the distribution of secondary fragments by the projectile penetration. The results show that, for calculating the residual velocity of the projectile, FEM and FE-SPH adaptive methods strictly rely on the selection of failure criteria and corresponding parameters, as FEM employs an element erosion algorithm to model material failure, while SPG method, as it does not require adjusting the failure parameters in bond failure mode, can obtain relatively accurate calculations; for predicting perforation diameter, FEM and FE-SPH adaptive methods accurately represent material boundaries and perforation morphology, although the perforation diameter varies significantly under different failure criteria, while the SPG method can accurately predict the perforation diameter of target plates due to its insensitive to failure parameters; for analzing secondary fragments generation and distribution, both FE-SPH adaptive and SPH methods effectively characterize these phenomena, while the FE-SPH adaptive method provides detailed information on large fragments, it is less computationally efficient than the SPH method.
In order to improve the quantitative characterization of the penetration process of tungsten alloy projectile into the target, the numerical methods such as FEM (finite element method), SPG (smoothed particle Galerkin), SPH (smoothed particle hydrodynamics), and FE-SPH (finite element-smoothed particle hydrodynamics) adaptive simulation methods were employed to simulate the penetration of tungsten alloy projectiles into Q235A steel targets. Based on numerical simulations, a comparison was made of the advantages and disadvantages of the four numerical simulation methods for calculating the residual velocity of the projectile after penetrating the target, the perforation diameter of the target, and the distribution of secondary fragments by the projectile penetration. The results show that, for calculating the residual velocity of the projectile, FEM and FE-SPH adaptive methods strictly rely on the selection of failure criteria and corresponding parameters, as FEM employs an element erosion algorithm to model material failure, while SPG method, as it does not require adjusting the failure parameters in bond failure mode, can obtain relatively accurate calculations; for predicting perforation diameter, FEM and FE-SPH adaptive methods accurately represent material boundaries and perforation morphology, although the perforation diameter varies significantly under different failure criteria, while the SPG method can accurately predict the perforation diameter of target plates due to its insensitive to failure parameters; for analzing secondary fragments generation and distribution, both FE-SPH adaptive and SPH methods effectively characterize these phenomena, while the FE-SPH adaptive method provides detailed information on large fragments, it is less computationally efficient than the SPH method.
, Available online , doi: 10.11883/bzycj-2024-0453
Abstract:
With the deterioration of the natural climate, hail impact has become a threat that cannot be ignored by civil aircraft. To study the hail impact damage characteristics of high-performance carbon fiber composites used for civil aircraft, we first investigated the impact force characteristics of ice spheres under high-speed impact through experiments, and the impact time history curves of ice spheres under different speeds were obtained using an air cannon test system. At the same time, to make the speed range of the ice sphere more extensive, some existing experiment data are introduced as a comparison to obtain the linear growth relationship between the peak impact force and the kinetic energy of the ice sphere. Subsequently, a single ice sphere impact test was conducted on the T800/3200 carbon fiber composite laminates. It was found that the concave of the front core damage area forms a 45° angle with the boundary of the target plate, which is related to the carbon fiber layup mode, and the damage degree depends on the initial speed of the ice sphere. To further quantify the relationship between the damage degree of the laminate and the kinetic energy of the ice sphere, ultrasonic C-scanning was used to obtain the damaged area of the target plate, and the damage percentage was extracted by software analysis. The results show that the percentage of internal interlayer delamination increases linearly with the kinetic energy of the ice sphere. After that, repeated impact tests of ice spheres were carried out on the target plate with the same thickness, and as expected, the macro damage degree increased with the number of impacts. Finally, the front and back surfaces of the composite laminates were completely delaminated, resulting in a large number of fibers being pulled out and displaying a penetrating through-thickness damage pattern. The deflection of the center point of the target plate was selected as the quantitative damage index, and according to the data analysis of the measured results, it was found that there is a quadratic relationship between the deflection of the center point of the carbon fiber plate and the accumulated kinetic energy of the ice sphere. The apex of the parabola can well reflect the accumulated kinetic energy required for the target plate penetration.
With the deterioration of the natural climate, hail impact has become a threat that cannot be ignored by civil aircraft. To study the hail impact damage characteristics of high-performance carbon fiber composites used for civil aircraft, we first investigated the impact force characteristics of ice spheres under high-speed impact through experiments, and the impact time history curves of ice spheres under different speeds were obtained using an air cannon test system. At the same time, to make the speed range of the ice sphere more extensive, some existing experiment data are introduced as a comparison to obtain the linear growth relationship between the peak impact force and the kinetic energy of the ice sphere. Subsequently, a single ice sphere impact test was conducted on the T800/3200 carbon fiber composite laminates. It was found that the concave of the front core damage area forms a 45° angle with the boundary of the target plate, which is related to the carbon fiber layup mode, and the damage degree depends on the initial speed of the ice sphere. To further quantify the relationship between the damage degree of the laminate and the kinetic energy of the ice sphere, ultrasonic C-scanning was used to obtain the damaged area of the target plate, and the damage percentage was extracted by software analysis. The results show that the percentage of internal interlayer delamination increases linearly with the kinetic energy of the ice sphere. After that, repeated impact tests of ice spheres were carried out on the target plate with the same thickness, and as expected, the macro damage degree increased with the number of impacts. Finally, the front and back surfaces of the composite laminates were completely delaminated, resulting in a large number of fibers being pulled out and displaying a penetrating through-thickness damage pattern. The deflection of the center point of the target plate was selected as the quantitative damage index, and according to the data analysis of the measured results, it was found that there is a quadratic relationship between the deflection of the center point of the carbon fiber plate and the accumulated kinetic energy of the ice sphere. The apex of the parabola can well reflect the accumulated kinetic energy required for the target plate penetration.
, Available online , doi: 10.11883/bzycj-2024-0278
Abstract:
In order to investigate the damage mechanisms of zirconium-based amorphous alloy fragments penetrating carbon fiber targets and their subsequent effects on target failure, ballistic experiments were conducted using a 12.7 mm ballistic gun. The experiments involved spherical zirconium-based amorphous alloy fragments impacting a composite target system consisting of a 6-mm thick carbon fiber laminate and a 2-mm thick LY12 alloy plate. These targets were arranged in both stacked and spaced configurations to evaluate the effects of target configuration on the damage caused by fragment impact. To quantitatively assess the subsequent damage, image recognition technology was employed to analyze the damage area of the LY12 target after impact.The results indicated that the damage area of the carbon fiber target was positively correlated with the velocity of the impacting fragment, with no significant hole expansion observed. On the front side, damage primarily resulted from fiber shear failure and compressive deformation, while the back face of the carbon fiber laminate exhibited tensile tearing and interlaminar delamination. These findings suggest that the carbon fiber target experienced a combination of mechanical damage modes, including shear and compressive deformation on the impact side, and tensile and delamination failures on the rear face, as a result of the high-velocity impact.In the case of the LY12 aluminum alloy target, the damage area increased with fragment velocity. When the velocity was below 954.7 m/s, the damage area on the LY12 target in the spaced configuration was smaller than that of the stacked configuration. However, as the fragment velocity increased, the damage area of the LY12 target in the spaced configuration grew rapidly, while the damage area in the stacked configuration increased more gradually. At higher velocities, the damage area in the spaced configuration was significantly larger than that in the stacked configuration. This trend suggests that for high-velocity impacts, the spaced configuration of the targets was more effective in promoting greater damage to the LY12 target.
In order to investigate the damage mechanisms of zirconium-based amorphous alloy fragments penetrating carbon fiber targets and their subsequent effects on target failure, ballistic experiments were conducted using a 12.7 mm ballistic gun. The experiments involved spherical zirconium-based amorphous alloy fragments impacting a composite target system consisting of a 6-mm thick carbon fiber laminate and a 2-mm thick LY12 alloy plate. These targets were arranged in both stacked and spaced configurations to evaluate the effects of target configuration on the damage caused by fragment impact. To quantitatively assess the subsequent damage, image recognition technology was employed to analyze the damage area of the LY12 target after impact.The results indicated that the damage area of the carbon fiber target was positively correlated with the velocity of the impacting fragment, with no significant hole expansion observed. On the front side, damage primarily resulted from fiber shear failure and compressive deformation, while the back face of the carbon fiber laminate exhibited tensile tearing and interlaminar delamination. These findings suggest that the carbon fiber target experienced a combination of mechanical damage modes, including shear and compressive deformation on the impact side, and tensile and delamination failures on the rear face, as a result of the high-velocity impact.In the case of the LY12 aluminum alloy target, the damage area increased with fragment velocity. When the velocity was below 954.7 m/s, the damage area on the LY12 target in the spaced configuration was smaller than that of the stacked configuration. However, as the fragment velocity increased, the damage area of the LY12 target in the spaced configuration grew rapidly, while the damage area in the stacked configuration increased more gradually. At higher velocities, the damage area in the spaced configuration was significantly larger than that in the stacked configuration. This trend suggests that for high-velocity impacts, the spaced configuration of the targets was more effective in promoting greater damage to the LY12 target.
, Available online , doi: 10.11883/bzycj-2024-0335
Abstract:
In order to take into account the influence of the crack roughness, first of all, on basis of the calculation model for the rockmass macroscopic damage variable which can take into account the crack geometry parameter, strength parameter and deformation parameter, a calculation model for the rockmass macroscopic damage variable is proposed by introducing the JRC-JCS shear strength model for the rough crack established by Barton, which can consider the crack roughness. Secondly, the proposed calculation model is introduced into the uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack, which both considers the coupling of the macroscopic and microscopic defects, and then a uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack is established which can consider the crack roughness at the same time. Finally, the effect of crack roughness JRC and crack basic friction angle φb and crack length 2a on rockmass dynamic mechanical property is studied with the parametric sensitivity analysis. The result shows that the rockmass dynamic climax strength increases from 26.42 MPa to 27.28 and 28.37 MPa with JRC increasing from 0 to 10 and 20 respectively. The rockmass dynamic climax strength increases from 26.42 MPa to 27.28 and 28.80 MPa with φb increasing from 0° to 15° and 30° respectively. The rockmass dynamic climax strength decreases from 31.37 MPa to 27.28 and 23.90 MPa with 2a increasing from 1cm to 2 and 3cm respectively. At the same time, in order to describe the influence of the crack roughness more accurately, the crack fractal dimension is introduced into the dynamic damage model for the rock mass, which not only improves the calculation accuracy of the model, but also broadens its application range, which is more convenient for practical engineering application.
In order to take into account the influence of the crack roughness, first of all, on basis of the calculation model for the rockmass macroscopic damage variable which can take into account the crack geometry parameter, strength parameter and deformation parameter, a calculation model for the rockmass macroscopic damage variable is proposed by introducing the JRC-JCS shear strength model for the rough crack established by Barton, which can consider the crack roughness. Secondly, the proposed calculation model is introduced into the uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack, which both considers the coupling of the macroscopic and microscopic defects, and then a uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack is established which can consider the crack roughness at the same time. Finally, the effect of crack roughness JRC and crack basic friction angle φb and crack length 2a on rockmass dynamic mechanical property is studied with the parametric sensitivity analysis. The result shows that the rockmass dynamic climax strength increases from 26.42 MPa to 27.28 and 28.37 MPa with JRC increasing from 0 to 10 and 20 respectively. The rockmass dynamic climax strength increases from 26.42 MPa to 27.28 and 28.80 MPa with φb increasing from 0° to 15° and 30° respectively. The rockmass dynamic climax strength decreases from 31.37 MPa to 27.28 and 23.90 MPa with 2a increasing from 1cm to 2 and 3cm respectively. At the same time, in order to describe the influence of the crack roughness more accurately, the crack fractal dimension is introduced into the dynamic damage model for the rock mass, which not only improves the calculation accuracy of the model, but also broadens its application range, which is more convenient for practical engineering application.
, Available online , doi: 10.11883/bzycj-2024-0227
Abstract:
The small-scale test has several advantages, such as low cost, low risk, and short duration, and has been widely applied in aerospace and other fields. Taking the lower structure of a typical civil aircraft fuselage as the research object, this study conducted theoretical analysis and experimental methodology of scaling on the impact crashworthiness of civil aircraft structures. Using a dimensional analysis, the complex dynamics of the fuselage crash were simplified to identify key physical parameters and processes. The main objects, critical physical parameters, and physical processes involved in the aircraft crash were discussed, leading to the extraction of key basic physical parameters and the derivation of primary dimensionless numbers that control the crash response of the fuselage structure. Based on the Buckingham Π theorem, the scaling factor for civil aircraft crashes was derived, establishing the small-scale experimental methodology. A 1/4 scale experimental model was designed and fabricated, and an impact test at a speed of 6 m/s was performed. The velocity, acceleration, ground impact load, deformation, and failure modes of key components in both full-scale and small-scale crash tests were obtained and compared. The applicability and accuracy of the small-scale theory in the crash experiment of the civil aircraft fuselage frame section were verified. The results show that the deformation and failure modes of the frames and columns of the 1/4 scale model are in good agreement with those of the full-scale model. The peak crash load prediction error of the small-scale structure for the full-scale prototype structure is 14.4%, the peak seat acceleration prediction error is 14.8%, and the peak acceleration prediction error at the beam is 13.1%. The small-scale tests can effectively predict the deformation, failure process, and dynamic response of key parts of the full-scale prototype structure. Therefore, the small-scale test could be used to verify and evaluate the crash performance of civil aircraft structures.
The small-scale test has several advantages, such as low cost, low risk, and short duration, and has been widely applied in aerospace and other fields. Taking the lower structure of a typical civil aircraft fuselage as the research object, this study conducted theoretical analysis and experimental methodology of scaling on the impact crashworthiness of civil aircraft structures. Using a dimensional analysis, the complex dynamics of the fuselage crash were simplified to identify key physical parameters and processes. The main objects, critical physical parameters, and physical processes involved in the aircraft crash were discussed, leading to the extraction of key basic physical parameters and the derivation of primary dimensionless numbers that control the crash response of the fuselage structure. Based on the Buckingham Π theorem, the scaling factor for civil aircraft crashes was derived, establishing the small-scale experimental methodology. A 1/4 scale experimental model was designed and fabricated, and an impact test at a speed of 6 m/s was performed. The velocity, acceleration, ground impact load, deformation, and failure modes of key components in both full-scale and small-scale crash tests were obtained and compared. The applicability and accuracy of the small-scale theory in the crash experiment of the civil aircraft fuselage frame section were verified. The results show that the deformation and failure modes of the frames and columns of the 1/4 scale model are in good agreement with those of the full-scale model. The peak crash load prediction error of the small-scale structure for the full-scale prototype structure is 14.4%, the peak seat acceleration prediction error is 14.8%, and the peak acceleration prediction error at the beam is 13.1%. The small-scale tests can effectively predict the deformation, failure process, and dynamic response of key parts of the full-scale prototype structure. Therefore, the small-scale test could be used to verify and evaluate the crash performance of civil aircraft structures.
, Available online , doi: 10.11883/bzycj-2024-0294
Abstract:
To accurately predict the initial velocity distribution of cylindrical casing under central point detonation at one end with different length-diameter ratios (L/D), it studied the impact of L/D ratios on the initial velocity of fragments and the applicability of existing empirical models for the initial velocity of fragments founded on the numerical model of experimental verification. On this basis, a correction term related to L/D ratio, which was often influenced by the axial rarefaction waves, was added to the fragment initial velocity index model. By fitting the data obtained from numerical simulations, the function expression of the correction term was derived and the calculation model for the initial velocity distribution of cylindrical casing with L/D ratio≥1 was obtained. Finally, the applicability of the established fragment initial velocity calculation model was validated through experimental data and numerical simulations. The research results indicate that the initial velocity distribution of fragments under different L/D ratios exhibits a trend where the initial velocities are lower at both ends and higher in the middle. Additionally, as the L/D ratio raises, the initial velocity of the fragment also increases. When the L/D ratio reaches 5, the relative error between the maximum initial velocity of the fragments and the calculated result using the Gurney formula is only 1.99%. However, the existing models for calculating initial velocities of fragment display significant errors when predicting smaller L/D ratios in cylindrical casing. The average error between the formula calculation results and the experimental and numerical simulation results does not exceed 6%, indicating that the proposed model is reliable for predicting the initial velocity distribution of fragments under different L/D ratios.
To accurately predict the initial velocity distribution of cylindrical casing under central point detonation at one end with different length-diameter ratios (L/D), it studied the impact of L/D ratios on the initial velocity of fragments and the applicability of existing empirical models for the initial velocity of fragments founded on the numerical model of experimental verification. On this basis, a correction term related to L/D ratio, which was often influenced by the axial rarefaction waves, was added to the fragment initial velocity index model. By fitting the data obtained from numerical simulations, the function expression of the correction term was derived and the calculation model for the initial velocity distribution of cylindrical casing with L/D ratio≥1 was obtained. Finally, the applicability of the established fragment initial velocity calculation model was validated through experimental data and numerical simulations. The research results indicate that the initial velocity distribution of fragments under different L/D ratios exhibits a trend where the initial velocities are lower at both ends and higher in the middle. Additionally, as the L/D ratio raises, the initial velocity of the fragment also increases. When the L/D ratio reaches 5, the relative error between the maximum initial velocity of the fragments and the calculated result using the Gurney formula is only 1.99%. However, the existing models for calculating initial velocities of fragment display significant errors when predicting smaller L/D ratios in cylindrical casing. The average error between the formula calculation results and the experimental and numerical simulation results does not exceed 6%, indicating that the proposed model is reliable for predicting the initial velocity distribution of fragments under different L/D ratios.
, Available online , doi: 10.11883/bzycj-2024-0214
Abstract:
To understand the relationship between fragmentation and energy dissipation in copper-bearing ore rock subjected to impact loading, a split Hopkinson pressure bar (SHPB) testing apparatus was employed to study the mechanical properties and energy transfer mechanisms of copper-bearing tuff under varying impact loads. Additionally, fractal theory was used to establish the correlation between dissipated energy and rock fragmentation. Utilizing the finite discrete element method (FDEM), numerical simulations of crack propagation within the rock were conducted. The results indicate that as the incident energy increases, the distribution patterns of the transmission energy, absorbed energy and reflection energy remain consistent, which are characterized by transmission energy, absorbed energy and reflection energy decreased successively. Furthermore, significant variations in fragment size distribution are observed with changes in dissipated energy. Specifically, as dissipated energy increases from 19.52 J to 105.72 J, the average fragment size decreases from 27.98 mm to 16.94 mm, while the fractal dimension increases by 26.43%. This suggests that higher dissipated energy results in more extensive macroscopic fragmentation, an increase in the number of fragments, smaller particle sizes and enhanced uniformity. As the impact load intensifies, the time to crack initiation decreases, and the proportion of tensile cracks relative to total cracks increases. The application of the FDEM offers new insights into the fracture and failure characteristics of rocks.
To understand the relationship between fragmentation and energy dissipation in copper-bearing ore rock subjected to impact loading, a split Hopkinson pressure bar (SHPB) testing apparatus was employed to study the mechanical properties and energy transfer mechanisms of copper-bearing tuff under varying impact loads. Additionally, fractal theory was used to establish the correlation between dissipated energy and rock fragmentation. Utilizing the finite discrete element method (FDEM), numerical simulations of crack propagation within the rock were conducted. The results indicate that as the incident energy increases, the distribution patterns of the transmission energy, absorbed energy and reflection energy remain consistent, which are characterized by transmission energy, absorbed energy and reflection energy decreased successively. Furthermore, significant variations in fragment size distribution are observed with changes in dissipated energy. Specifically, as dissipated energy increases from 19.52 J to 105.72 J, the average fragment size decreases from 27.98 mm to 16.94 mm, while the fractal dimension increases by 26.43%. This suggests that higher dissipated energy results in more extensive macroscopic fragmentation, an increase in the number of fragments, smaller particle sizes and enhanced uniformity. As the impact load intensifies, the time to crack initiation decreases, and the proportion of tensile cracks relative to total cracks increases. The application of the FDEM offers new insights into the fracture and failure characteristics of rocks.
, Available online , doi: 10.11883/bzycj-2024-0403
Abstract:
The shear mechanical properties and deformation damage mechanism of the double structural planes of traditional anchor cables and new anchor cables with C-shaped tube structures (abbreviated as ACC) under different loading rate conditions were investigated through experimental and numerical simulation analyses. Dual structural face shear tests were conducted at shear displacement loading rates of 2, 10, 20, 30, and 40 mm/min under 55 MPa concrete specimen strength and 200 kN preload, with shear deformation curves, peak structural shear loads, steel wire damage patterns, and structural plane shear strength contributions as the main parameters considered. The results show that the loading rate significantly affects the shear performance of the structure. Within a certain loading rate interval, influenced by the damage accumulation rate and the strain rate strengthening effect, the structure exhibits characteristics of strength weakening and strengthening, respectively, with a large variation interval in shear load-carrying capacity. Near the structural plane, the support structure shows a combination of tensile and shear damage. However, the ACC structure, due to the presence of the C-shaped tube, exhibits lower stress concentration effects, reduced fluctuation in the test curve, and significantly weakened internal steel wire damage compared to traditional anchor cables. Meanwhile, the numerical model of the double shear test of the ACC structure, constructed based on the test results, exhibits high accuracy. Numerical simulations of dynamic loading tests demonstrate that the anchoring system formed by the ACC structure has a good energy absorption effect, which becomes more pronounced with increasing impact energy. Under high-speed impact, the ACC structure is significantly affected by the strain rate reinforcement effect, with higher shear load capacity at greater impact velocities.
The shear mechanical properties and deformation damage mechanism of the double structural planes of traditional anchor cables and new anchor cables with C-shaped tube structures (abbreviated as ACC) under different loading rate conditions were investigated through experimental and numerical simulation analyses. Dual structural face shear tests were conducted at shear displacement loading rates of 2, 10, 20, 30, and 40 mm/min under 55 MPa concrete specimen strength and 200 kN preload, with shear deformation curves, peak structural shear loads, steel wire damage patterns, and structural plane shear strength contributions as the main parameters considered. The results show that the loading rate significantly affects the shear performance of the structure. Within a certain loading rate interval, influenced by the damage accumulation rate and the strain rate strengthening effect, the structure exhibits characteristics of strength weakening and strengthening, respectively, with a large variation interval in shear load-carrying capacity. Near the structural plane, the support structure shows a combination of tensile and shear damage. However, the ACC structure, due to the presence of the C-shaped tube, exhibits lower stress concentration effects, reduced fluctuation in the test curve, and significantly weakened internal steel wire damage compared to traditional anchor cables. Meanwhile, the numerical model of the double shear test of the ACC structure, constructed based on the test results, exhibits high accuracy. Numerical simulations of dynamic loading tests demonstrate that the anchoring system formed by the ACC structure has a good energy absorption effect, which becomes more pronounced with increasing impact energy. Under high-speed impact, the ACC structure is significantly affected by the strain rate reinforcement effect, with higher shear load capacity at greater impact velocities.
Preparation of NiP@Fe-SBA-15 suppressant and its inhibition mechanism on PP dust deflagration flames
, Available online , doi: 10.11883/bzycj-2024-0434
Abstract:
Polypropylene (PP) is widely utilized in industrial production, yet PP dust generated during its production and transportation can form explosive dust clouds, leading to severe dust explosion accidents that threaten personnel and equipment safety. To address this issue, a novel explosion suppressant, NiP@Fe-SBA-15, was synthesized to inhibit the propagation of PP dust combustion flames. The synthesis involved modifying SBA-15 mesoporous silica with Fe ions and subsequently loading NiP, resulting in a composite powder with uniformly dispersed active components and a well-preserved mesoporous structure. Characterization via SEM-Mapping and N2 adsorption-desorption experiments revealed that NiP@Fe-SBA-15 maintains a high specific surface area, exhibits a regulated pore structure, and shows no significant particle agglomeration. The Hartman tube explosive testing system was employed to evaluate the effect of NiP@Fe-SBA-15 on PP dust deflagration. Results indicated that as the NiP@Fe-SBA-15 additive increased, the flame propagation speed, brightness, and flame length of PP deflagration decreased significantly, with flame propagation almost completely inhibited at a suppressant dosage of 70 wt%. The dual explosion suppression mechanism of NiP@Fe-SBA-15 was analyzed. Physically, NiP@Fe-SBA-15 occupies reaction space, reducing oxygen and combustible volatile concentrations, while the SBA-15 molecular sieve, exposed by thermal decomposition of the suppressant, absorbs heat and forms a physical barrier, thereby reducing combustion intensity. Chemically, NiP decomposition releases Ni· and P· radicals that consume key free radicals (H·, O·, OH·) in combustion reactions, interrupting explosion chain reactions. Meanwhile, Fe-based species rapidly oxidize to Fe3O4, reducing oxygen availability and further weakening combustion intensity. In summary, NiP@Fe-SBA-15 was proven to be an effective explosion suppressant for PP dust explosions, reducing combustion intensity through combined physicochemical synergies. This research provides a new approach to enhancing polypropylene industry safety. Future work will focus on optimizing the industrial application of NiP@Fe-SBA-15 explosion suppressants while addressing cost, environmental sustainability, and stability issues to further advance dust explosion prevention technology.
Polypropylene (PP) is widely utilized in industrial production, yet PP dust generated during its production and transportation can form explosive dust clouds, leading to severe dust explosion accidents that threaten personnel and equipment safety. To address this issue, a novel explosion suppressant, NiP@Fe-SBA-15, was synthesized to inhibit the propagation of PP dust combustion flames. The synthesis involved modifying SBA-15 mesoporous silica with Fe ions and subsequently loading NiP, resulting in a composite powder with uniformly dispersed active components and a well-preserved mesoporous structure. Characterization via SEM-Mapping and N2 adsorption-desorption experiments revealed that NiP@Fe-SBA-15 maintains a high specific surface area, exhibits a regulated pore structure, and shows no significant particle agglomeration. The Hartman tube explosive testing system was employed to evaluate the effect of NiP@Fe-SBA-15 on PP dust deflagration. Results indicated that as the NiP@Fe-SBA-15 additive increased, the flame propagation speed, brightness, and flame length of PP deflagration decreased significantly, with flame propagation almost completely inhibited at a suppressant dosage of 70 wt%. The dual explosion suppression mechanism of NiP@Fe-SBA-15 was analyzed. Physically, NiP@Fe-SBA-15 occupies reaction space, reducing oxygen and combustible volatile concentrations, while the SBA-15 molecular sieve, exposed by thermal decomposition of the suppressant, absorbs heat and forms a physical barrier, thereby reducing combustion intensity. Chemically, NiP decomposition releases Ni· and P· radicals that consume key free radicals (H·, O·, OH·) in combustion reactions, interrupting explosion chain reactions. Meanwhile, Fe-based species rapidly oxidize to Fe3O4, reducing oxygen availability and further weakening combustion intensity. In summary, NiP@Fe-SBA-15 was proven to be an effective explosion suppressant for PP dust explosions, reducing combustion intensity through combined physicochemical synergies. This research provides a new approach to enhancing polypropylene industry safety. Future work will focus on optimizing the industrial application of NiP@Fe-SBA-15 explosion suppressants while addressing cost, environmental sustainability, and stability issues to further advance dust explosion prevention technology.
, Available online , doi: 10.11883/bzycj-2024-0359
Abstract:
Oxy-fuel combustion is one of the effective means to reduce greenhouse gases. To grasp the combustion characteristics of the clean fuel acetylene in O2/CO2 atmosphere and to investigate the effect of different CO2 volume fraction on the lower flammable limit of acetylene, the lower flammable limit of acetylene was experimentally measured in a 5 L cylindrical explosive reaction device. With the increase of CO2 volume fraction from 14% to 85%, the experimental value of the lower flammable limit of acetylene increased from 2.64% to 3.93%, which was linearly increased in a small range. Compared with hydrocarbon fuels such as ethylene, ethane, and propylene, the lower flammability limit of alkanes, olefins, alkynes decrease sequentially, indicating that alkynes have a larger combustion range and a higher hazard factor. Based on the calculation model of limiting laminar flame velocity method, a prediction model applicable to the lower flammability limit of acetylene was established. Through the verification of experimental data, the average absolute error of this prediction model using the USC Ⅱ combustion reaction mechanism is at 0.52%, and the model is accurate and reliable. To explain the reason for the existence of the lower flammability limit from the perspective of the competition between the temperature rise of the heat generation from fuel consumption and the temperature drop of the heat dissipation from the expansion of the fuel body, this study examines the thermodynamic, chemical, and transport effects of CO2 on the lower flammability limit. The combustion reaction mechanism of USC Ⅱ is modified to incorporate the virtual substances FCO2, TCO2, and MCO2, and comparing the flammability limits of the three virtual substances as well as those of the five atmospheres of N2 and CO2. The thermodynamic, chemical and transport effects of CO2 on the lower flammability limit were discussed. The results show that the average proportion of thermodynamic effect is 64%, chemical effect is 35% and transportation effect is 1%.
Oxy-fuel combustion is one of the effective means to reduce greenhouse gases. To grasp the combustion characteristics of the clean fuel acetylene in O2/CO2 atmosphere and to investigate the effect of different CO2 volume fraction on the lower flammable limit of acetylene, the lower flammable limit of acetylene was experimentally measured in a 5 L cylindrical explosive reaction device. With the increase of CO2 volume fraction from 14% to 85%, the experimental value of the lower flammable limit of acetylene increased from 2.64% to 3.93%, which was linearly increased in a small range. Compared with hydrocarbon fuels such as ethylene, ethane, and propylene, the lower flammability limit of alkanes, olefins, alkynes decrease sequentially, indicating that alkynes have a larger combustion range and a higher hazard factor. Based on the calculation model of limiting laminar flame velocity method, a prediction model applicable to the lower flammability limit of acetylene was established. Through the verification of experimental data, the average absolute error of this prediction model using the USC Ⅱ combustion reaction mechanism is at 0.52%, and the model is accurate and reliable. To explain the reason for the existence of the lower flammability limit from the perspective of the competition between the temperature rise of the heat generation from fuel consumption and the temperature drop of the heat dissipation from the expansion of the fuel body, this study examines the thermodynamic, chemical, and transport effects of CO2 on the lower flammability limit. The combustion reaction mechanism of USC Ⅱ is modified to incorporate the virtual substances FCO2, TCO2, and MCO2, and comparing the flammability limits of the three virtual substances as well as those of the five atmospheres of N2 and CO2. The thermodynamic, chemical and transport effects of CO2 on the lower flammability limit were discussed. The results show that the average proportion of thermodynamic effect is 64%, chemical effect is 35% and transportation effect is 1%.
, Available online , doi: 10.11883/bzycj-2024-0431
Abstract:
Compared to concrete and steel structures, research on the blast resistance of timber structures is relatively scarce. Although experimental studies on the blast performance of light-frame wood walls have been conducted, relevant numerical studies remain limited. This study addresses the numerical modeling of light-frame wood walls under blast loads, with a focus on the determination of the dynamic increase factor (DIF) for nail connections and the failure criteria for wood studs. Based on the partial composite action theory, an analytical expression was derived to describe the relationship between the DIF for nail connections and other mechanical properties of light-frame wood walls, including the stiffness of studs, the stiffness of sheathing panels, and the stiffness of nail connections. A reasonable value for the DIF of nail connections was provided by introducing experimentally measured DIFs for wood studs and wood-frame walls. On this basis, a finite element (FE) model for blast resistance analysis of light-frame wood walls was developed. In this model, the wood studs, sheathing panels, and nail connections were represented using beam elements, shell elements, and discrete beam elements, respectively. The orthotropic characteristics of wood-based structural panels, the nonlinear dynamic behavior of nail connections, and the dynamic elastic-plastic features of wood studs were also appropriately modeled. Verification of the developed model against experimental data indicates that it can accurately predict the dynamic response of light-frame wood walls under blast loads, as well as the time and corresponding peak displacement when wood studs fracture. FE analyses also show that if the variation of the studs’ material properties is reasonably accounted for, the predictions of the dynamic response and failure mode after the fracture of studs are in good agreement with the experimental results. The developed model paves the way for assessing the blast vulnerability of light-frame wood structures in future research.
Compared to concrete and steel structures, research on the blast resistance of timber structures is relatively scarce. Although experimental studies on the blast performance of light-frame wood walls have been conducted, relevant numerical studies remain limited. This study addresses the numerical modeling of light-frame wood walls under blast loads, with a focus on the determination of the dynamic increase factor (DIF) for nail connections and the failure criteria for wood studs. Based on the partial composite action theory, an analytical expression was derived to describe the relationship between the DIF for nail connections and other mechanical properties of light-frame wood walls, including the stiffness of studs, the stiffness of sheathing panels, and the stiffness of nail connections. A reasonable value for the DIF of nail connections was provided by introducing experimentally measured DIFs for wood studs and wood-frame walls. On this basis, a finite element (FE) model for blast resistance analysis of light-frame wood walls was developed. In this model, the wood studs, sheathing panels, and nail connections were represented using beam elements, shell elements, and discrete beam elements, respectively. The orthotropic characteristics of wood-based structural panels, the nonlinear dynamic behavior of nail connections, and the dynamic elastic-plastic features of wood studs were also appropriately modeled. Verification of the developed model against experimental data indicates that it can accurately predict the dynamic response of light-frame wood walls under blast loads, as well as the time and corresponding peak displacement when wood studs fracture. FE analyses also show that if the variation of the studs’ material properties is reasonably accounted for, the predictions of the dynamic response and failure mode after the fracture of studs are in good agreement with the experimental results. The developed model paves the way for assessing the blast vulnerability of light-frame wood structures in future research.
, Available online , doi: 10.11883/bzycj-2024-0272
Abstract:
In order to study the dynamic mechanical properties of concrete and the dynamic temperature at the crack under impact, steel-polypropylene fiber reinforced concrete (SPFRC) was taken as the research object using a self-built high-speed infrared temperature measurement system. The time resolution of the high-speed infrared temperature measurement system is in the order of microsecond. The concrete temperature curve was fitted by static calibration test as a reference. Combined with the Hopkinson pressure bar test device, the dynamic properties of SPFRC specimens with different steel fiber contents and the dynamic temperature change at the crack were studied. The results indicate a significant coupling effect between the temperature evolution and mechanical properties of the concrete specimens and substantial influences of the steel fiber content on both dynamic performance and temperature. Specifically, as the steel fiber content increases, the compressive strength of the concrete improves, reaching optimal mechanical performance at 1.5% steel fiber content. However, at 2.0% steel fiber content, the mechanical performance slightly decreases due to an increase in internal voids within the concrete. During impact, the dynamic temperature effect at the crack location exhibits a “stepped” pattern, with temperature change occurring in two distinct stages: an initial slow rise during early crack formation, followed by a sharp increase as friction and shear effects intensify with crack propagation. The influence of varying steel fiber content on temperature change is limited, with peak temperature and peak stress showing similar trends. The primary temperature variations are driven by crack propagation and frictional effects. After impact, the overall temperature in SPFRC specimens continues to rise within the first 300 μs. Due to the thermal lag, the temperature does not decrease immediately after unloading. The high-speed infrared temperature measurement system provides a new method for real-time monitoring of temperature changes at concrete crack locations, offering a basis for assessing temperature evolution at cracks and the evaluation of crack propagation behavior.
In order to study the dynamic mechanical properties of concrete and the dynamic temperature at the crack under impact, steel-polypropylene fiber reinforced concrete (SPFRC) was taken as the research object using a self-built high-speed infrared temperature measurement system. The time resolution of the high-speed infrared temperature measurement system is in the order of microsecond. The concrete temperature curve was fitted by static calibration test as a reference. Combined with the Hopkinson pressure bar test device, the dynamic properties of SPFRC specimens with different steel fiber contents and the dynamic temperature change at the crack were studied. The results indicate a significant coupling effect between the temperature evolution and mechanical properties of the concrete specimens and substantial influences of the steel fiber content on both dynamic performance and temperature. Specifically, as the steel fiber content increases, the compressive strength of the concrete improves, reaching optimal mechanical performance at 1.5% steel fiber content. However, at 2.0% steel fiber content, the mechanical performance slightly decreases due to an increase in internal voids within the concrete. During impact, the dynamic temperature effect at the crack location exhibits a “stepped” pattern, with temperature change occurring in two distinct stages: an initial slow rise during early crack formation, followed by a sharp increase as friction and shear effects intensify with crack propagation. The influence of varying steel fiber content on temperature change is limited, with peak temperature and peak stress showing similar trends. The primary temperature variations are driven by crack propagation and frictional effects. After impact, the overall temperature in SPFRC specimens continues to rise within the first 300 μs. Due to the thermal lag, the temperature does not decrease immediately after unloading. The high-speed infrared temperature measurement system provides a new method for real-time monitoring of temperature changes at concrete crack locations, offering a basis for assessing temperature evolution at cracks and the evaluation of crack propagation behavior.
, Available online , doi: 10.11883/bzycj-2024-0250
Abstract:
In the process of deep penetration of the earth penetration weapon (EPW) attacking the underground target, the non-ideal penetration attitude with an initial attack angle is inevitable, which will introduce transverse overload with a large peak value for the earth penetrator. It could damage some important components of the earth-penetrating projectile and reduce the penetration efficiency of the projectile. Therefore, it is necessary to study the methodology of reducing the transverse overload peak value of the earth-penetrating projectile. However, the previous research on the earth-penetrating projectile seldom considered the influence of transverse overload, making it difficult to effectively reduce the transverse overload. In order to overcome this problem, a numerical simulation method was used to study the special transverse overload shedding effect and its mechanism of a new type of earth-penetrating projectile with a serrated configuration penetrating concrete targets at non-zero attack angles. The influences of the initial attack angle and the coefficient of the center of mass of the projectile were studied, and the motion, contact force, contact moment, and contact area of the projectile were analyzed using a conventional smooth projectile for comparison. The results show that for small initial attack angles of 1°, 2° and 3°, the peak value of transverse overload of the serrated projectile is reduced by about 30.6%, 5.2%, and 11.3%, respectively, compared to the smooth projectile but the peak value of contact moment, pulse width, and deflection angle are increased. The research reveals the mechanical mechanism to reduce transverse overload: the serrated body of the projectile reduces the contact area between the projectile and the target, and the transverse contact force is mainly concentrated on the upper surface of the right serrated parts of the first two serrated grooves near the head of the projectile; the transverse contact force between the serrated body and the target decreases, while the transverse contact force between the non-serrated parts (mainly the head of the projectile) and the target increases. Therefore, these two parts of the projectile compete and control the reduction effects of the transverse overload of the whole projectile in the process of deep penetration with an initial attack angle. When optimizations of structural design are used to suppress the ballistic deflection of the serrated projectile, the transverse overload shedding efficiency of serrated projectiles can be effectively improved.
In the process of deep penetration of the earth penetration weapon (EPW) attacking the underground target, the non-ideal penetration attitude with an initial attack angle is inevitable, which will introduce transverse overload with a large peak value for the earth penetrator. It could damage some important components of the earth-penetrating projectile and reduce the penetration efficiency of the projectile. Therefore, it is necessary to study the methodology of reducing the transverse overload peak value of the earth-penetrating projectile. However, the previous research on the earth-penetrating projectile seldom considered the influence of transverse overload, making it difficult to effectively reduce the transverse overload. In order to overcome this problem, a numerical simulation method was used to study the special transverse overload shedding effect and its mechanism of a new type of earth-penetrating projectile with a serrated configuration penetrating concrete targets at non-zero attack angles. The influences of the initial attack angle and the coefficient of the center of mass of the projectile were studied, and the motion, contact force, contact moment, and contact area of the projectile were analyzed using a conventional smooth projectile for comparison. The results show that for small initial attack angles of 1°, 2° and 3°, the peak value of transverse overload of the serrated projectile is reduced by about 30.6%, 5.2%, and 11.3%, respectively, compared to the smooth projectile but the peak value of contact moment, pulse width, and deflection angle are increased. The research reveals the mechanical mechanism to reduce transverse overload: the serrated body of the projectile reduces the contact area between the projectile and the target, and the transverse contact force is mainly concentrated on the upper surface of the right serrated parts of the first two serrated grooves near the head of the projectile; the transverse contact force between the serrated body and the target decreases, while the transverse contact force between the non-serrated parts (mainly the head of the projectile) and the target increases. Therefore, these two parts of the projectile compete and control the reduction effects of the transverse overload of the whole projectile in the process of deep penetration with an initial attack angle. When optimizations of structural design are used to suppress the ballistic deflection of the serrated projectile, the transverse overload shedding efficiency of serrated projectiles can be effectively improved.
, Available online , doi: 10.11883/bzycj-2024-0093
Abstract:
Explosion experiments utilizing a 20 L spherical explosion apparatus were conducted to investigate the explosion characteristics of aluminum and aluminum-silicon alloy powders, prevalent in additive manufacturing. The tested samples included Al, Al-12Si, and Al-20Si. Various parameters were measured under different influencing factors, including the lower explosion limit, maximum explosion pressure, maximum pressure rise rate, explosion temperature, and time to reach peak temperature. Thermogravimetric analysis-differential scanning calorimetry was employed to analyze the thermal oxidation properties of the samples. The results indicated that an increase in the silicon content within the alloy corresponded with a lower explosion limit. Conversely, the maximum explosion pressure and peak temperature showed a downward trend. Meanwhile. a reduction in the maximum pressure rise rate was observed. The exothermic amount of the oxidation process reduced, and the oxidation rate slowed down. The concentrations at which the three samples reached the maximum explosion pressure and peak temperature were 300 g/m3 for Al, 750 g/m3 for Al-12Si, and 900 g/m3 for Al-20Si, respectively. When the ignition energy increased, the rate of increase in maximum explosion pressure for the aluminum-silicon alloys was lower than that for aluminum powder. The effect of environmental temperature changes on the lower explosive limit was less significant compared to that of particle size variations. As the environmental temperature increased, the explosion pressure did not show a significant change, while the pressure rise rate increased slightly. X-ray diffraction analysis of the explosion products revealed that, in addition to Al2O3 and Al, the explosion products of the aluminum-silicon alloys also contained SiO2 and Si. This indicates that the Si element in the alloy participated in the explosion reaction. It confirms that the explosion of aluminum-silicon alloy powder is caused by the heating and vaporization of the particles, leading to the formation of a combustible gas composed of gaseous aluminum and silicon, which then combusts with oxygen.
Explosion experiments utilizing a 20 L spherical explosion apparatus were conducted to investigate the explosion characteristics of aluminum and aluminum-silicon alloy powders, prevalent in additive manufacturing. The tested samples included Al, Al-12Si, and Al-20Si. Various parameters were measured under different influencing factors, including the lower explosion limit, maximum explosion pressure, maximum pressure rise rate, explosion temperature, and time to reach peak temperature. Thermogravimetric analysis-differential scanning calorimetry was employed to analyze the thermal oxidation properties of the samples. The results indicated that an increase in the silicon content within the alloy corresponded with a lower explosion limit. Conversely, the maximum explosion pressure and peak temperature showed a downward trend. Meanwhile. a reduction in the maximum pressure rise rate was observed. The exothermic amount of the oxidation process reduced, and the oxidation rate slowed down. The concentrations at which the three samples reached the maximum explosion pressure and peak temperature were 300 g/m3 for Al, 750 g/m3 for Al-12Si, and 900 g/m3 for Al-20Si, respectively. When the ignition energy increased, the rate of increase in maximum explosion pressure for the aluminum-silicon alloys was lower than that for aluminum powder. The effect of environmental temperature changes on the lower explosive limit was less significant compared to that of particle size variations. As the environmental temperature increased, the explosion pressure did not show a significant change, while the pressure rise rate increased slightly. X-ray diffraction analysis of the explosion products revealed that, in addition to Al2O3 and Al, the explosion products of the aluminum-silicon alloys also contained SiO2 and Si. This indicates that the Si element in the alloy participated in the explosion reaction. It confirms that the explosion of aluminum-silicon alloy powder is caused by the heating and vaporization of the particles, leading to the formation of a combustible gas composed of gaseous aluminum and silicon, which then combusts with oxygen.
, Available online , doi: 10.11883/bzycj-2024-0159
Abstract:
To exploring the dynamic response characteristics of the shed-tunnel structure under multiple rockfall impacts, an FEM-SPH coupled numerical model is established based on ANSYS/LS-DYNA and is also tested with the data before. Then, the model is combined with the full restart technique to study the effects of the shed-tunnel structure dynamic response under multiple rockfall impacts by considering four factors, e.g., rockfall impact velocity, rockfall mass, impact angle and rockfall shape. The results show that the impact force, buffer top impact displacement, roof displacement and plastic strain of the shed-tunnel are positively correlated with the rockfall mass, velocity and angle. The impact force, roof displacement and plastic strain of the shed-tunnel structure generated by the cuboid rockfall impact are all larger than those of the spherical rockfall, and the impact displacement generated by the spherical rockfall impact is larger than that of the cuboid. For the cuboid rockfall, the impact displacement, roof displacement and plastic strain are negatively correlated with the contact area. Under the multiple rockfall impacts, the peak impact force usually increases firstly and then tends to be stable.
To exploring the dynamic response characteristics of the shed-tunnel structure under multiple rockfall impacts, an FEM-SPH coupled numerical model is established based on ANSYS/LS-DYNA and is also tested with the data before. Then, the model is combined with the full restart technique to study the effects of the shed-tunnel structure dynamic response under multiple rockfall impacts by considering four factors, e.g., rockfall impact velocity, rockfall mass, impact angle and rockfall shape. The results show that the impact force, buffer top impact displacement, roof displacement and plastic strain of the shed-tunnel are positively correlated with the rockfall mass, velocity and angle. The impact force, roof displacement and plastic strain of the shed-tunnel structure generated by the cuboid rockfall impact are all larger than those of the spherical rockfall, and the impact displacement generated by the spherical rockfall impact is larger than that of the cuboid. For the cuboid rockfall, the impact displacement, roof displacement and plastic strain are negatively correlated with the contact area. Under the multiple rockfall impacts, the peak impact force usually increases firstly and then tends to be stable.
, Available online , doi: 10.11883/bzycj-2024-0361
Abstract:
To study the damage law of calcareous conglomerate under blasting, firstly, the damage fracture process and mechanism of calcareous conglomerate under blasting load were revealed based on the theory of damage fracture mechanics. A meso-scale model of conglomerate, including filler, conglomerate and interfacial transition zone (ITZ), was established by using LS-DYNA and Fortran programming, and the propagation law of explosive stress wave and its damage characteristics were analyzed. The damage fracture process of calcareous conglomerate under blasting can be divided into four stages, namely: compression damage in both gravel and fill; tensile damage in gravel and compression damage in fill; tensile damage in both gravel and fill; and tensile damage at the intersection of gravel and fill. Numerical results show that under blasting loads, the gravel has higher equivalent stresses, the fill has the lowest, stress concentration is evident at the ITZ, and the stress gap between the gravel and the fill decreases as the distance increases. The conglomerate sustains relatively minor damage, with a notable phenomenon of damage occurring around it. However, and the filler experiences significant damage. The expansion of blasting crack in Calcareous conglomerate forms mainly along the direction of stress wave propagation. Cracks tend to develop along the filler with lower physical and mechanical properties, as well as along the junction surfaces. The damage to the gravel is comparatively less severe. Blasting blockiness is mainly manifested as the filler wrapping gravel, and the distribution of blasting blockiness is affected by the bonding force at the intersection surface and the distribution of gravel.
To study the damage law of calcareous conglomerate under blasting, firstly, the damage fracture process and mechanism of calcareous conglomerate under blasting load were revealed based on the theory of damage fracture mechanics. A meso-scale model of conglomerate, including filler, conglomerate and interfacial transition zone (ITZ), was established by using LS-DYNA and Fortran programming, and the propagation law of explosive stress wave and its damage characteristics were analyzed. The damage fracture process of calcareous conglomerate under blasting can be divided into four stages, namely: compression damage in both gravel and fill; tensile damage in gravel and compression damage in fill; tensile damage in both gravel and fill; and tensile damage at the intersection of gravel and fill. Numerical results show that under blasting loads, the gravel has higher equivalent stresses, the fill has the lowest, stress concentration is evident at the ITZ, and the stress gap between the gravel and the fill decreases as the distance increases. The conglomerate sustains relatively minor damage, with a notable phenomenon of damage occurring around it. However, and the filler experiences significant damage. The expansion of blasting crack in Calcareous conglomerate forms mainly along the direction of stress wave propagation. Cracks tend to develop along the filler with lower physical and mechanical properties, as well as along the junction surfaces. The damage to the gravel is comparatively less severe. Blasting blockiness is mainly manifested as the filler wrapping gravel, and the distribution of blasting blockiness is affected by the bonding force at the intersection surface and the distribution of gravel.
, Available online , doi: 10.11883/bzycj-2024-0232
Abstract:
Applicable buffer-head covers and various open-cell foam buffer configurations were designed to meet the buffering and load reduction challenges during high-speed water entry vehicles. In the arbitrary Lagrangian-Euler method, the grid can move as the material flows within the spatial grid. This unique feature allows the arbitrary Lagrangian-Euler method to harness the advantages of both the Lagrangian and Euler methods. It not only overcomes numerical calculation challenges stemming from element distortion but also facilitates accurate computation of large deformations and displacements in solids and fluids. This makes it particularly well-suited for addressing high-speed water buffer load reduction problems. Based on the arbitrary Lagrangian-Eulerian method and considering the large deformation of the buffer foam and the hood, a numerical calculation model for buffering and load reduction during high-speed water entry of navigational bodies was established. Through numerical simulations, an in-depth study was conducted on the load reduction performance of buffer foams with different open-cell patterns. The results indicate that open-cell buffer foam exhibits significant advantages in dispersing the impact force and absorbing impact energy during water entry of navigational bodies, offering better buffering effects. Simultaneously, the buffer head cover experiences local progressive fragmentation upon water entry. The deformation and rupture of the outer wall surface of the buffer head cover at the connector between the buffer shell and the navigational body are caused by the stress concentration distribution generated during water impact. When the open-cell foam contacts the water surface, the front part enters the collapse stage, absorbing a large amount of energy and undergoing plastic deformation, resulting in a reduction of pores. This stage is the primary energy absorption phase for the buffer foam. In comparison, closed-cell foam exhibits poorer load reduction performance. Therefore, the adoption of open-cell foam represents a superior solution for buffering and load reduction during high-speed water entry of navigational bodies.
Applicable buffer-head covers and various open-cell foam buffer configurations were designed to meet the buffering and load reduction challenges during high-speed water entry vehicles. In the arbitrary Lagrangian-Euler method, the grid can move as the material flows within the spatial grid. This unique feature allows the arbitrary Lagrangian-Euler method to harness the advantages of both the Lagrangian and Euler methods. It not only overcomes numerical calculation challenges stemming from element distortion but also facilitates accurate computation of large deformations and displacements in solids and fluids. This makes it particularly well-suited for addressing high-speed water buffer load reduction problems. Based on the arbitrary Lagrangian-Eulerian method and considering the large deformation of the buffer foam and the hood, a numerical calculation model for buffering and load reduction during high-speed water entry of navigational bodies was established. Through numerical simulations, an in-depth study was conducted on the load reduction performance of buffer foams with different open-cell patterns. The results indicate that open-cell buffer foam exhibits significant advantages in dispersing the impact force and absorbing impact energy during water entry of navigational bodies, offering better buffering effects. Simultaneously, the buffer head cover experiences local progressive fragmentation upon water entry. The deformation and rupture of the outer wall surface of the buffer head cover at the connector between the buffer shell and the navigational body are caused by the stress concentration distribution generated during water impact. When the open-cell foam contacts the water surface, the front part enters the collapse stage, absorbing a large amount of energy and undergoing plastic deformation, resulting in a reduction of pores. This stage is the primary energy absorption phase for the buffer foam. In comparison, closed-cell foam exhibits poorer load reduction performance. Therefore, the adoption of open-cell foam represents a superior solution for buffering and load reduction during high-speed water entry of navigational bodies.
, Available online , doi: 10.11883/bzycj-2024-0112
Abstract:
Research on blasting craters is one of the most fundamental studies in blasting engineering. To elucidate the formation process and mechanisms of blasting craters and to investigate the roles of blasting stress waves and explosion gases in rock fragmentation during this process, a blasting load model was developed. This model is based on a double-exponential explosive load function and the equation of state for explosion gas pressure, incorporating the dynamic-static sequential effects of blasting. By combining the distinct loading characteristics of blasting stress waves and explosion gases, a discrete element numerical model of the blasting crater was established to simulate the development of fractures, rock fragmentation, and ejection of blasted rock. Simulations were performed both with and without the inclusion of explosion gas loading to explore the respective contributions of blasting stress waves and explosion gases to crater formation. The results show that the blasting crater dimensions simulated with the dynamic-static sequential loading model align closely with field test results, accurately capturing the formation and evolution of fractures in the blasting zone and the ejection behavior of fragmented rock. The high loading rate of blasting stress waves is the primary cause of ring-shaped microfractures in the near-field region of the explosion source, which can also induce reflective tensile damage, forming “slice drop” failure at free surfaces. Explosion gases, on the other hand, are the main drivers of radially extensive fractures in the far-field region of the explosion source and propel fragmented rock outward at a high velocity. Explosion gases exhibit not only quasi-static effects but also dynamic effects, extending the duration of blasting vibrations and amplifying the peak vibration velocity. The development of fractures during crater formation can be broadly categorized into three stages: stress wave-induced fracturing, explosion gas-induced fracturing, and deformation energy release-induced fracturing.
Research on blasting craters is one of the most fundamental studies in blasting engineering. To elucidate the formation process and mechanisms of blasting craters and to investigate the roles of blasting stress waves and explosion gases in rock fragmentation during this process, a blasting load model was developed. This model is based on a double-exponential explosive load function and the equation of state for explosion gas pressure, incorporating the dynamic-static sequential effects of blasting. By combining the distinct loading characteristics of blasting stress waves and explosion gases, a discrete element numerical model of the blasting crater was established to simulate the development of fractures, rock fragmentation, and ejection of blasted rock. Simulations were performed both with and without the inclusion of explosion gas loading to explore the respective contributions of blasting stress waves and explosion gases to crater formation. The results show that the blasting crater dimensions simulated with the dynamic-static sequential loading model align closely with field test results, accurately capturing the formation and evolution of fractures in the blasting zone and the ejection behavior of fragmented rock. The high loading rate of blasting stress waves is the primary cause of ring-shaped microfractures in the near-field region of the explosion source, which can also induce reflective tensile damage, forming “slice drop” failure at free surfaces. Explosion gases, on the other hand, are the main drivers of radially extensive fractures in the far-field region of the explosion source and propel fragmented rock outward at a high velocity. Explosion gases exhibit not only quasi-static effects but also dynamic effects, extending the duration of blasting vibrations and amplifying the peak vibration velocity. The development of fractures during crater formation can be broadly categorized into three stages: stress wave-induced fracturing, explosion gas-induced fracturing, and deformation energy release-induced fracturing.
, Available online , doi: 10.11883/bzycj-2024-0191
Abstract:
For the estimation of blast loading in complex structures, traditional numerical simulation methods were computationally intensive whereas rapid estimation methods based on neural networks can only provide estimates at local points without providing confidence intervals for the predicted results. To achieve fast and reliable estimation of the blast loading in complex structures, Bayesian theory was combined with deep learning to develop a Bayesian deep learning approach for rapid estimation of blast loading in complex structures. The approach initially utilized open-source numerical simulation software to generate a dataset of blast loading in complex structures, encompassing a wide range of parameters such as explosion equivalents, locations, and velocities. During this process, mesh sizes that balanced computational accuracy and speed were determined through mesh sensitivity analysis and the verification of the numerical simulation accuracy. Then, the deep learning model was extended into a Bayesian deep learning model based on Bayesian theory. By introducing probability distributions over the weights of the neural network, the model parameters were treated as random variables. Variational Bayesian inference was then employed to efficiently train the model, ensuring the accuracy of rapid blast loading estimation while also equipping the model with the ability to quantify uncertainty. Finally, metrics such as mean absolute percentage error (MAPE), normalized mean prediction interval width (NMPIW) and prediction interval coverage probability (PICP) were adopted to quantitatively assess the model's estimated accuracy and the precision of the uncertainty quantification. Additionally, an error decomposition of the estimation results was conducted to analyze model’s performance based on target parameters and scaled distance. The results indicate that the proposed method achieved an estimation error of 12.2% on the test set, with a confidence interval covering over 81.6% of true values, and less than 20 milliseconds of the estimation time for a single sample point. This method provides a novel approach for fast and accurate estimation of blast loading in complex structures with sufficient confidence for the estimation results.
For the estimation of blast loading in complex structures, traditional numerical simulation methods were computationally intensive whereas rapid estimation methods based on neural networks can only provide estimates at local points without providing confidence intervals for the predicted results. To achieve fast and reliable estimation of the blast loading in complex structures, Bayesian theory was combined with deep learning to develop a Bayesian deep learning approach for rapid estimation of blast loading in complex structures. The approach initially utilized open-source numerical simulation software to generate a dataset of blast loading in complex structures, encompassing a wide range of parameters such as explosion equivalents, locations, and velocities. During this process, mesh sizes that balanced computational accuracy and speed were determined through mesh sensitivity analysis and the verification of the numerical simulation accuracy. Then, the deep learning model was extended into a Bayesian deep learning model based on Bayesian theory. By introducing probability distributions over the weights of the neural network, the model parameters were treated as random variables. Variational Bayesian inference was then employed to efficiently train the model, ensuring the accuracy of rapid blast loading estimation while also equipping the model with the ability to quantify uncertainty. Finally, metrics such as mean absolute percentage error (MAPE), normalized mean prediction interval width (NMPIW) and prediction interval coverage probability (PICP) were adopted to quantitatively assess the model's estimated accuracy and the precision of the uncertainty quantification. Additionally, an error decomposition of the estimation results was conducted to analyze model’s performance based on target parameters and scaled distance. The results indicate that the proposed method achieved an estimation error of 12.2% on the test set, with a confidence interval covering over 81.6% of true values, and less than 20 milliseconds of the estimation time for a single sample point. This method provides a novel approach for fast and accurate estimation of blast loading in complex structures with sufficient confidence for the estimation results.
, Available online , doi: 10.11883/bzycj-2024-0203
Abstract:
The equation of state for the detonation products of explosives is one of the foundations in explosion physics. JWL equation of state has been widely applied to study the properties of various explosives. In order to obtain the equation of state of the detonation products, an underwater explosion method was used to study JWL equation of state for the detonation of RDX. It considered the explosion bubble expansion process based on the conservation of energy including Es0 (initial shock wave energy), Ept (potential energy of water), Ec (kinetic energy of water) and Er (energy loss by bubble expansion), which are related to the underwater explosion bubble radius (R-t) and shock wave front (Rs-t) measured in the underwater explosion experiments as functions of time. Based on the experimental results and using the same method to process the experimental data in cylinder experiment, the time functions of explosion bubble expansion radius and variation of shock wave front position were fitted and the parameters of the JWL equation of state for RDX detonation products were obtained. In order to analyze the accuracy of the parameters of the JWL equation of state obtained by the underwater explosion method, the time history of the underwater explosions bubble pulsating pressure wave was calculated using the bubble dynamics equation. It shows that the calculation results agree well with the bubble expansion radius and bubble pulsation period determined using the underwater explosion experiments in a pool. The calculated bubble radius obtained by the proposed measurement method has a smaller deviation from that obtained by the cylinder experimental value, especially in the low-pressure stage compare with the JWL state parameters obtained from cylinder method. This method provides a testing approach for the equation of state of detonation products with low cost, reduced size limitations and a wide pressure range.
The equation of state for the detonation products of explosives is one of the foundations in explosion physics. JWL equation of state has been widely applied to study the properties of various explosives. In order to obtain the equation of state of the detonation products, an underwater explosion method was used to study JWL equation of state for the detonation of RDX. It considered the explosion bubble expansion process based on the conservation of energy including Es0 (initial shock wave energy), Ept (potential energy of water), Ec (kinetic energy of water) and Er (energy loss by bubble expansion), which are related to the underwater explosion bubble radius (R-t) and shock wave front (Rs-t) measured in the underwater explosion experiments as functions of time. Based on the experimental results and using the same method to process the experimental data in cylinder experiment, the time functions of explosion bubble expansion radius and variation of shock wave front position were fitted and the parameters of the JWL equation of state for RDX detonation products were obtained. In order to analyze the accuracy of the parameters of the JWL equation of state obtained by the underwater explosion method, the time history of the underwater explosions bubble pulsating pressure wave was calculated using the bubble dynamics equation. It shows that the calculation results agree well with the bubble expansion radius and bubble pulsation period determined using the underwater explosion experiments in a pool. The calculated bubble radius obtained by the proposed measurement method has a smaller deviation from that obtained by the cylinder experimental value, especially in the low-pressure stage compare with the JWL state parameters obtained from cylinder method. This method provides a testing approach for the equation of state of detonation products with low cost, reduced size limitations and a wide pressure range.
, Available online , doi: 10.11883/bzycj-2024-0239
Abstract:
In order to explore the underwater anti-explosion protection effect of steel fiber reinforced cellular concrete materials, the damage process of reinforced concrete slabs under underwater contact explosion was reproduced by the coupling method of smoothed particle hydrodynamics and finite element method (SPH-FEM). The validity of the simulation method was verified by comparing with the experimental results. On this basis, a three-dimensional refined simulation model of water-explosive-protective layer-reinforced concrete slab was established by the SPH-FEM coupling method. The damage evolution process, failure mode and failure mechanism of protective layer of steel fiber reinforced cellular concrete (SAP10S5, SAP10S10, SAP10S15 and SAP10S20) with different fiber ratios and explosive mass were studied, and the prediction curve of damage level of reinforced concrete slabs was constructed. The results show that the numerical simulation results are in good agreement with the experimental results, which verifies the effectiveness of the simulation method. Under the underwater contact explosion, the addition of protective layer of steel fiber reinforced cellular concrete can effectively reduce the damage degree of protected reinforced concrete (RC) slab, and its influence on the damage degree of RC slab decreases first and then increases with the increase of steel fiber volume fraction in the protective layer. Among them, the anti-explosion protection effect of protective layer of SAP10S15 ratio is the best. When the amount of explosive increases within a certain range, the protective layer of SAP10S15 ratio can still maintain a high proportion of energy consumption and effectively reduce the damage degree of the RC plate. When the amount of explosive is 0.25 kg, the damage index of RC slabs strengthened with protective layer of SAP10S15 has the most obvious attenuation compared with the unprotected scheme, which is 42.5%, and the damage level is reduced from serious damage to moderate damage. The prediction curve of constructed damage level can directly evaluate the influence of steel fiber volume fraction/explosive amount on the damage degree of RC panel. The above research results can provide reference for the anti-explosion protection design of wading concrete structures.
In order to explore the underwater anti-explosion protection effect of steel fiber reinforced cellular concrete materials, the damage process of reinforced concrete slabs under underwater contact explosion was reproduced by the coupling method of smoothed particle hydrodynamics and finite element method (SPH-FEM). The validity of the simulation method was verified by comparing with the experimental results. On this basis, a three-dimensional refined simulation model of water-explosive-protective layer-reinforced concrete slab was established by the SPH-FEM coupling method. The damage evolution process, failure mode and failure mechanism of protective layer of steel fiber reinforced cellular concrete (SAP10S5, SAP10S10, SAP10S15 and SAP10S20) with different fiber ratios and explosive mass were studied, and the prediction curve of damage level of reinforced concrete slabs was constructed. The results show that the numerical simulation results are in good agreement with the experimental results, which verifies the effectiveness of the simulation method. Under the underwater contact explosion, the addition of protective layer of steel fiber reinforced cellular concrete can effectively reduce the damage degree of protected reinforced concrete (RC) slab, and its influence on the damage degree of RC slab decreases first and then increases with the increase of steel fiber volume fraction in the protective layer. Among them, the anti-explosion protection effect of protective layer of SAP10S15 ratio is the best. When the amount of explosive increases within a certain range, the protective layer of SAP10S15 ratio can still maintain a high proportion of energy consumption and effectively reduce the damage degree of the RC plate. When the amount of explosive is 0.25 kg, the damage index of RC slabs strengthened with protective layer of SAP10S15 has the most obvious attenuation compared with the unprotected scheme, which is 42.5%, and the damage level is reduced from serious damage to moderate damage. The prediction curve of constructed damage level can directly evaluate the influence of steel fiber volume fraction/explosive amount on the damage degree of RC panel. The above research results can provide reference for the anti-explosion protection design of wading concrete structures.
, Available online , doi: 10.11883/bzycj-2024-0279
Abstract:
Prefabricated concrete bursting layer has a very important application prospect in the field of protective engineering attributed to its technical advantages including high construction efficiency and construction quality. However, compared with the monolithic cast-in-situ concrete bursting layer, the impact resistance of the prefabricated concrete bursting layer may be significantly reduced because of the interfaces between the prefabricated blocks and the cast-in-situ part. Therefore, it is important for engineers to reasonably design the prefabricated concrete bursting layer to make its penetration resistance comparable to the monolithic one. To this end, a kind of prefabricated bursting layer connected by wet joints and rebars was proposed in our previous study. In order to apply the prefabricated bursting layer in protective engineering, a series of numerical models were developed to further study its penetration resistance. Firstly, based on the Kong-Fang model and smoothed particle Galerkin (SPG) method, the numerical models were developed and validated against the experimental data of projectile penetrating monolithic and prefabricated targets. Then, the validated numerical models were further used to investigate the influences of prefabricated block size, wet joint width and anchorage length, spacing and diameter of rebars on the penetration resistance of prefabricated targets. Numerical results indicate that increasing the width of wet joints, reducing the spacing between rebars, and extending the anchorage length of rebars can significantly enhance the penetration resistance of prefabricated targets. After clarifying the influences of these parameters, an engineering design method for a prefabricated concrete bursting layer was proposed. Finally, based on this method, two prefabricated high performance concrete targets subjected to two typical types of warhead penetration were designed. Numerical results show that the penetration resistances of two prefabricated targets were comparable to monolithic targets. The proposed engineering design method can provide a reference for engineering applications of prefabricated concrete bursting layers connected by the wet joints and rebars.
Prefabricated concrete bursting layer has a very important application prospect in the field of protective engineering attributed to its technical advantages including high construction efficiency and construction quality. However, compared with the monolithic cast-in-situ concrete bursting layer, the impact resistance of the prefabricated concrete bursting layer may be significantly reduced because of the interfaces between the prefabricated blocks and the cast-in-situ part. Therefore, it is important for engineers to reasonably design the prefabricated concrete bursting layer to make its penetration resistance comparable to the monolithic one. To this end, a kind of prefabricated bursting layer connected by wet joints and rebars was proposed in our previous study. In order to apply the prefabricated bursting layer in protective engineering, a series of numerical models were developed to further study its penetration resistance. Firstly, based on the Kong-Fang model and smoothed particle Galerkin (SPG) method, the numerical models were developed and validated against the experimental data of projectile penetrating monolithic and prefabricated targets. Then, the validated numerical models were further used to investigate the influences of prefabricated block size, wet joint width and anchorage length, spacing and diameter of rebars on the penetration resistance of prefabricated targets. Numerical results indicate that increasing the width of wet joints, reducing the spacing between rebars, and extending the anchorage length of rebars can significantly enhance the penetration resistance of prefabricated targets. After clarifying the influences of these parameters, an engineering design method for a prefabricated concrete bursting layer was proposed. Finally, based on this method, two prefabricated high performance concrete targets subjected to two typical types of warhead penetration were designed. Numerical results show that the penetration resistances of two prefabricated targets were comparable to monolithic targets. The proposed engineering design method can provide a reference for engineering applications of prefabricated concrete bursting layers connected by the wet joints and rebars.
, Available online , doi: 10.11883/bzycj-2024-0207
Abstract:
To investigate the dynamic mechanical characterization of non-pure and non-intact ice materials under impact loads, a modified split Hopkinson pressure bar (SHPB) was used. Rapid loading, rod end cooling and waveform shaping techniques were used to ensure the stability of the ice material and achieve dynamic stress balance during loading. The impact mechanical properties of complete ice (pure water, containing 2.5%, 3.5%, 4.5% salt, containing 2.0%, 4.5%, 8.5% coconut) and spliced ice (splicing interface inclination 30°, 60°) at freezing temperature of −10 ℃ were studied. The strain rate ranges from 150~250 s−1. The failure process was recorded by using the high-speed camera triggered simultaneously with the pressure rod. The correlation between the stress and strain of the sample, along with the failure process, was determined by analyzing the time history curve of sample. The failure mode of the spliced ice sample was analyzed by combining the Mohr-Coulomb strength criterion. The results show that the pure water ice exhibits the highest compressive strength, followed by the ice with coconut shreds, and both of them show a positive strain rate effect. However, the compressive strength of the ice with salt addition decreases significantly due to its loose structure and the strain rate effect is not obvious. The dynamic compressive strength of ice samples added with coconut fiber increases firstly and then decreases with the increase of coconut fiber content. Ice samples with high coconut fiber content are prone to "double peak" phenomenon due to the binding effect of coconut fiber on broken ice with small particle size. The splicing plane affects the crack growth, resulting in lower compressive strength than the intact ice sample, and affects the failure mode as well. The ice with small interface inclination is mainly damaged by interface slip, while the ice with large interface inclination is mainly damaged by whole ice, which is similar to the intact ice. The research results provide theoretical basis and method reference for the dynamic mechanical properties of non-pure and non-intact ice materials under impact loads.
To investigate the dynamic mechanical characterization of non-pure and non-intact ice materials under impact loads, a modified split Hopkinson pressure bar (SHPB) was used. Rapid loading, rod end cooling and waveform shaping techniques were used to ensure the stability of the ice material and achieve dynamic stress balance during loading. The impact mechanical properties of complete ice (pure water, containing 2.5%, 3.5%, 4.5% salt, containing 2.0%, 4.5%, 8.5% coconut) and spliced ice (splicing interface inclination 30°, 60°) at freezing temperature of −10 ℃ were studied. The strain rate ranges from 150~250 s−1. The failure process was recorded by using the high-speed camera triggered simultaneously with the pressure rod. The correlation between the stress and strain of the sample, along with the failure process, was determined by analyzing the time history curve of sample. The failure mode of the spliced ice sample was analyzed by combining the Mohr-Coulomb strength criterion. The results show that the pure water ice exhibits the highest compressive strength, followed by the ice with coconut shreds, and both of them show a positive strain rate effect. However, the compressive strength of the ice with salt addition decreases significantly due to its loose structure and the strain rate effect is not obvious. The dynamic compressive strength of ice samples added with coconut fiber increases firstly and then decreases with the increase of coconut fiber content. Ice samples with high coconut fiber content are prone to "double peak" phenomenon due to the binding effect of coconut fiber on broken ice with small particle size. The splicing plane affects the crack growth, resulting in lower compressive strength than the intact ice sample, and affects the failure mode as well. The ice with small interface inclination is mainly damaged by interface slip, while the ice with large interface inclination is mainly damaged by whole ice, which is similar to the intact ice. The research results provide theoretical basis and method reference for the dynamic mechanical properties of non-pure and non-intact ice materials under impact loads.
, Available online , doi: 10.11883/bzycj-2024-0099
Abstract:
Artificial intelligence/machine learning methods can discover hidden physical patterns in data. By constructing an end-to-end surrogate model between state parameters and dynamic results, many complex engineering problems such as strong coupling, nonlinearity, and multiphysics can be efficiently solved. In the field of highly nonlinear explosion and shock dynamics, a classic detonation driving problem was chosen as the research object. Using numerical simulation results as training data for machine learning surrogate models, and combining forward simulation and reverse design organically. Based on deep neural network technology, an end-to-end surrogate model was constructed between feature position velocity profiles, material dynamic deformation, and engineering factors. And the calculation accuracy of the surrogate model was provided, verifying the ability to invert engineering factors from velocity profiles. The research results indicate that the end-to-end surrogate model has high predictive ability, with relative errors of less than 1% in both velocity profile prediction and engineering factor estimation. It can be applied to the rapid design, high-precision prediction, and agile iteration of highly nonlinear explosion and impact dynamics problems.
Artificial intelligence/machine learning methods can discover hidden physical patterns in data. By constructing an end-to-end surrogate model between state parameters and dynamic results, many complex engineering problems such as strong coupling, nonlinearity, and multiphysics can be efficiently solved. In the field of highly nonlinear explosion and shock dynamics, a classic detonation driving problem was chosen as the research object. Using numerical simulation results as training data for machine learning surrogate models, and combining forward simulation and reverse design organically. Based on deep neural network technology, an end-to-end surrogate model was constructed between feature position velocity profiles, material dynamic deformation, and engineering factors. And the calculation accuracy of the surrogate model was provided, verifying the ability to invert engineering factors from velocity profiles. The research results indicate that the end-to-end surrogate model has high predictive ability, with relative errors of less than 1% in both velocity profile prediction and engineering factor estimation. It can be applied to the rapid design, high-precision prediction, and agile iteration of highly nonlinear explosion and impact dynamics problems.
, Available online , doi: 10.11883/bzycj-2024-0254
Abstract:
To address the issues of over-excavation at the tunnel arch foot due to the difficulty of forming the perimeter hole blasting and under-excavation at the tunnel face bottom, the damage characteristics of surrounding rock caused by perimeter hole blasting at the arch foot of a horseshoe-shaped tunnel were studied through a combination of theoretical calculations and numerical simulations. On the theoretical level, an in-depth analysis of the stress distribution and crack radius in the arch foot area was conducted based on the principles of blasting mechanics, and the theoretical charge length for the perimeter holes at the arch foot was derived. Building on this, a 3D numerical model of the perimeter holes at the arch foot was established through numerical simulation. During the modeling process, the damage evolution in the surrounding rock during blasting was simulated by introducing an appropriate damage model, and post-blast damage cloud maps were generated. By comparing the damage cloud maps under different conditions, the relationship between blasting effectiveness and parameters such as free surface shape, charge amount, and void deflection angle was analyzed, further revealing the mechanisms by which these parameters influence the blasting formation results, which were validated through field experiments. The research results indicate that the shape of the free surface significantly impacts the extent of surrounding rock damage and the energy utilization efficiency of explosives. A concave free surface results in a smaller damage range compared to a flat free surface, with greater rock confinement, making it difficult for the explosives to effectively fracture the surrounding rock, leading to an energy utilization rate of only 78%. The blasting effectiveness shows a trend of first increasing and then decreasing with the increase in charge amount, with the optimal blasting effectiveness achieved when the linear charge density of the perimeter holes at the arch foot is 0.624. Additionally, by setting voids and adjusting the void deflection angle, the blasting effectiveness of the perimeter holes at the arch foot can be improved. With the optimized blasting parameters, the maximum linear over-excavation at the arch foot was reduced by 53.1%, resulting in a smooth tunnel contour. The research outcomes are engineeringly feasible and provide valuable insights for similar projects.
To address the issues of over-excavation at the tunnel arch foot due to the difficulty of forming the perimeter hole blasting and under-excavation at the tunnel face bottom, the damage characteristics of surrounding rock caused by perimeter hole blasting at the arch foot of a horseshoe-shaped tunnel were studied through a combination of theoretical calculations and numerical simulations. On the theoretical level, an in-depth analysis of the stress distribution and crack radius in the arch foot area was conducted based on the principles of blasting mechanics, and the theoretical charge length for the perimeter holes at the arch foot was derived. Building on this, a 3D numerical model of the perimeter holes at the arch foot was established through numerical simulation. During the modeling process, the damage evolution in the surrounding rock during blasting was simulated by introducing an appropriate damage model, and post-blast damage cloud maps were generated. By comparing the damage cloud maps under different conditions, the relationship between blasting effectiveness and parameters such as free surface shape, charge amount, and void deflection angle was analyzed, further revealing the mechanisms by which these parameters influence the blasting formation results, which were validated through field experiments. The research results indicate that the shape of the free surface significantly impacts the extent of surrounding rock damage and the energy utilization efficiency of explosives. A concave free surface results in a smaller damage range compared to a flat free surface, with greater rock confinement, making it difficult for the explosives to effectively fracture the surrounding rock, leading to an energy utilization rate of only 78%. The blasting effectiveness shows a trend of first increasing and then decreasing with the increase in charge amount, with the optimal blasting effectiveness achieved when the linear charge density of the perimeter holes at the arch foot is 0.624. Additionally, by setting voids and adjusting the void deflection angle, the blasting effectiveness of the perimeter holes at the arch foot can be improved. With the optimized blasting parameters, the maximum linear over-excavation at the arch foot was reduced by 53.1%, resulting in a smooth tunnel contour. The research outcomes are engineeringly feasible and provide valuable insights for similar projects.
, Available online , doi: 10.11883/bzycj-2024-0121
Abstract:
The large-scale explosive dispersal and the unconfined detonation of particle-spray-air ternary mixtures are closely related to industrial accidents and military applications. However, most of the existing research focuses on the small-scale experiment in the laboratory, with large-scale explosive dispersal experiments being relatively scarce. The initiation state of the aerosol cloud determines the blast power, and the device structure and specific explosive charge are the main factors affecting the cloud morphology. To study the damaging effect of aerosol, the large-scale dispersed experiment of 125 kg fuel was carried out. The process of aerosol development was observed by high-speed video recording. Variation characteristics of FAE cloud with different canisters and the specific central explosive were studied. The aerosol diameter and height were used to describing the aerosol shape, then they were analyzed under different initial experiment conditions. Three types of canisters were utilized, namely the basic canister, the compound canister, and the strengthen canister, with the primary difference being their radial restraint mechanisms. The specific central explosive was adopted the T-shaped charge. The results show that the aerosol formation is reliable through the replication experiments. Because of its strong radial restraint, the compound canister has the advantage in the aerosol diameters. The aerosol diameters of compound canister can reach 25.5 m, compared to strong canister coverage area increased by 13%. Therefore, the compound canister with the specific central explosive of 0.8% has the best aerosol performance for 125 kg fuel. On this basis, characteristics of the aerosol were further analyzed. The optimal secondary detonation delay time is 240 ms. The calculating aerosol concentration before burst is 64 g/m3 and the chemical equivalent ratio of fuel to oxygen in the air is 0.54.
The large-scale explosive dispersal and the unconfined detonation of particle-spray-air ternary mixtures are closely related to industrial accidents and military applications. However, most of the existing research focuses on the small-scale experiment in the laboratory, with large-scale explosive dispersal experiments being relatively scarce. The initiation state of the aerosol cloud determines the blast power, and the device structure and specific explosive charge are the main factors affecting the cloud morphology. To study the damaging effect of aerosol, the large-scale dispersed experiment of 125 kg fuel was carried out. The process of aerosol development was observed by high-speed video recording. Variation characteristics of FAE cloud with different canisters and the specific central explosive were studied. The aerosol diameter and height were used to describing the aerosol shape, then they were analyzed under different initial experiment conditions. Three types of canisters were utilized, namely the basic canister, the compound canister, and the strengthen canister, with the primary difference being their radial restraint mechanisms. The specific central explosive was adopted the T-shaped charge. The results show that the aerosol formation is reliable through the replication experiments. Because of its strong radial restraint, the compound canister has the advantage in the aerosol diameters. The aerosol diameters of compound canister can reach 25.5 m, compared to strong canister coverage area increased by 13%. Therefore, the compound canister with the specific central explosive of 0.8% has the best aerosol performance for 125 kg fuel. On this basis, characteristics of the aerosol were further analyzed. The optimal secondary detonation delay time is 240 ms. The calculating aerosol concentration before burst is 64 g/m3 and the chemical equivalent ratio of fuel to oxygen in the air is 0.54.
, Available online , doi: 10.11883/bzycj-2024-0244
Abstract:
Accurately evaluating the continuous effect of penetration and moving charge explosion of earth penetrating weapons is the premise of reliable design of shield on the protective structure. Firstly, a three-stage integrated projectile penetration and moving charge explosion finite element analysis method was proposed based on the technologies of volume filling of explosive and the two-step coupling in penetration and explosion processes. By conducting the numerical simulations of the existing tests of moving charge explosion, penetration and static charge explosion of normal strength concrete (NSC) and ultra-high performance concrete (UHPC) targets, the accuracy of the proposed method in describing the propagation of explosive waves, peak stress, cracking behavior and damage evolution of target under the penetration and explosion was fully verified. Besides, for the scenario of an NSC target against a 105 mm-caliber scaled projectile, the differences of target damage predicted by the proposed finite element analysis method and traditional penetration and static charge explosion method were compared. Meanwhile, the superimposed effect of the penetration and explosion stress field and the influence of shell constraint and fracture fragment were analyzed. Based on the damage characteristics of targets at different detonation time instants of explosive, the most unfavorable detonation time instant of the warhead was determined. Finally, numerical simulations were conducted for the scenarios of three prototype warheads: SDB, WDU-43/B and BLU-109/B. The destructive depths of NSC and UHPC shields subjected to the penetration and moving charge explosion loadings are 1.33, 2.70, 2.35 m and 0.79, 1.76, 1.70 m, respectively. The corresponding scabbing and perforation limits of shields were further given. The results show that the destructive depths, scabbing limits and perforation limits calculated by the finite element analysis method with considering integrated penetration and moving charge explosion are about 5%–30% higher than those calculated by the traditional penetration and static charge explosion method.
Accurately evaluating the continuous effect of penetration and moving charge explosion of earth penetrating weapons is the premise of reliable design of shield on the protective structure. Firstly, a three-stage integrated projectile penetration and moving charge explosion finite element analysis method was proposed based on the technologies of volume filling of explosive and the two-step coupling in penetration and explosion processes. By conducting the numerical simulations of the existing tests of moving charge explosion, penetration and static charge explosion of normal strength concrete (NSC) and ultra-high performance concrete (UHPC) targets, the accuracy of the proposed method in describing the propagation of explosive waves, peak stress, cracking behavior and damage evolution of target under the penetration and explosion was fully verified. Besides, for the scenario of an NSC target against a 105 mm-caliber scaled projectile, the differences of target damage predicted by the proposed finite element analysis method and traditional penetration and static charge explosion method were compared. Meanwhile, the superimposed effect of the penetration and explosion stress field and the influence of shell constraint and fracture fragment were analyzed. Based on the damage characteristics of targets at different detonation time instants of explosive, the most unfavorable detonation time instant of the warhead was determined. Finally, numerical simulations were conducted for the scenarios of three prototype warheads: SDB, WDU-43/B and BLU-109/B. The destructive depths of NSC and UHPC shields subjected to the penetration and moving charge explosion loadings are 1.33, 2.70, 2.35 m and 0.79, 1.76, 1.70 m, respectively. The corresponding scabbing and perforation limits of shields were further given. The results show that the destructive depths, scabbing limits and perforation limits calculated by the finite element analysis method with considering integrated penetration and moving charge explosion are about 5%–30% higher than those calculated by the traditional penetration and static charge explosion method.
, Available online , doi: 10.11883/bzycj-2024-0229
Abstract:
To investigate the influence of the density of crushed ice region on the cavity evolution of a structure, an oblique water-entry experiment of the structure was conducted by high-speed photography technology under different crushed ice cover densities. Moreover, by comparing the water-entry process of the oblique structure in varying densities of crushed ice cover, the influence of crushed ice cover density on cavity evolution during the oblique water-entry process of the structure was obtained. Results indicate that during the cavity expansion, the presence of crushed ice reduces the cavity diameter by impeding the outward expansion of the fluid near the free surface, compared with the ice-free environment. When the cavity closes, crushed ice also impedes the inward contraction of the free surface fluid and prolongs the cavity expansion time. The augmentation in the total volume of air within the cavity results in a decrement of the pressure differential between the inside and outside of the cavity, ultimately leading to a retardation in the cavity closure time. In conditions of lower crushed ice densities, jets point to the interior of the cavity when the cavity collapses. As the coverage density of crushed ice gradually increases, the impedance exerted by the crushed ice on the inward contraction of fluid at the free surface progressively intensifies. This enhanced obstruction from the crushed ice further prolongs the cavity closure time and concurrently augments its length and maximum diameter. Besides, under conditions of higher crushed ice cover densities, the cavity wall is wrinkled by the irregular impact of the fluid. As the submerged depth of the structure increases, the cavity undergoes a deep necking under the influence of ambient pressure. As the coverage density of crushed ice gradually increases, the velocity of the underwater motion of the structure shows a trend of faster decay compared with those in ice-free environments.
To investigate the influence of the density of crushed ice region on the cavity evolution of a structure, an oblique water-entry experiment of the structure was conducted by high-speed photography technology under different crushed ice cover densities. Moreover, by comparing the water-entry process of the oblique structure in varying densities of crushed ice cover, the influence of crushed ice cover density on cavity evolution during the oblique water-entry process of the structure was obtained. Results indicate that during the cavity expansion, the presence of crushed ice reduces the cavity diameter by impeding the outward expansion of the fluid near the free surface, compared with the ice-free environment. When the cavity closes, crushed ice also impedes the inward contraction of the free surface fluid and prolongs the cavity expansion time. The augmentation in the total volume of air within the cavity results in a decrement of the pressure differential between the inside and outside of the cavity, ultimately leading to a retardation in the cavity closure time. In conditions of lower crushed ice densities, jets point to the interior of the cavity when the cavity collapses. As the coverage density of crushed ice gradually increases, the impedance exerted by the crushed ice on the inward contraction of fluid at the free surface progressively intensifies. This enhanced obstruction from the crushed ice further prolongs the cavity closure time and concurrently augments its length and maximum diameter. Besides, under conditions of higher crushed ice cover densities, the cavity wall is wrinkled by the irregular impact of the fluid. As the submerged depth of the structure increases, the cavity undergoes a deep necking under the influence of ambient pressure. As the coverage density of crushed ice gradually increases, the velocity of the underwater motion of the structure shows a trend of faster decay compared with those in ice-free environments.
