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, Available online , doi: 10.11883/bzycj-2024-0298
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In military operations, industrial accidents and other explosive events, head injuries caused by blast shock waves have become one of the main injury forms of injury, but the injury mechanism and damage threshold have not been clarified yet. In this paper, numerical simulation is used to study the dynamic response process of the head under explosion load, and the effects of TNT charge, air and water media on the deformation, pressure and acceleration of the cranium and brain are analyzed. First, the air-head fluid-structure interaction model is established using Euler-Lagrangian coupling method. Based on the validation of its effectiveness, the dynamic response process of the head was analyzed in terms of pressure, acceleration and frequency of the prefrontal cranium and brain tissue. By setting the initial conditions and boundary conditions, the effects of frontal and the behind shock loadings of the blast wave on the head were simulated. It has been found that the head tissue vibrates at high frequencies, up to 7 kHz, when the blast wave strikes the head directly. The acceleration on the prefrontal cranium and brain tissue had a large value initially and become small in the late stage, while the intracranial pressure varied in a cyclical manner. In the underwater environment, there were high-frequency periodic overpressure fluctuations in the brain tissues of frontal, parietal and temporal lobes, in which peak overpressure of 3.64 MPa can be generated in the prefrontal cranium, which is well above the threshold of 235 kPa for severe brain injury. In water, brain tissue is subjected to 5 times the peak pressure, a 5 fold increase in acceleration and a 2 fold increase in frequency compared to those in air. The results of this research provide a new perspective for understanding the mechanism of damage to the human brain caused by blast shock waves, and an reference for the development of future protective measures.
In military operations, industrial accidents and other explosive events, head injuries caused by blast shock waves have become one of the main injury forms of injury, but the injury mechanism and damage threshold have not been clarified yet. In this paper, numerical simulation is used to study the dynamic response process of the head under explosion load, and the effects of TNT charge, air and water media on the deformation, pressure and acceleration of the cranium and brain are analyzed. First, the air-head fluid-structure interaction model is established using Euler-Lagrangian coupling method. Based on the validation of its effectiveness, the dynamic response process of the head was analyzed in terms of pressure, acceleration and frequency of the prefrontal cranium and brain tissue. By setting the initial conditions and boundary conditions, the effects of frontal and the behind shock loadings of the blast wave on the head were simulated. It has been found that the head tissue vibrates at high frequencies, up to 7 kHz, when the blast wave strikes the head directly. The acceleration on the prefrontal cranium and brain tissue had a large value initially and become small in the late stage, while the intracranial pressure varied in a cyclical manner. In the underwater environment, there were high-frequency periodic overpressure fluctuations in the brain tissues of frontal, parietal and temporal lobes, in which peak overpressure of 3.64 MPa can be generated in the prefrontal cranium, which is well above the threshold of 235 kPa for severe brain injury. In water, brain tissue is subjected to 5 times the peak pressure, a 5 fold increase in acceleration and a 2 fold increase in frequency compared to those in air. The results of this research provide a new perspective for understanding the mechanism of damage to the human brain caused by blast shock waves, and an reference for the development of future protective measures.
, Available online , doi: 10.11883/bzycj-2024-0485
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To accurately predict the dynamic tensile fracture in concrete materials subjected to impact and blast loadings, this study first establishes a modified Monaghan artificial bulk viscosity computation method within the framework of a non-ordinary state-based peridynamics (NOSB-PD) theory to eliminate numerical oscillations. Subsequently, the corrected strain-rate computation method, previously developed, is integrated into the Kong-Fang concrete material model, which was proposed earlier by the research group to calculate accurately the strain-rate effect during sudden changes. Based on the two methods above, numerical simulations of elastic wave propagation in a one-dimensional rod are conducted, and the results demonstrate that the additional inclusion of the modified Monaghan artificial bulk viscosity force vector state into the original force vector state can effectively suppress the non-physical numerical oscillations caused by the deformation gradient approximation. The superiority of the modified Monaghan artificial bulk viscosity is validated through comparative analysis with the original Monaghan artificial bulk viscosity. Furthermore, the influence of the modified Monaghan artificial bulk viscosity parameters is investigated, and recommended values for these parameters are provided. Finally, the aforementioned model is used to numerically simulate the spall test in concrete specimens, where the effects of including or excluding the modified Monaghan artificial bulk viscosity and different strain-rate computation methods on the prediction results of dynamic tensile fracture are compared and analyzed. The numerical simulation results demonstrate that accurately predicting the dynamic tensile fracture in concrete materials requires simultaneous consideration of the modified Monaghan artificial bulk viscosity and corrected strain-rate computation. The established non-ordinary state-based peridynamics model that accounts for both the modified Monaghan artificial bulk viscosity and corrected strain-rate computation demonstrates strong capabilities in predicting crack locations and quantities based on both qualitative and quantitative analysis metrics. This work provides new insights into the numerical simulation of dynamic tensile fracture in concrete materials under impact and blast loadings.
To accurately predict the dynamic tensile fracture in concrete materials subjected to impact and blast loadings, this study first establishes a modified Monaghan artificial bulk viscosity computation method within the framework of a non-ordinary state-based peridynamics (NOSB-PD) theory to eliminate numerical oscillations. Subsequently, the corrected strain-rate computation method, previously developed, is integrated into the Kong-Fang concrete material model, which was proposed earlier by the research group to calculate accurately the strain-rate effect during sudden changes. Based on the two methods above, numerical simulations of elastic wave propagation in a one-dimensional rod are conducted, and the results demonstrate that the additional inclusion of the modified Monaghan artificial bulk viscosity force vector state into the original force vector state can effectively suppress the non-physical numerical oscillations caused by the deformation gradient approximation. The superiority of the modified Monaghan artificial bulk viscosity is validated through comparative analysis with the original Monaghan artificial bulk viscosity. Furthermore, the influence of the modified Monaghan artificial bulk viscosity parameters is investigated, and recommended values for these parameters are provided. Finally, the aforementioned model is used to numerically simulate the spall test in concrete specimens, where the effects of including or excluding the modified Monaghan artificial bulk viscosity and different strain-rate computation methods on the prediction results of dynamic tensile fracture are compared and analyzed. The numerical simulation results demonstrate that accurately predicting the dynamic tensile fracture in concrete materials requires simultaneous consideration of the modified Monaghan artificial bulk viscosity and corrected strain-rate computation. The established non-ordinary state-based peridynamics model that accounts for both the modified Monaghan artificial bulk viscosity and corrected strain-rate computation demonstrates strong capabilities in predicting crack locations and quantities based on both qualitative and quantitative analysis metrics. This work provides new insights into the numerical simulation of dynamic tensile fracture in concrete materials under impact and blast loadings.
, Available online , doi: 10.11883/bzycj-2024-0385
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The crack propagation behavior of brittle materials, such as rock, is often challenging to capture under explosive loading conditions. To address this issue, model experiments were conducted based on the theory of explosive damage, utilizing transparent polymethyl methacrylate as a surrogate material to simulate the fracture response of brittle materials. High-speed photography and computed tomography scanning were employed to investigate the dynamic fracture process and three-dimensional crack evolution under blast loading. In addition, 3D scanning technology was used to reconstruct the morphology of cracks and characterize the fracture surface features. The results indicate that under the sustained action of multi-stage explosive energy, cracks undergo repeated initiation and propagation. Initial cracks induced by shock waves exhibit high density and a “fish scale” pattern, primarily concentrated around the blast hole. In contrast, secondary cracks driven by detonation gases have a lower density and extend outward in “ear-shaped” or “dagger-shaped” forms. As the distance from the explosion center increases, the crack surface morphology transitions from rugged to microwave-like textures, with improved flatness. Specifically, the elevation variance of the fracture surface decreases from 0.796 to 0.586, while the maximum height reduces from 3.2 mm to 2.8 mm, representing a 12.5% reduction. Moreover, the failure mode of the material shifts from compressive-shear to tensile failure with increasing distance from the explosion center. This shift is accompanied by a decline in both the fractal dimension of the crack distribution and the overall damage degree of the model.
The crack propagation behavior of brittle materials, such as rock, is often challenging to capture under explosive loading conditions. To address this issue, model experiments were conducted based on the theory of explosive damage, utilizing transparent polymethyl methacrylate as a surrogate material to simulate the fracture response of brittle materials. High-speed photography and computed tomography scanning were employed to investigate the dynamic fracture process and three-dimensional crack evolution under blast loading. In addition, 3D scanning technology was used to reconstruct the morphology of cracks and characterize the fracture surface features. The results indicate that under the sustained action of multi-stage explosive energy, cracks undergo repeated initiation and propagation. Initial cracks induced by shock waves exhibit high density and a “fish scale” pattern, primarily concentrated around the blast hole. In contrast, secondary cracks driven by detonation gases have a lower density and extend outward in “ear-shaped” or “dagger-shaped” forms. As the distance from the explosion center increases, the crack surface morphology transitions from rugged to microwave-like textures, with improved flatness. Specifically, the elevation variance of the fracture surface decreases from 0.796 to 0.586, while the maximum height reduces from 3.2 mm to 2.8 mm, representing a 12.5% reduction. Moreover, the failure mode of the material shifts from compressive-shear to tensile failure with increasing distance from the explosion center. This shift is accompanied by a decline in both the fractal dimension of the crack distribution and the overall damage degree of the model.
, Available online , doi: 10.11883/bzycj-2024-0300
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Blast wave damage and protection experiments conducted in large-scale shock tubes can avoid the inaccurate experimental results caused by the size effect in small-scale model experiments. However, due to the scarcity of equipment, there is still a lack of research on directly simulating the shock waveforms of explosive explosions using large-scale shock tubes at present. Therefore, a numerical simulation study of the generation and propagation process of shock wave generated by hydrogen-oxygen detonation in a large shock tube were conducted, and the reproduction of blast wave in a large shock tube was realized based on numerical simulation. Based on the designs of existing large shock tubes, a two-dimensional axisymmetric model of a large shock tube with driving tube, shock shaping section and variable angle outlet was established. The governing equation of a two-dimensional unsteady viscous compressible flow together with the seven-step reaction of the hydrogen-oxygen detonation mechanism was used to simulate the generation and propagation process of the shock wave. The renormalization group k-ε model was selected as the turbulence model, and the two-dimensional transient coupling solver was used for numerical simulation. Due to the large scale of the model, turbulence has little effect on the far-field shock wave. Therefore, the finite rate component transport model was selected to couple the interaction between turbulence and chemical reaction, and a two-dimensional transient coupled solver was used. Based on the numerical results, the influence of initial physical conditions of the driving gas, inert gas mixing, and the shock tube configurations on the formation of shock wave waveforms by detonation was studied. The variation laws of shock wave characteristic parameters under various factors were summarized. Finally, using the experimental data of black powder explosion shock waves as the target, the process of shock wave waveform regulation in the large shock tube was simulated according to the shock wave variation laws. The results show that under the combined effect of multiple factors, it is possible to simulate and reproduce the specific explosion shock wave using the hydrogen-oxygen detonation driving method in the large shock tube.
Blast wave damage and protection experiments conducted in large-scale shock tubes can avoid the inaccurate experimental results caused by the size effect in small-scale model experiments. However, due to the scarcity of equipment, there is still a lack of research on directly simulating the shock waveforms of explosive explosions using large-scale shock tubes at present. Therefore, a numerical simulation study of the generation and propagation process of shock wave generated by hydrogen-oxygen detonation in a large shock tube were conducted, and the reproduction of blast wave in a large shock tube was realized based on numerical simulation. Based on the designs of existing large shock tubes, a two-dimensional axisymmetric model of a large shock tube with driving tube, shock shaping section and variable angle outlet was established. The governing equation of a two-dimensional unsteady viscous compressible flow together with the seven-step reaction of the hydrogen-oxygen detonation mechanism was used to simulate the generation and propagation process of the shock wave. The renormalization group k-ε model was selected as the turbulence model, and the two-dimensional transient coupling solver was used for numerical simulation. Due to the large scale of the model, turbulence has little effect on the far-field shock wave. Therefore, the finite rate component transport model was selected to couple the interaction between turbulence and chemical reaction, and a two-dimensional transient coupled solver was used. Based on the numerical results, the influence of initial physical conditions of the driving gas, inert gas mixing, and the shock tube configurations on the formation of shock wave waveforms by detonation was studied. The variation laws of shock wave characteristic parameters under various factors were summarized. Finally, using the experimental data of black powder explosion shock waves as the target, the process of shock wave waveform regulation in the large shock tube was simulated according to the shock wave variation laws. The results show that under the combined effect of multiple factors, it is possible to simulate and reproduce the specific explosion shock wave using the hydrogen-oxygen detonation driving method in the large shock tube.
, Available online , doi: 10.11883/bzycj-2024-0153
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Impact ejecting is a critical part of the impact process and plays a pivotal role in engineering applications and scientific analyses in deep space exploration. Its importance extends to space missions such as asteroid surface anchoring for mission stability, impact sampling for scientific analysis of extraterrestrial materials, kinetic impact deflection for planetary defense strategies, and the detailed analysis of ejecta deposition patterns on planetary surfaces to understand surface evolution and regolith dynamics. With small asteroids whose surfaces are commonly covered with regolith, granular targets are employed in laboratory settings to simulate the impact ejecting process. This paper presents a review of the research progress concerning the behavior of impact ejecting on granular targets. The formation process of impact ejecting and methods for describing ejecta curtains are evaluated. An analysis of the dimensional similarity laws governing impact ejecta, along with their applicability and limitations, is conducted. Additionally, the influence of factors, such as target material parameters, impact conditions, target surface morphology, and impactor shape and structure, on impact ejecting behavior is summarized. Finally, existing research challenges are objectively identified, and potential directions for further scientific research about the behavior of impact ejecta on granular targets are proposed.
Impact ejecting is a critical part of the impact process and plays a pivotal role in engineering applications and scientific analyses in deep space exploration. Its importance extends to space missions such as asteroid surface anchoring for mission stability, impact sampling for scientific analysis of extraterrestrial materials, kinetic impact deflection for planetary defense strategies, and the detailed analysis of ejecta deposition patterns on planetary surfaces to understand surface evolution and regolith dynamics. With small asteroids whose surfaces are commonly covered with regolith, granular targets are employed in laboratory settings to simulate the impact ejecting process. This paper presents a review of the research progress concerning the behavior of impact ejecting on granular targets. The formation process of impact ejecting and methods for describing ejecta curtains are evaluated. An analysis of the dimensional similarity laws governing impact ejecta, along with their applicability and limitations, is conducted. Additionally, the influence of factors, such as target material parameters, impact conditions, target surface morphology, and impactor shape and structure, on impact ejecting behavior is summarized. Finally, existing research challenges are objectively identified, and potential directions for further scientific research about the behavior of impact ejecta on granular targets are proposed.
, Available online , doi: 10.11883/bzycj-2024-0365
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The evolution and distribution characteristics of cracks in presplit blasting can be significantly affected by the in-situ stress, often leading to issues such as over or under excavation in deep rock masses. In this paper, a theoretical model for presplit blasting under in-situ stress in rock engineering was developed based on the assumption of plane-strain problem of elastic mechanics. The propagation and attenuation of explosion stress waves were analyzed using a combination of Laplace transforms and numerical inversion. Furthermore, the impact of initial static stress on the blasting-induced dynamic stress field distribution in presplitting was examined and discussed. The Riedel-Hiermaier-Thoma (RHT) model in LS-DYNA code was employed to investigate the dynamic mechanical behavior of rock mass, and its material parameters were calibrated by comparing blasting crack patterns and the explosion pressure attenuation curves. Then, the validated model was used to simulate the damage features of rock presplit blasting under both hydrostatic and anisotropy pressure conditions, thereby analyzing the effects of the static stress and the dynamic pressure on the crack extension behavior. In addition, the distribution characteristics of blasting cracks are quantitatively characterized by the Hough transform method. The results indicate that the difficulty in crack coalescence for deep rock presplit blasting is primarily attributed to the reduction of tangential tensile stress caused by the in-situ stress. This prevents the formation of tensile fracture planes between boreholes due to restricted tangential displacements, which was demonstrated by the evolution of circumferential tensile stress and particle displacement vectors. Moreover, a crack coalescence criterion in presplit blasting was proposed to predict whether inter-borehole cracks penetrate based on the damage theory of stress wave superposition, and the relationship between charge diameter and hole spacing under various in-situ stress can guide the arrangement of boreholes, thus improving the presplit blasting effectiveness for deep rock.
The evolution and distribution characteristics of cracks in presplit blasting can be significantly affected by the in-situ stress, often leading to issues such as over or under excavation in deep rock masses. In this paper, a theoretical model for presplit blasting under in-situ stress in rock engineering was developed based on the assumption of plane-strain problem of elastic mechanics. The propagation and attenuation of explosion stress waves were analyzed using a combination of Laplace transforms and numerical inversion. Furthermore, the impact of initial static stress on the blasting-induced dynamic stress field distribution in presplitting was examined and discussed. The Riedel-Hiermaier-Thoma (RHT) model in LS-DYNA code was employed to investigate the dynamic mechanical behavior of rock mass, and its material parameters were calibrated by comparing blasting crack patterns and the explosion pressure attenuation curves. Then, the validated model was used to simulate the damage features of rock presplit blasting under both hydrostatic and anisotropy pressure conditions, thereby analyzing the effects of the static stress and the dynamic pressure on the crack extension behavior. In addition, the distribution characteristics of blasting cracks are quantitatively characterized by the Hough transform method. The results indicate that the difficulty in crack coalescence for deep rock presplit blasting is primarily attributed to the reduction of tangential tensile stress caused by the in-situ stress. This prevents the formation of tensile fracture planes between boreholes due to restricted tangential displacements, which was demonstrated by the evolution of circumferential tensile stress and particle displacement vectors. Moreover, a crack coalescence criterion in presplit blasting was proposed to predict whether inter-borehole cracks penetrate based on the damage theory of stress wave superposition, and the relationship between charge diameter and hole spacing under various in-situ stress can guide the arrangement of boreholes, thus improving the presplit blasting effectiveness for deep rock.
, Available online , doi: 10.11883/bzycj-2024-0356
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Axisymmetric conical structures, as a common configuration, induce oblique detonation waves exhibiting significantly greater structural complexity compared to those generated by sharp wedges. Numerical simulations of oblique detonation waves induced by a finite cone were performed using the open-source code OpenFOAM, with analysis conducted on post-detonation flow fields, wavefront structure, and detonation cell structures. The numerical results show that under the effect of the finite cone the flow field behind the detonation wave is successively influenced by Taylor-Maccoll flow and Prandtl-Meyer expansion waves. The pressure and Mach number along the streamlines at different positions on the detonation wave front exhibit oscillatory changes with the influence of these two physical processes and triple points on oblique detonation surfaces, and then tend to stabilize. Depending on the different post-detonation flow field, the detonation wave front structure is divided into four sections: smooth ZND (Zel’dovich-Neumann-Döring)-like structure, single-headed triple points cell-like structure, dual-headed triple points cell structure and dual-headed triple point structure influenced by Prandtl-Meyer. The shock pole curve theory is used to analyze the wave structures. It is found that the upstream-facing triple points exhibits higher detonation intensity, i.e., higher Mach number and pressure, compared to the downstream-facing triple points in dual-headed triple points structure. Finally, based on the above analysis, triple point traces are recorded to obtain four different cell structures: smooth planar structure, parallel line structure, oblique rhombus structure, and irregular oblique rhombus structure.
Axisymmetric conical structures, as a common configuration, induce oblique detonation waves exhibiting significantly greater structural complexity compared to those generated by sharp wedges. Numerical simulations of oblique detonation waves induced by a finite cone were performed using the open-source code OpenFOAM, with analysis conducted on post-detonation flow fields, wavefront structure, and detonation cell structures. The numerical results show that under the effect of the finite cone the flow field behind the detonation wave is successively influenced by Taylor-Maccoll flow and Prandtl-Meyer expansion waves. The pressure and Mach number along the streamlines at different positions on the detonation wave front exhibit oscillatory changes with the influence of these two physical processes and triple points on oblique detonation surfaces, and then tend to stabilize. Depending on the different post-detonation flow field, the detonation wave front structure is divided into four sections: smooth ZND (Zel’dovich-Neumann-Döring)-like structure, single-headed triple points cell-like structure, dual-headed triple points cell structure and dual-headed triple point structure influenced by Prandtl-Meyer. The shock pole curve theory is used to analyze the wave structures. It is found that the upstream-facing triple points exhibits higher detonation intensity, i.e., higher Mach number and pressure, compared to the downstream-facing triple points in dual-headed triple points structure. Finally, based on the above analysis, triple point traces are recorded to obtain four different cell structures: smooth planar structure, parallel line structure, oblique rhombus structure, and irregular oblique rhombus structure.
, Available online , doi: 10.11883/bzycj-2024-0333
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In order to study the initiation process of liquid explosive nitromethane containing cavities under shock wave loading, an Eulerian multi-material computational approach based on the level set method was developed. The reactive Euler equations were adopted as the governing equations, the level set method was utilized to track the multi-medium interface between the chemical reaction mixture and the cavity. To improve the robustness of calculation method, the modified ghost fluid method was applied in computational cells near the interface. Based on the modified ghost fluid method, a multi-medium problem was transformed into a single media problem. For these two fluid phases on both sides of the interface, the high order weighted essential non-oscillatory finite difference method was implemented to calculate the numerical fluxes on cell boundary, making the simulation results reliable. However, the Jones-Wilkins-Lee equation of state differs greatly from the ideal gas equation of state. In addition, the mass fraction of detonation product directly affects the transformation process between the conserved variables and the primitive variables in reaction zone, making it difficult to provide an explicit expression for the equation of state of explosive mixture. In order to solve the above problems, a ghost fluid state prediction method based on the Harten-Lax-van Leer-contact (HLLC ) approximate Riemann solver was developed. By dealing with a complex multi-medium Riemann problem considering chemical reaction, the variable states of ghost fluid on both sides of the interface can be obtained. The multi-medium calculation method was used to simulate the interaction problems between liquid nitromethane and the cavity under the loading condition with different impact strengths. The numerical results illustrate that the method proposed in the paper can capture the entire fluid dynamics process of cavity compression, cavity collapse, cavity closure and cavity disappearance.
In order to study the initiation process of liquid explosive nitromethane containing cavities under shock wave loading, an Eulerian multi-material computational approach based on the level set method was developed. The reactive Euler equations were adopted as the governing equations, the level set method was utilized to track the multi-medium interface between the chemical reaction mixture and the cavity. To improve the robustness of calculation method, the modified ghost fluid method was applied in computational cells near the interface. Based on the modified ghost fluid method, a multi-medium problem was transformed into a single media problem. For these two fluid phases on both sides of the interface, the high order weighted essential non-oscillatory finite difference method was implemented to calculate the numerical fluxes on cell boundary, making the simulation results reliable. However, the Jones-Wilkins-Lee equation of state differs greatly from the ideal gas equation of state. In addition, the mass fraction of detonation product directly affects the transformation process between the conserved variables and the primitive variables in reaction zone, making it difficult to provide an explicit expression for the equation of state of explosive mixture. In order to solve the above problems, a ghost fluid state prediction method based on the Harten-Lax-van Leer-contact (HLLC ) approximate Riemann solver was developed. By dealing with a complex multi-medium Riemann problem considering chemical reaction, the variable states of ghost fluid on both sides of the interface can be obtained. The multi-medium calculation method was used to simulate the interaction problems between liquid nitromethane and the cavity under the loading condition with different impact strengths. The numerical results illustrate that the method proposed in the paper can capture the entire fluid dynamics process of cavity compression, cavity collapse, cavity closure and cavity disappearance.
, Available online , doi: 10.11883/bzycj-2024-0268
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To investigate the explosion flame development and propagation mechanism of coated aluminum powder, a shell and core structure of stearic acid-coated aluminum powder (SA@Al) was prepared using the solvent evaporation method. The influence of dust concentration on the explosion flame propagation characteristics of SA@Al dust with coating concentrations of 5%, 10%, and 15% was experimentally studied using an improved Hartmann tube. Flame propagation behavior was observed through high-speed photography, and the flame propagation velocity was calculated. The kinetic characteristics of the gas-phase explosion reaction were analyzed using CHEMKIN-PRO software to reveal the mechanism of SA@Al dust explosion flame propagation. The results indicated that as the dust concentration increased, the fullness and continuity of the explosion flames for 5%, 10%, and 15% SA@Al dust first increased and then decreased, with the average flame propagation velocity showing a trend of first rising and then falling. The flame propagation velocity reached its maximum at a dust concentration of 500 g/m³. In contrast, the explosion flame propagation velocity of pure aluminum powder reached its maximum at 750 g/m³, suggesting that the stearic acid coating layer promotes the propagation of the aluminum powder explosion flame. Additionally, under each dust concentration, the explosion flame of 10% coating concentration SA@Al was the most intense, with the highest average flame propagation velocity. The temperature rise of the SA@Al explosion flame with different dust concentrations mainly consisted of two stages: a rapid heating stage and a slow heating stage. The rapid heating stage exhibited higher temperature sensitivity for reactions R2, R11, and R10, while the slow heating stage exhibited higher temperature sensitivity for reactions R5 and R11. The dust concentration significantly affected the rate of temperature rise in the slow heating stage, resulting in the highest explosion equilibrium temperature for SA@Al at 500 g/m³. The combustion of the stearic acid coating promoted the oxidation of the aluminum core, thereby strengthening the explosion reaction. However, high dust concentration led to limitations in O radicals, which weakened the reaction intensity to some extent.
To investigate the explosion flame development and propagation mechanism of coated aluminum powder, a shell and core structure of stearic acid-coated aluminum powder (SA@Al) was prepared using the solvent evaporation method. The influence of dust concentration on the explosion flame propagation characteristics of SA@Al dust with coating concentrations of 5%, 10%, and 15% was experimentally studied using an improved Hartmann tube. Flame propagation behavior was observed through high-speed photography, and the flame propagation velocity was calculated. The kinetic characteristics of the gas-phase explosion reaction were analyzed using CHEMKIN-PRO software to reveal the mechanism of SA@Al dust explosion flame propagation. The results indicated that as the dust concentration increased, the fullness and continuity of the explosion flames for 5%, 10%, and 15% SA@Al dust first increased and then decreased, with the average flame propagation velocity showing a trend of first rising and then falling. The flame propagation velocity reached its maximum at a dust concentration of 500 g/m³. In contrast, the explosion flame propagation velocity of pure aluminum powder reached its maximum at 750 g/m³, suggesting that the stearic acid coating layer promotes the propagation of the aluminum powder explosion flame. Additionally, under each dust concentration, the explosion flame of 10% coating concentration SA@Al was the most intense, with the highest average flame propagation velocity. The temperature rise of the SA@Al explosion flame with different dust concentrations mainly consisted of two stages: a rapid heating stage and a slow heating stage. The rapid heating stage exhibited higher temperature sensitivity for reactions R2, R11, and R10, while the slow heating stage exhibited higher temperature sensitivity for reactions R5 and R11. The dust concentration significantly affected the rate of temperature rise in the slow heating stage, resulting in the highest explosion equilibrium temperature for SA@Al at 500 g/m³. The combustion of the stearic acid coating promoted the oxidation of the aluminum core, thereby strengthening the explosion reaction. However, high dust concentration led to limitations in O radicals, which weakened the reaction intensity to some extent.
, Available online , doi: 10.11883/bzycj-2025-0047
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With the increasing speed of trains, the impacts of mechanical shock, arc heat, and Joule heat on the high-speed railway catenary system have become increasingly significant. The coupling effect of high temperature and impact load has emerged as a key limiting factor for the safe operation of the pantograph-catenary system. This study focuses on copper-magnesium alloy materials used in the catenary system to address the challenges of dynamic impact and friction-induced heat generation in high-speed railways. To investigate the mechanical properties of the high-speed railway pantograph-catenary system under service conditions such as dynamic impact and frictional temperature rise, a DF14.205D electronic universal testing machine and a split Hopkinson pressure bar were employed. The uniaxial compression mechanical properties of the copper-magnesium alloy in the catenary were tested over a strain rate range of 0.001 s−1 to3000 s−1 and a temperature range of 293 K to 873 K. The strain-rate effect and temperature sensitivity of the stress-strain response were carefully analyzed. The study also revealed the compression deformation mechanism and the evolution law of the alloy’s microstructure under the combined influence of strain rate and temperature. Furthermore, a dynamic constitutive model was established to accurately describe the plastic flow behavior of the material. The findings indicate that during compression, the copper-magnesium alloy materials exhibit significant strain-rate strengthening and temperature softening effects. These effects result from the combined action of work hardening, strain rate, and temperature softening. When the temperature exceeds 473 K, temperature softening becomes the dominant factor in material deformation, and the elevated temperature can stimulate dynamic recovery and dynamic recrystallization processes. The modified Johnson-Cook model was found to be capable of accurately predicting the plastic flow stress-strain response. These research outcomes provide valuable guidance and references for the safety design and evaluation of the high-speed train pantograph-catenary system during its service.
With the increasing speed of trains, the impacts of mechanical shock, arc heat, and Joule heat on the high-speed railway catenary system have become increasingly significant. The coupling effect of high temperature and impact load has emerged as a key limiting factor for the safe operation of the pantograph-catenary system. This study focuses on copper-magnesium alloy materials used in the catenary system to address the challenges of dynamic impact and friction-induced heat generation in high-speed railways. To investigate the mechanical properties of the high-speed railway pantograph-catenary system under service conditions such as dynamic impact and frictional temperature rise, a DF14.205D electronic universal testing machine and a split Hopkinson pressure bar were employed. The uniaxial compression mechanical properties of the copper-magnesium alloy in the catenary were tested over a strain rate range of 0.001 s−1 to
, Available online , doi: 10.11883/bzycj-2025-0054
Abstract:
In recent years, polyurea-coated reinforced concrete (RC) slabs have been extensively studied both experimentally and numerically for structural strengthening against contact explosions. However, theoretical investigations remain limited, particularly concerning the impact of polyurea on the local damages of the RC substrates. In this paper, an analytical model based on stress wave propagation theory was proposed to investigate the reflection of compression waves at the backside of the RC substrate slab and predict the spalling depth. Utilizing this analytical model, a quantitative and detailed discussion was presented regarding the effect of the polyurea on the critical spalling and breach of the RC substrate slab. Furthermore, the applicability of the empirical breach prediction, originally developed for uncoated RC slabs, was validated through existing experiments to predict the breach of polyurea-coated RC substrate slabs. The results indicate that polyurea affects the spalling process of the RC substrate slabs. Specifically, the net stress wave adjacent to the concrete-polyurea interface is a compression wave, while it transitions to a tensile wave in the deeper concrete. Polyurea primarily impacts the first spall of the RC substrate slab; subsequent spalling processes after the first spall align with those observed in uncoated RC slabs. Upon the occurrence of critical spalling, polyurea enhances the critical spalling resistance of RC slabs, although it significantly increases the spalling depth. Conversely, when a breach occurs, polyurea reduces the number of spalls but minimally affects on the total spalling depth. Based on these findings, the empirical method for predicting breaches of uncoated RC slabs can effectively be applied to predict the breach of RC substrate slabs coated with polyurea. The test results from more than twenty contact explosion experiments are consistent with the predicted outcomes, thereby validating the effectiveness of the analytical model and providing a method for estimating the breach of polyurea-coated RC substrate slabs.
In recent years, polyurea-coated reinforced concrete (RC) slabs have been extensively studied both experimentally and numerically for structural strengthening against contact explosions. However, theoretical investigations remain limited, particularly concerning the impact of polyurea on the local damages of the RC substrates. In this paper, an analytical model based on stress wave propagation theory was proposed to investigate the reflection of compression waves at the backside of the RC substrate slab and predict the spalling depth. Utilizing this analytical model, a quantitative and detailed discussion was presented regarding the effect of the polyurea on the critical spalling and breach of the RC substrate slab. Furthermore, the applicability of the empirical breach prediction, originally developed for uncoated RC slabs, was validated through existing experiments to predict the breach of polyurea-coated RC substrate slabs. The results indicate that polyurea affects the spalling process of the RC substrate slabs. Specifically, the net stress wave adjacent to the concrete-polyurea interface is a compression wave, while it transitions to a tensile wave in the deeper concrete. Polyurea primarily impacts the first spall of the RC substrate slab; subsequent spalling processes after the first spall align with those observed in uncoated RC slabs. Upon the occurrence of critical spalling, polyurea enhances the critical spalling resistance of RC slabs, although it significantly increases the spalling depth. Conversely, when a breach occurs, polyurea reduces the number of spalls but minimally affects on the total spalling depth. Based on these findings, the empirical method for predicting breaches of uncoated RC slabs can effectively be applied to predict the breach of RC substrate slabs coated with polyurea. The test results from more than twenty contact explosion experiments are consistent with the predicted outcomes, thereby validating the effectiveness of the analytical model and providing a method for estimating the breach of polyurea-coated RC substrate slabs.
, 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-2024-0366
Abstract:
In order to effectively predict and control the consequences of fuel-air mixture explosions in enclosed spaces and thereby reduce the casualties and property losses caused by accidents, the relationship between the explosive overpressure characteristics of fuel-air mixtures and the spatial scale of explosions was investigated. Closed square pipes with varying length-diameter ratios, volumes, and lengths were used to examine the impact of fuel-air mixture explosion overpressure characteristics by keeping the initial oil and gas concentration, ignition position, and ignition energy constant. The experimental results show that the rate of overpressure rise goes through three stages: a rapid increase period, a continuous oscillation period, and an attenuation termination period, which reveals the dynamic relationship between reaction rate and heat loss. The reduce of the nozzle area and the increase of the internal surface area of the pipeline can both lead to the decrease of the the maximum overpressure, the average overpressure rise rate, the maximum overpressure rise rate, and the explosion power. The further analysis of the experimental results reveals that the change in the nozzle area will directly affect the flame front area and reaction rate, with a more direct and significant impact on the maximum overpressure. The changes in the inner surface area have a relatively indirect effect on the maximum overpressure by regulating energy transfer and heat loss. Additionally, pipeline length is a crucial factor affecting the time to reach maximum overpressure. The increase of the pipeline not only increases the heat loss but also delays the superposition time point of the reflected wave and the incident wave, with the energy of the reflected wave undergoing relative attenuation.
In order to effectively predict and control the consequences of fuel-air mixture explosions in enclosed spaces and thereby reduce the casualties and property losses caused by accidents, the relationship between the explosive overpressure characteristics of fuel-air mixtures and the spatial scale of explosions was investigated. Closed square pipes with varying length-diameter ratios, volumes, and lengths were used to examine the impact of fuel-air mixture explosion overpressure characteristics by keeping the initial oil and gas concentration, ignition position, and ignition energy constant. The experimental results show that the rate of overpressure rise goes through three stages: a rapid increase period, a continuous oscillation period, and an attenuation termination period, which reveals the dynamic relationship between reaction rate and heat loss. The reduce of the nozzle area and the increase of the internal surface area of the pipeline can both lead to the decrease of the the maximum overpressure, the average overpressure rise rate, the maximum overpressure rise rate, and the explosion power. The further analysis of the experimental results reveals that the change in the nozzle area will directly affect the flame front area and reaction rate, with a more direct and significant impact on the maximum overpressure. The changes in the inner surface area have a relatively indirect effect on the maximum overpressure by regulating energy transfer and heat loss. Additionally, pipeline length is a crucial factor affecting the time to reach maximum overpressure. The increase of the pipeline not only increases the heat loss but also delays the superposition time point of the reflected wave and the incident wave, with the energy of the reflected wave undergoing relative attenuation.
, Available online , doi: 10.11883/bzycj-2025-0024
Abstract:
To investigate the penetration resistance of metal honeycomb tube-constrained concrete structures under hypervelocity impact, penetration experiments were conducted using a two-stage light gas gun with projectile velocities near 1 500 m/s. The material point method (MPM) was employed to simulate the penetration process and validate the reasonableness of target and projectile parameters. This method was further used to analyze the effects of honeycomb tube parameters, including wall thickness, height, diameter, and material, on the penetration resistance of the target structure. Numerical simulations showed that MPM can accurately simulate high-velocity penetration processes, with simulation results deviating from experimental data by less than 10%. Through orthogonal analysis, the factors influencing penetration depth were ranked in descending order as follows: characteristic tube depth, characteristic inner diameter, characteristic wall thickness, and material. For the cratering effect, the primary influencing factors were identified as characteristic wall thickness, characteristic tube depth, material, and characteristic inner diameter. For the projectiles tested in this study, optimization results indicated the following: A combination of 4 mm wall thickness, 150 mm height, 30 mm incircle diameter, and tungsten alloy demonstrated the best penetration resistance, reducing penetration depth by 25.1% compared to plain concrete. A combination of 4 mm wall thickness, 150 mm height, 90 mm incircle diameter, and aluminum exhibited superior resistance to the cratering effect, decreasing crater radius by 28.7% compared to plain concrete. Multi-objective optimization analysis determined the optimal overall configuration to be: 4 mm wall thickness, 150 mm height, 30 mm incircle diameter, and aluminum.
To investigate the penetration resistance of metal honeycomb tube-constrained concrete structures under hypervelocity impact, penetration experiments were conducted using a two-stage light gas gun with projectile velocities near 1 500 m/s. The material point method (MPM) was employed to simulate the penetration process and validate the reasonableness of target and projectile parameters. This method was further used to analyze the effects of honeycomb tube parameters, including wall thickness, height, diameter, and material, on the penetration resistance of the target structure. Numerical simulations showed that MPM can accurately simulate high-velocity penetration processes, with simulation results deviating from experimental data by less than 10%. Through orthogonal analysis, the factors influencing penetration depth were ranked in descending order as follows: characteristic tube depth, characteristic inner diameter, characteristic wall thickness, and material. For the cratering effect, the primary influencing factors were identified as characteristic wall thickness, characteristic tube depth, material, and characteristic inner diameter. For the projectiles tested in this study, optimization results indicated the following: A combination of 4 mm wall thickness, 150 mm height, 30 mm incircle diameter, and tungsten alloy demonstrated the best penetration resistance, reducing penetration depth by 25.1% compared to plain concrete. A combination of 4 mm wall thickness, 150 mm height, 90 mm incircle diameter, and aluminum exhibited superior resistance to the cratering effect, decreasing crater radius by 28.7% compared to plain concrete. Multi-objective optimization analysis determined the optimal overall configuration to be: 4 mm wall thickness, 150 mm height, 30 mm incircle diameter, and aluminum.
, Available online , doi: 10.11883/bzycj-2025-0058
Abstract:
To address the fracture problem of dynamic submarine cables and their protective sheaths caused by friction and collision with wind turbine platforms under harsh sea conditions, a multi-impact resistant composite protective layer was designed using EVA foam and rubber as the main materials, which possess high elasticity and excellent cushioning properties.Mechanical property tests were conducted on EVA foam materials with various relative densities under different loading conditions using a universal testing machine and drop hammer. Energy absorption efficiency, densification strain, plateau stress and maximum specific energy absorption were introduced to characterize the mechanical properties of EVA foam. The effects of relative density, strain rate and repeated loading on the energy absorption characteristics of EVA foam were revealed.Based on the matching relationship between the energy absorption per unit volume of EVA foam and the kinetic energy of dynamic submarine cables to be absorbed, the optimal thickness of the protective layer was determined, and composite protective layer specimens were fabricated. Subsequently, drop hammer impact tests were performed to compare the cushioning and energy absorption characteristics of the composite protective layer with other materials, preliminarily verifying its high energy absorption efficiency. Further drop hammer impact tests were conducted to investigate the effects of impact energy and loading cycles on the cushioning and energy absorption characteristics of the composite protective layer. The experimental results showed that: (1) Under single impact, the peak force and maximum displacement of the composite protective layer showed a linear positive correlation with the drop hammer mass and impact velocity, with energy absorption efficiency reaching 85 %; (2) Under multiple impacts, the mechanical properties of the composite protective layer exhibited remarkable stability - the maximum displacement in the fourth impact increased by only 5.5 % compared to the first impact, with fluctuations in energy absorption value and instantaneous rebound rate remaining below 5 %. The composite protective layer demonstrates unique mechanical properties that provide effective long-term protection for dynamic submarine cables under harsh marine conditions.
To address the fracture problem of dynamic submarine cables and their protective sheaths caused by friction and collision with wind turbine platforms under harsh sea conditions, a multi-impact resistant composite protective layer was designed using EVA foam and rubber as the main materials, which possess high elasticity and excellent cushioning properties.Mechanical property tests were conducted on EVA foam materials with various relative densities under different loading conditions using a universal testing machine and drop hammer. Energy absorption efficiency, densification strain, plateau stress and maximum specific energy absorption were introduced to characterize the mechanical properties of EVA foam. The effects of relative density, strain rate and repeated loading on the energy absorption characteristics of EVA foam were revealed.Based on the matching relationship between the energy absorption per unit volume of EVA foam and the kinetic energy of dynamic submarine cables to be absorbed, the optimal thickness of the protective layer was determined, and composite protective layer specimens were fabricated. Subsequently, drop hammer impact tests were performed to compare the cushioning and energy absorption characteristics of the composite protective layer with other materials, preliminarily verifying its high energy absorption efficiency. Further drop hammer impact tests were conducted to investigate the effects of impact energy and loading cycles on the cushioning and energy absorption characteristics of the composite protective layer. The experimental results showed that: (1) Under single impact, the peak force and maximum displacement of the composite protective layer showed a linear positive correlation with the drop hammer mass and impact velocity, with energy absorption efficiency reaching 85 %; (2) Under multiple impacts, the mechanical properties of the composite protective layer exhibited remarkable stability - the maximum displacement in the fourth impact increased by only 5.5 % compared to the first impact, with fluctuations in energy absorption value and instantaneous rebound rate remaining below 5 %. The composite protective layer demonstrates unique mechanical properties that provide effective long-term protection for dynamic submarine cables under harsh marine conditions.
, Available online , doi: 10.11883/bzycj-2024-0502
Abstract:
Porous materials are accompanied by pore collapse behavior during impact compression. Based on the shock wave structure observed in experiments carried out by predecessors, the theoretically analysis of the relationship between the shock wave formation process and pore collapse behavior of porous materials is made. Firstly, considering the compression curve characteristics of porous materials and the overtaking of shock wave, it is proposed that the shock wave structure of porous materials has three modes: low pressure single wave mode, double shock wave mode and high pressure single wave mode. These different shock wave modes are mainly caused by the influence of elastic-plastic mechanical behavior in pore collapse on the compression curve of porous materials. Furthermore, combined with the Wu-Jing equation of state, the calculation method of shock compression characteristics compatible with different shock wave modes is developed. The relationship between the Hugoniot Curve of porous material and dense material is established, and the calculation equation of impact specific volume compatible with single shock wave mode is obtained, which can directly calculate the critical specific volume without approximate conditions. In addition, the equation of pore collapse established by Carroll is modified by taking the linear approximation of the variation of porosity with pressure in the elastic stage and the elastic-plastic stage, and considering the relationship between the stress of the matrix material and the macroscopic stress in the porous material. Based on the calculation model of shock compression characteristics considering pore collapse behavior, the Hugoniot data of the material are calculated, and the influence of pore collapse behavior on the shock compression characteristics of porous materials is discussed. The results show that the shock compression characteristics of the material are significantly affected by the pore collapse behavior at lower pressures, and the model in this paper can predict the shock wave parameters of porous materials more accurately.
Porous materials are accompanied by pore collapse behavior during impact compression. Based on the shock wave structure observed in experiments carried out by predecessors, the theoretically analysis of the relationship between the shock wave formation process and pore collapse behavior of porous materials is made. Firstly, considering the compression curve characteristics of porous materials and the overtaking of shock wave, it is proposed that the shock wave structure of porous materials has three modes: low pressure single wave mode, double shock wave mode and high pressure single wave mode. These different shock wave modes are mainly caused by the influence of elastic-plastic mechanical behavior in pore collapse on the compression curve of porous materials. Furthermore, combined with the Wu-Jing equation of state, the calculation method of shock compression characteristics compatible with different shock wave modes is developed. The relationship between the Hugoniot Curve of porous material and dense material is established, and the calculation equation of impact specific volume compatible with single shock wave mode is obtained, which can directly calculate the critical specific volume without approximate conditions. In addition, the equation of pore collapse established by Carroll is modified by taking the linear approximation of the variation of porosity with pressure in the elastic stage and the elastic-plastic stage, and considering the relationship between the stress of the matrix material and the macroscopic stress in the porous material. Based on the calculation model of shock compression characteristics considering pore collapse behavior, the Hugoniot data of the material are calculated, and the influence of pore collapse behavior on the shock compression characteristics of porous materials is discussed. The results show that the shock compression characteristics of the material are significantly affected by the pore collapse behavior at lower pressures, and the model in this paper can predict the shock wave parameters of porous materials more accurately.
, Available online , doi: 10.11883/bzycj-2024-0514
Abstract:
Due to the rapid development of military technology, there are more deployments of new arms, high-tech weapons and large-caliber shells in regional and local warfare, contributing to a sharp surge in the incidences of craniocerebral trauma among military personnel due to blast shockwaves. Thus, blast-induced traumatic brain injury at present is considered as one of the most prominent forms of injury on the battlefield. In order to assess the craniocerebral injury of personnel under the effect of the blast shock wave, it is urgent to establish a set of scientific, rational and comprehensive evaluation methods. Using a realistic physical manikin model with Chinese human body size characteristics and a sensing system to carry out three kinds of shock wave intensity shock tube experiments, this study systematically obtained the change process of head surface overpressure, head centroid acceleration and angular velocity as well as neck force and torque of the realistic physical manikin model with time. Based on the short-term and long-term injury effects of the explosion on the human cranium and brain, based on the 3 ms criterion, head injury criterion (HIC), brain injury criteria (BrIC) and neck injury indicators to determine the damage and the degree of damage to the human body to carry out a comprehensive research and judgment. The results showed that under three different strong shockwave environments, the shock wave overpressure duration was less than 5 ms, acceleration and neck force lasted 5~6 ms, and angular velocity and neck torque lasted 50~244 ms; the peak centroid resultant acceleration in the head of the realistic physical manikin model was (54.60±3.69)g, (102.00±1.72)g and (161.50±6.36)g, and the calculated HIC15 showed that the head injury threshold was not reached; according to the combined determination of head surface pressure load and BrIC, the probability of craniocerebral injury increased significantly, and protective measures should be taken to reduce the risk of injury.
Due to the rapid development of military technology, there are more deployments of new arms, high-tech weapons and large-caliber shells in regional and local warfare, contributing to a sharp surge in the incidences of craniocerebral trauma among military personnel due to blast shockwaves. Thus, blast-induced traumatic brain injury at present is considered as one of the most prominent forms of injury on the battlefield. In order to assess the craniocerebral injury of personnel under the effect of the blast shock wave, it is urgent to establish a set of scientific, rational and comprehensive evaluation methods. Using a realistic physical manikin model with Chinese human body size characteristics and a sensing system to carry out three kinds of shock wave intensity shock tube experiments, this study systematically obtained the change process of head surface overpressure, head centroid acceleration and angular velocity as well as neck force and torque of the realistic physical manikin model with time. Based on the short-term and long-term injury effects of the explosion on the human cranium and brain, based on the 3 ms criterion, head injury criterion (HIC), brain injury criteria (BrIC) and neck injury indicators to determine the damage and the degree of damage to the human body to carry out a comprehensive research and judgment. The results showed that under three different strong shockwave environments, the shock wave overpressure duration was less than 5 ms, acceleration and neck force lasted 5~6 ms, and angular velocity and neck torque lasted 50~244 ms; the peak centroid resultant acceleration in the head of the realistic physical manikin model was (54.60±3.69)g, (102.00±1.72)g and (161.50±6.36)g, and the calculated HIC15 showed that the head injury threshold was not reached; according to the combined determination of head surface pressure load and BrIC, the probability of craniocerebral injury increased significantly, and protective measures should be taken to reduce the risk of injury.
, Available online , doi: 10.11883/bzycj-2024-0493
Abstract:
Explosion venting is one of the effective ways to prevent and control the hazards of combustible gas explosions, but the process of venting there may be a secondary explosion of the external venting gas cloud, how to achieve an effective explosion venting of combustible gas explosions to reduce the hazards posed by the explosion, has become a key direction of the current research. To this end, from the combustible gas explosion characteristics, combustible gas explosion venting characteristics and explosion venting of the external flow field of the secondary explosion and other aspects of the current domestic and foreign combustible gas explosion venting characteristics of the current research situation is summarized and analyzed, and found that the explosion risk of the pluralistic mixed system is difficult to accurately predict and evaluate, the internal and external flow field coupling explosion venting mechanism is not yet in-depth, the characterization of the explosion venting effect and the critical conditions of the secondary explosion is unknown. Based on the above problems, the outlook from the exploration of combustible gas explosion risk and disaster-causing mechanism, deepen the combustible gas explosion venting overpressure and flame evolution characteristics of the study, revealing the formation mechanism of the secondary explosion of the explosion venting external flow field. This provides an important reference for the future study of combustible gas explosion venting.
Explosion venting is one of the effective ways to prevent and control the hazards of combustible gas explosions, but the process of venting there may be a secondary explosion of the external venting gas cloud, how to achieve an effective explosion venting of combustible gas explosions to reduce the hazards posed by the explosion, has become a key direction of the current research. To this end, from the combustible gas explosion characteristics, combustible gas explosion venting characteristics and explosion venting of the external flow field of the secondary explosion and other aspects of the current domestic and foreign combustible gas explosion venting characteristics of the current research situation is summarized and analyzed, and found that the explosion risk of the pluralistic mixed system is difficult to accurately predict and evaluate, the internal and external flow field coupling explosion venting mechanism is not yet in-depth, the characterization of the explosion venting effect and the critical conditions of the secondary explosion is unknown. Based on the above problems, the outlook from the exploration of combustible gas explosion risk and disaster-causing mechanism, deepen the combustible gas explosion venting overpressure and flame evolution characteristics of the study, revealing the formation mechanism of the secondary explosion of the explosion venting external flow field. This provides an important reference for the future study of combustible gas explosion venting.
, 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-2024-0280
Abstract:
Aiming to investigate the performance and design approach of the carbon fiber reinforced polymer (CFRP) sheet strengthened masonry infilled walls subjected to blast loads, the commercial finite element program LS-DYNA is firstly used to develop the simplified micro-finite element model of masonry infilled walls and the corresponding blast-resistant analysis model of the CFRP sheet strengthened walls. By comparing the numerical simulation results with the nine groups field explosion test results of the unstrengthening and CFRP sheet strengthened masonry infilled walls, the applicability of the present simplified micro-modeling approach, as well as the material models and parameters of masonry and CFRP sheet and the corresponding contact algorithm, is thoroughly verified. Furthermore, referring to the CFRP sheet seismic strengthening methods recommended by Chinese standard GB 50608—2020, the dynamic behaviors of the prototype masonry infilled walls strengthened with CFRP sheets under blast loads are analyzed and compared. It is recommended that the diagonal two-way strengthening method be advocated, followed by the vertical two-way and horizontal full-cover strengthening methods. In contrast, the vertical full-cover and mixed three-way strengthening methods are not recommended. Finally, to simultaneously satisfy the conditions of intact CFRP, no scattering debris and the peak central deflection than wall thickness to meet the blast-resistant design goal, the ranges of the scaled distance of the prototype masonry infilled walls with different arrangements of tie bar (non-/cut-off/full-length tie bar) that need to be strengthened under typical sedan (227 kg equivalent TNT) and briefcase bombs (23 kg equivalent TNT) specified by Federal Emergency Management Agency explode at different scaled distances are determined to be 0.8–2.0 m/kg1/3 and 0.2–1.2 m/kg1/3, respectively. The suggestions for the optimal number of CFRP sheet layers for effective blast-resistant design are further provided. The arrangement of the tie bar has little effect on the optimal number of strengthening layers, only affecting the critical scaled distance at which the wall needs to be strengthened.
Aiming to investigate the performance and design approach of the carbon fiber reinforced polymer (CFRP) sheet strengthened masonry infilled walls subjected to blast loads, the commercial finite element program LS-DYNA is firstly used to develop the simplified micro-finite element model of masonry infilled walls and the corresponding blast-resistant analysis model of the CFRP sheet strengthened walls. By comparing the numerical simulation results with the nine groups field explosion test results of the unstrengthening and CFRP sheet strengthened masonry infilled walls, the applicability of the present simplified micro-modeling approach, as well as the material models and parameters of masonry and CFRP sheet and the corresponding contact algorithm, is thoroughly verified. Furthermore, referring to the CFRP sheet seismic strengthening methods recommended by Chinese standard GB 50608—2020, the dynamic behaviors of the prototype masonry infilled walls strengthened with CFRP sheets under blast loads are analyzed and compared. It is recommended that the diagonal two-way strengthening method be advocated, followed by the vertical two-way and horizontal full-cover strengthening methods. In contrast, the vertical full-cover and mixed three-way strengthening methods are not recommended. Finally, to simultaneously satisfy the conditions of intact CFRP, no scattering debris and the peak central deflection than wall thickness to meet the blast-resistant design goal, the ranges of the scaled distance of the prototype masonry infilled walls with different arrangements of tie bar (non-/cut-off/full-length tie bar) that need to be strengthened under typical sedan (227 kg equivalent TNT) and briefcase bombs (23 kg equivalent TNT) specified by Federal Emergency Management Agency explode at different scaled distances are determined to be 0.8–2.0 m/kg1/3 and 0.2–1.2 m/kg1/3, respectively. The suggestions for the optimal number of CFRP sheet layers for effective blast-resistant design are further provided. The arrangement of the tie bar has little effect on the optimal number of strengthening layers, only affecting the critical scaled distance at which the wall needs to be strengthened.
, 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-Euler 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-Euler 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-2025-0106
Abstract:
To investigate the evolution of phase structure, dislocation distribution, energy absorption capacity, and impact accumulation effect of high-entropy alloys (HEA) under shock loading, molecular dynamics simulations were employed to systematically analyze the dynamic response behavior of Al0.3CoCrFeNi HEA plate subjected to single and secondary impact load. The results show that under the first impact, the phase structure evolution and energy absorption mode of the plastic region of Al0.3CoCrFeNi HEA plate exhibits significant velocity dependence. As the speed increases, the proportion of face-centered cubic structure shows a three-stage downward trend, while the disorder structure increases accordingly. Under low velocity impact (0.5-1.0 km/s), energy is mainly absorbed by dislocation network; at medium velocity impact (1.0-2.0 km/s), both dislocations and disordered atoms contribute; under high velocity impact (2.0-3.0 km/s), disordered atoms dominate energy absorption. Within the velocity range of 0.5-0.8 km/s of the rigid sphere, the dislocation line length increases linearly with the impact velocity. However, at higher impact velocities, the dislocation line length decreases due to the limitation of the plate thickness. The stress analysis shows that when the impact velocity increases, both the maximum stress and the boundary stress of the plastic zone exhibit nonlinear variations characterized by a quadratic relationship. Under the secondary impact, the Al0.3CoCrFeNi HEA plate forms a damage zone resembling a trapezoidal shape after impact. The radius of the pit within this damage zone exhibits a quadratic relationship with the impact velocity. Additionally, the minimum affected area resulting from the secondary impact also demonstrates a quadratic relationship with the impact velocity. Regarding impact resistance, as the initial impact velocity increases, the residual velocity following the secondary impact also rises, indicating a reduction in the resistance capability of HEA. At a distance of 10 nm from the impact center, the ballistic limit velocity decreases nonlinearly with increasing initial impact velocity. However, an increase in the secondary impact velocity mitigates the effects induced by the initial impact.
To investigate the evolution of phase structure, dislocation distribution, energy absorption capacity, and impact accumulation effect of high-entropy alloys (HEA) under shock loading, molecular dynamics simulations were employed to systematically analyze the dynamic response behavior of Al0.3CoCrFeNi HEA plate subjected to single and secondary impact load. The results show that under the first impact, the phase structure evolution and energy absorption mode of the plastic region of Al0.3CoCrFeNi HEA plate exhibits significant velocity dependence. As the speed increases, the proportion of face-centered cubic structure shows a three-stage downward trend, while the disorder structure increases accordingly. Under low velocity impact (0.5-1.0 km/s), energy is mainly absorbed by dislocation network; at medium velocity impact (1.0-2.0 km/s), both dislocations and disordered atoms contribute; under high velocity impact (2.0-3.0 km/s), disordered atoms dominate energy absorption. Within the velocity range of 0.5-0.8 km/s of the rigid sphere, the dislocation line length increases linearly with the impact velocity. However, at higher impact velocities, the dislocation line length decreases due to the limitation of the plate thickness. The stress analysis shows that when the impact velocity increases, both the maximum stress and the boundary stress of the plastic zone exhibit nonlinear variations characterized by a quadratic relationship. Under the secondary impact, the Al0.3CoCrFeNi HEA plate forms a damage zone resembling a trapezoidal shape after impact. The radius of the pit within this damage zone exhibits a quadratic relationship with the impact velocity. Additionally, the minimum affected area resulting from the secondary impact also demonstrates a quadratic relationship with the impact velocity. Regarding impact resistance, as the initial impact velocity increases, the residual velocity following the secondary impact also rises, indicating a reduction in the resistance capability of HEA. At a distance of 10 nm from the impact center, the ballistic limit velocity decreases nonlinearly with increasing initial impact velocity. However, an increase in the secondary impact velocity mitigates the effects induced by the initial impact.
, Available online , doi: 10.11883/bzycj-2024-0442
Abstract:
A closed space model was constructed using steel plates to examine the influence of afterburning energy load generated by explosive detonation products on the damage characteristics of confined space. Additionally, the quasi-static pressure in the confined space was simplified by applying the energy conservation law. Relying on the adiabatic index of the mixture of detonation products and air, as well as the complete afterburning degree of detonation products, a simulation method for the afterburning effect was proposed. This method was used to calculate the afterburning energy of detonation products and determine the beginning and ending times of the afterburning effect. The numerical simulation of implosion ruin in a confined space was carried out by this method. The implosion simulation considering the afterburning energy load was performed by employing two simulation methods: constant reaction rate and linearly increasing reaction rate. The results were compared with the implosion simulation results without considering the afterburning effect. The influence and degree of change of the afterburning effect on the implosion damage characteristics were analyzed. It is found that the afterburning effect with different reaction rates has a significant influence on the detonation damage characteristics, except for the temperature, in confined spaces. Moreover, the enhancement effect of the constant reaction rate is the most significant. It increased the velocity and acceleration loads under implosion in the confined space by 42.67% and 71.21%, respectively. The overpressure and quasi-static pressure were increased by 74.42% and 74.95%, respectively, and the kinetic energy was increased by approximately 212%. The proposed simulation method for the afterburning effect can better simulate the dynamic response of implosion ruin in confined spaces and provides a more accurate simulation method of the afterburning effect for the design and evaluation of explosion-proof structures.
A closed space model was constructed using steel plates to examine the influence of afterburning energy load generated by explosive detonation products on the damage characteristics of confined space. Additionally, the quasi-static pressure in the confined space was simplified by applying the energy conservation law. Relying on the adiabatic index of the mixture of detonation products and air, as well as the complete afterburning degree of detonation products, a simulation method for the afterburning effect was proposed. This method was used to calculate the afterburning energy of detonation products and determine the beginning and ending times of the afterburning effect. The numerical simulation of implosion ruin in a confined space was carried out by this method. The implosion simulation considering the afterburning energy load was performed by employing two simulation methods: constant reaction rate and linearly increasing reaction rate. The results were compared with the implosion simulation results without considering the afterburning effect. The influence and degree of change of the afterburning effect on the implosion damage characteristics were analyzed. It is found that the afterburning effect with different reaction rates has a significant influence on the detonation damage characteristics, except for the temperature, in confined spaces. Moreover, the enhancement effect of the constant reaction rate is the most significant. It increased the velocity and acceleration loads under implosion in the confined space by 42.67% and 71.21%, respectively. The overpressure and quasi-static pressure were increased by 74.42% and 74.95%, respectively, and the kinetic energy was increased by approximately 212%. The proposed simulation method for the afterburning effect can better simulate the dynamic response of implosion ruin in confined spaces and provides a more accurate simulation method of the afterburning effect for the design and evaluation of explosion-proof structures.
, Available online , doi: 10.11883/bzycj-2024-0309
Abstract:
This study investigates the dynamic response characteristics of silica sand under dynamic loading, employing a modified split Hopkinson pressure bar (SHPB) to gain insights into its crushing behavior and energy absorption properties. Four distinct grain size (2.5–5.0 mm, 1.25–2.5 mm, 0.6–1.25 mm, and <0.3 mm) were analyzed, with results demonstrating that the dynamic stress-strain behavior of silica sand is affected by both grain size and strain rate. The deformation process of silica sand is categorized into three stages: elastic, yielding, and plastic. Plastic compaction is dominant during the yielding stage, whereas crushing compaction prevails in the plastic stage. The relative breakage of particles shows a positive correlation with both strain rate and effective particle size, and an inverse correlation with fractal dimension. The impact of particle size on energy absorption efficiency is influenced by factors such as mineral composition, particle size, and differentiation degree. Under identical stress levels, larger particle sizes demonstrate greater energy absorption efficiency; similarly, under identical loading strain rates, larger particles exhibit lower peak stress. To improve sand's energy absorption efficiency and reduce required loading levels, sand with larger particle sizes is recommended.
This study investigates the dynamic response characteristics of silica sand under dynamic loading, employing a modified split Hopkinson pressure bar (SHPB) to gain insights into its crushing behavior and energy absorption properties. Four distinct grain size (2.5–5.0 mm, 1.25–2.5 mm, 0.6–1.25 mm, and <0.3 mm) were analyzed, with results demonstrating that the dynamic stress-strain behavior of silica sand is affected by both grain size and strain rate. The deformation process of silica sand is categorized into three stages: elastic, yielding, and plastic. Plastic compaction is dominant during the yielding stage, whereas crushing compaction prevails in the plastic stage. The relative breakage of particles shows a positive correlation with both strain rate and effective particle size, and an inverse correlation with fractal dimension. The impact of particle size on energy absorption efficiency is influenced by factors such as mineral composition, particle size, and differentiation degree. Under identical stress levels, larger particle sizes demonstrate greater energy absorption efficiency; similarly, under identical loading strain rates, larger particles exhibit lower peak stress. To improve sand's energy absorption efficiency and reduce required loading levels, sand with larger particle sizes is recommended.
, Available online , doi: 10.11883/bzycj-2024-0463
Abstract:
In the construction process of drilling and blasting method for layered rock tunnel, the unbalanced distribution of explosion energy was easy to cause serious over- and under-excavation. The joint dip angle, inter-hole delay, and hole spacing were the main influencing parameters. The simulated rock mass samples with different joint dip angles were prepared by the layered pouring method, and the blasting test of layered rock mass was carried out. Based on the ABAQUS simulation software, the blasting crack propagation and stress wave propagation characteristics of layered rock mass under different joint dip angles were analyzed. The results show that the joint dip angle has a significant guiding effect on the stress wave propagation. By affecting the stress distribution, the peak strain and damage degree at different positions are different, which in turn promotes the crack propagation at the joint surface or around the blast hole. The inter-hole delay plays a key role in regulating the crack propagation path. With the increase of delay time, the stress wave superposition area of the pre-blasting hole and the post-blasting hole gradually shifts from the joint center to the surrounding of the post-blasting hole, resulting in the peak strain and damage value of the joint center increasing first and then decreasing, and the failure area of the rock mass shifts to the post-blasting hole accordingly. However, too long delay weakens the synergistic effect of the double-hole stress wave. The increase of hole spacing weakens the stress superposition in the center of the joint, so that the energy is concentrated around the borehole, and the crack propagation mode changes from joint penetration to radial distribution around the borehole. However, too large a hole spacing is easy to lead to the failure of crack penetration between holes due to insufficient energy attenuation and stress superposition, which significantly reduces the crushing efficiency of rock mass. The research results are helpful to the understanding of blasting crack propagation in layered rock mass.
In the construction process of drilling and blasting method for layered rock tunnel, the unbalanced distribution of explosion energy was easy to cause serious over- and under-excavation. The joint dip angle, inter-hole delay, and hole spacing were the main influencing parameters. The simulated rock mass samples with different joint dip angles were prepared by the layered pouring method, and the blasting test of layered rock mass was carried out. Based on the ABAQUS simulation software, the blasting crack propagation and stress wave propagation characteristics of layered rock mass under different joint dip angles were analyzed. The results show that the joint dip angle has a significant guiding effect on the stress wave propagation. By affecting the stress distribution, the peak strain and damage degree at different positions are different, which in turn promotes the crack propagation at the joint surface or around the blast hole. The inter-hole delay plays a key role in regulating the crack propagation path. With the increase of delay time, the stress wave superposition area of the pre-blasting hole and the post-blasting hole gradually shifts from the joint center to the surrounding of the post-blasting hole, resulting in the peak strain and damage value of the joint center increasing first and then decreasing, and the failure area of the rock mass shifts to the post-blasting hole accordingly. However, too long delay weakens the synergistic effect of the double-hole stress wave. The increase of hole spacing weakens the stress superposition in the center of the joint, so that the energy is concentrated around the borehole, and the crack propagation mode changes from joint penetration to radial distribution around the borehole. However, too large a hole spacing is easy to lead to the failure of crack penetration between holes due to insufficient energy attenuation and stress superposition, which significantly reduces the crushing efficiency of rock mass. The research results are helpful to the understanding of blasting crack propagation in layered rock mass.
, Available online , doi: 10.11883/bzycj-2024-0282
Abstract:
Hydrogen-doped natural gas technology has been gradually used in pipeline transportation, but hydrogen-doped natural gas is prone to leakage and explosion accidents. The study used a 20L spherical device to investigate the effects of hydrogen blending ratio and CO2 addition on the explosion pressure and flame propagation characteristics of hydrogen-doped natural gas, and the chemical reaction kinetics method was used to analyse the explosion mechanism. The results showed that the hydrogen doping ratio has a promoting effect on the hydrogen-doped natural gas explosion pressure parameters and flame propagation speed. As the hydrogen doping ratio increases, the maximum explosion pressure gradually increases, the rapid burn time and sustained burn time are gradually decreasing. The maximum explosion pressure rise rate and flame propagation speed gradually increase when the hydrogen doping ratio is less than 0.5. When the hydrogen doping ratio is greater than 0.5, the maximum explosion pressure rise rate and flame propagation speed rise rapidly. The addition of CO2 has an inhibitory effect on the explosion pressure and flame propagation speed of the mixed gas, but the suppression effect on pressure parameters with high hydrogen doping ratio is poor. Through reaction kinetic analysis, it can be seen that as the hydrogen doping ratio increases, the laminar burning velocity and adiabatic flame temperature gradually increase, the mole fraction of active free radicals and the rate of product increase significantly, and the mixing of hydrogen changes the reaction path of methane. When the hydrogen doping ratio is greater than 0.5, reactions R84, R46 and R3 enter the top ten steps of the reaction, producing H and OH radicals, which promotes the reaction. CO2 can reduce the laminar burning velocity, adiabatic flame temperature, active free radical mole fraction and rate of production of the mixed gas, but adding CO2 does not change the reaction path of methane.
Hydrogen-doped natural gas technology has been gradually used in pipeline transportation, but hydrogen-doped natural gas is prone to leakage and explosion accidents. The study used a 20L spherical device to investigate the effects of hydrogen blending ratio and CO2 addition on the explosion pressure and flame propagation characteristics of hydrogen-doped natural gas, and the chemical reaction kinetics method was used to analyse the explosion mechanism. The results showed that the hydrogen doping ratio has a promoting effect on the hydrogen-doped natural gas explosion pressure parameters and flame propagation speed. As the hydrogen doping ratio increases, the maximum explosion pressure gradually increases, the rapid burn time and sustained burn time are gradually decreasing. The maximum explosion pressure rise rate and flame propagation speed gradually increase when the hydrogen doping ratio is less than 0.5. When the hydrogen doping ratio is greater than 0.5, the maximum explosion pressure rise rate and flame propagation speed rise rapidly. The addition of CO2 has an inhibitory effect on the explosion pressure and flame propagation speed of the mixed gas, but the suppression effect on pressure parameters with high hydrogen doping ratio is poor. Through reaction kinetic analysis, it can be seen that as the hydrogen doping ratio increases, the laminar burning velocity and adiabatic flame temperature gradually increase, the mole fraction of active free radicals and the rate of product increase significantly, and the mixing of hydrogen changes the reaction path of methane. When the hydrogen doping ratio is greater than 0.5, reactions R84, R46 and R3 enter the top ten steps of the reaction, producing H and OH radicals, which promotes the reaction. CO2 can reduce the laminar burning velocity, adiabatic flame temperature, active free radical mole fraction and rate of production of the mixed gas, but adding CO2 does not change the reaction path of methane.
, Available online , doi: 10.11883/bzycj-2024-0381
Abstract:
To investigate the propagation process of shock waves within a channel under different explosive yields and charge positions, this study established an experimental channel designed for individual soldier transit. Through experiments and simulations, it is found that the quantity and position of the charge affect the time history of overpressure and shock wave parameters. Within the tunnel, the propagation velocity and overpressure peak of the shock wave decreased with increasing of distance, while the duration and impulse of positive overpressure continuously extend and increase. When the charge equivalent increases, all shock wave parameters are enhanced, though the influence on the rate of overpressure peak attenuation is minimal. As the distance between the explosion center and the interior of the tunnel increases, all parameters decline. Both experiments and simulations reveal a unique change in the time history of overpressure and shock wave parameters near the 9 m measurement point inside the tunnel. By analyzing pressure contour maps and overpressure time history, it is discovered that wavefront movement is the primary cause. Based on the fundamental shock wave theory, a higher overpressure peak of shock wave results in faster wavefront motion. Fro m the 3 m to 7 m section inside the entrance, the leading wavefront overpressure continuously attenuates with increasing distance, and its motion speed significantly decreases. However, the overpressure values of subsequent reflected waves attenuate more slowly or even exceed those of the leading wavefront due to continuous collision and superposition. Between the 7 m and 9 m sections inside the entrance, the reflected waves formed by later superposition catch up with and overlap the leading wavefront, resulting in an increase in the first peak value with increasing distance. This process is also clearly understood through the simulated overpressure contour map. Based on the experimental and numerical simulation results, a predictive model for shock wave overpressure within the channel, which has practical engineering reference significance, has been developed.
To investigate the propagation process of shock waves within a channel under different explosive yields and charge positions, this study established an experimental channel designed for individual soldier transit. Through experiments and simulations, it is found that the quantity and position of the charge affect the time history of overpressure and shock wave parameters. Within the tunnel, the propagation velocity and overpressure peak of the shock wave decreased with increasing of distance, while the duration and impulse of positive overpressure continuously extend and increase. When the charge equivalent increases, all shock wave parameters are enhanced, though the influence on the rate of overpressure peak attenuation is minimal. As the distance between the explosion center and the interior of the tunnel increases, all parameters decline. Both experiments and simulations reveal a unique change in the time history of overpressure and shock wave parameters near the 9 m measurement point inside the tunnel. By analyzing pressure contour maps and overpressure time history, it is discovered that wavefront movement is the primary cause. Based on the fundamental shock wave theory, a higher overpressure peak of shock wave results in faster wavefront motion. Fro m the 3 m to 7 m section inside the entrance, the leading wavefront overpressure continuously attenuates with increasing distance, and its motion speed significantly decreases. However, the overpressure values of subsequent reflected waves attenuate more slowly or even exceed those of the leading wavefront due to continuous collision and superposition. Between the 7 m and 9 m sections inside the entrance, the reflected waves formed by later superposition catch up with and overlap the leading wavefront, resulting in an increase in the first peak value with increasing distance. This process is also clearly understood through the simulated overpressure contour map. Based on the experimental and numerical simulation results, a predictive model for shock wave overpressure within the channel, which has practical engineering reference significance, has been developed.
, Available online , doi: 10.11883/bzycj-2024-0283
Abstract:
Steel-concrete-steel composite (SCS) wall has been applied in high-rise buildings and nuclear power plants. Its performance under accidental and extreme loads during the whole life cycle deserves attention. Considering that fires and explosions often occur simultaneously, and that the mechanical properties of steel and concrete are deteriorated significantly at high temperatures, this leads to serious degradation of blast resistance of structural members. In this context, a total of 120 finite element (FE) models of SCS walls under combined fire and explosion were established using ABAQUS software. First, the FE models were verified based on existing fire resistance tests and explosion tests at room temperature on SCS walls. Then, the blast resistance mechanism of SCS walls was analyzed, and the influences of key parameters, including fire duration, explosion charge, steel plate ratio, material strength, tie bars spacing and axial compression ratio, on the explosion resistance were investigated. Finally, based on the single-degree of freedom method, the formulas were proposed to predict the maximum deformation of SCS walls under combined fire exposure and explosion. The results show that SCS walls primarily exhibit overall bending failure under coupled fire exposure and explosion. With the increase of fire duration, the contribution of the steel plate on the fire-exposed side to the energy dissipation decreases, and the plastic deformation of the steel plate on the non-fire-exposed side gradually becomes the main energy dissipation component. Fire duration, explosion charge and steel strength significantly affect the blast resistance of SCS walls under fire conditions. When exposed to fire for 90 minutes, the maximum mid-span deformation decreases by approximately 22%, as the steel yield strength increases from 235MPa to 460MPa. However, the influence of the concrete strength is minor. The maximum deformation of SCS walls can be reasonably predicted by the proposed formulas based on the single-degree of freedom method under coupled fire exposure and explosion.
Steel-concrete-steel composite (SCS) wall has been applied in high-rise buildings and nuclear power plants. Its performance under accidental and extreme loads during the whole life cycle deserves attention. Considering that fires and explosions often occur simultaneously, and that the mechanical properties of steel and concrete are deteriorated significantly at high temperatures, this leads to serious degradation of blast resistance of structural members. In this context, a total of 120 finite element (FE) models of SCS walls under combined fire and explosion were established using ABAQUS software. First, the FE models were verified based on existing fire resistance tests and explosion tests at room temperature on SCS walls. Then, the blast resistance mechanism of SCS walls was analyzed, and the influences of key parameters, including fire duration, explosion charge, steel plate ratio, material strength, tie bars spacing and axial compression ratio, on the explosion resistance were investigated. Finally, based on the single-degree of freedom method, the formulas were proposed to predict the maximum deformation of SCS walls under combined fire exposure and explosion. The results show that SCS walls primarily exhibit overall bending failure under coupled fire exposure and explosion. With the increase of fire duration, the contribution of the steel plate on the fire-exposed side to the energy dissipation decreases, and the plastic deformation of the steel plate on the non-fire-exposed side gradually becomes the main energy dissipation component. Fire duration, explosion charge and steel strength significantly affect the blast resistance of SCS walls under fire conditions. When exposed to fire for 90 minutes, the maximum mid-span deformation decreases by approximately 22%, as the steel yield strength increases from 235MPa to 460MPa. However, the influence of the concrete strength is minor. The maximum deformation of SCS walls can be reasonably predicted by the proposed formulas based on the single-degree of freedom method under coupled fire exposure and explosion.
, Available online , doi: 10.11883/bzycj-2024-0350
Abstract:
In blast-resistant structural design for conventional weapons, previous studies on blast-induced stress waves in solid media have predominantly focused on soil and rock media (i.e., ground shock issues), whereas research on the propagation and attenuation laws of stress waves in concrete remains relatively limited. Based on the KCC constitutive model in conjunction with the multi-material ALE (MMALE) algorithm, the propagation laws of stress waves in concrete induced by cylindrical charge explosion were numerically investigated. Firstly, the applicability of the constitutive model parameters and numerical algorithm were validated by comparing the results with the existing experiments. Subsequently, the peak stress was employed as a criterion to delineate the explosive damage zones in the concrete surrounding the charge. Additionally, the attenuation laws of explosion stress waves in each damage zone were discussed. Finally, the effect of burial depth was taken into further considered, and a formula for calculating the peak stress in concrete induced by cylindrical charge explosion was established. It was found that the attenuation patterns of blast-induced stress waves differ significantly in each explosion failure zone. The stress waves in the near-field zone (quasi-fluid and crushing zones) demonstrates a more rapid attenuation rate compared to that in the mid-field zone (transition and fracture zones). Furthermore, an increase in the aspect ratio of the cylindrical charge leads to an acceleration in the attenuation of the normal peak stress. Moreover, the established formula for calculating the peak stress of blast-induced stress waves enables accurate and rapid determination of the normal peak stress generated by cylindrical charges with varying geometries and burial depths, which can be served as a valuable reference for blast-resistant design of concrete structures.
In blast-resistant structural design for conventional weapons, previous studies on blast-induced stress waves in solid media have predominantly focused on soil and rock media (i.e., ground shock issues), whereas research on the propagation and attenuation laws of stress waves in concrete remains relatively limited. Based on the KCC constitutive model in conjunction with the multi-material ALE (MMALE) algorithm, the propagation laws of stress waves in concrete induced by cylindrical charge explosion were numerically investigated. Firstly, the applicability of the constitutive model parameters and numerical algorithm were validated by comparing the results with the existing experiments. Subsequently, the peak stress was employed as a criterion to delineate the explosive damage zones in the concrete surrounding the charge. Additionally, the attenuation laws of explosion stress waves in each damage zone were discussed. Finally, the effect of burial depth was taken into further considered, and a formula for calculating the peak stress in concrete induced by cylindrical charge explosion was established. It was found that the attenuation patterns of blast-induced stress waves differ significantly in each explosion failure zone. The stress waves in the near-field zone (quasi-fluid and crushing zones) demonstrates a more rapid attenuation rate compared to that in the mid-field zone (transition and fracture zones). Furthermore, an increase in the aspect ratio of the cylindrical charge leads to an acceleration in the attenuation of the normal peak stress. Moreover, the established formula for calculating the peak stress of blast-induced stress waves enables accurate and rapid determination of the normal peak stress generated by cylindrical charges with varying geometries and burial depths, which can be served as a valuable reference for blast-resistant design of concrete structures.
, 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.
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-2024-0431
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-2024-0361
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-2024-0203
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-2024-0279
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.
