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2025,
45(9):
091001.
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.
2025,
45(9):
092101.
doi: 10.11883/bzycj-2024-0356
Abstract:
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.
2025,
45(9):
092102.
doi: 10.11883/bzycj-2024-0300
Abstract:
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.
2025,
45(9):
092201.
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. From 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. From 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.
2025,
45(9):
092202.
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 Karagozian and Case concrete (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 Karagozian and Case concrete (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.
2025,
45(9):
092301.
doi: 10.11883/bzycj-2024-0333
Abstract:
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.
2025,
45(9):
093101.
doi: 10.11883/bzycj-2024-0309
Abstract:
This study investigates the 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, 1.25–2.50 mm, 0.60–1.25 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 four stages: elastic, yielding, plastic and unloading. 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 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, 1.25–2.50 mm, 0.60–1.25 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 four stages: elastic, yielding, plastic and unloading. 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.
2025,
45(9):
093102.
doi: 10.11883/bzycj-2024-0385
Abstract:
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.
2025,
45(9):
093301.
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.
2025,
45(9):
093401.
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.
2025,
45(9):
095101.
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 China 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 China 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.
2025,
45(9):
095201.
doi: 10.11883/bzycj-2024-0365
Abstract:
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.
2025,
45(9):
095401.
doi: 10.11883/bzycj-2024-0268
Abstract:
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.
