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, Available online , doi: 10.11883/bzycj-2025-0092
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Contact explosion is an important condition in the damage and protection of underwater structures, and the pulsating bubbles generated by explosive underwater explosion are an important damage source. The current research on underwater explosion bubbles mainly focuses on the pulsating characteristics of spherical bubbles under free-field and typical boundary conditions, while there is a notable lack of research on non-spherical bubbles under contact explosion conditions. The pulsation characteristics of underwater contact explosion bubbles were systematically investigated through theoretical modeling, numerical simulations, and experiments. To address the theoretical gap in contact explosion dynamics, a hemispherical bubble dynamics model under rigid wall contact conditions was established based on incompressible and inviscid fluid assumptions. By comparing present model with the spherical bubble pulsation model in an incompressible flow field, quantitative relationships between parameters such as the maximum bubble radius, initial radius, pulsation period were obtained. Theoretical analysis reveals that the maximum radius, initial radius, and pulsation period of contact explosion bubbles are 1.26 (theoretical scaling factor) times those of free-field conditions. An error analysis was conducted to account for factors such as fluid compressibility, unstable bubble deformation, and energy dissipation induced by bubble-rigid wall interactions. Numerical simulations using LS-DYNA for underwater explosions with 0.3 g, 0.233 g, and 5 g TNT charges under varying water depths reveal that the scaling factors for maximum radius and pulsation period under contact explosion conditions range from 1.22 to 1.24 and 1.20 to 1.21 times those of free-field results, respectively, with simulation errors below 5% compared to theoretical predictions. Experimental validation in a water tank shows that the maximum radius and period of contact explosion bubbles are 1.10 and 1.06 times those of free-field conditions. During the experiments, plate vibrations were observed upon explosion, which significantly contributed to experimental errors. This work addresses the theoretical gap in contact explosion bubble dynamics, enhances the understanding of boundary effects in underwater explosion phenomena.
Contact explosion is an important condition in the damage and protection of underwater structures, and the pulsating bubbles generated by explosive underwater explosion are an important damage source. The current research on underwater explosion bubbles mainly focuses on the pulsating characteristics of spherical bubbles under free-field and typical boundary conditions, while there is a notable lack of research on non-spherical bubbles under contact explosion conditions. The pulsation characteristics of underwater contact explosion bubbles were systematically investigated through theoretical modeling, numerical simulations, and experiments. To address the theoretical gap in contact explosion dynamics, a hemispherical bubble dynamics model under rigid wall contact conditions was established based on incompressible and inviscid fluid assumptions. By comparing present model with the spherical bubble pulsation model in an incompressible flow field, quantitative relationships between parameters such as the maximum bubble radius, initial radius, pulsation period were obtained. Theoretical analysis reveals that the maximum radius, initial radius, and pulsation period of contact explosion bubbles are 1.26 (theoretical scaling factor) times those of free-field conditions. An error analysis was conducted to account for factors such as fluid compressibility, unstable bubble deformation, and energy dissipation induced by bubble-rigid wall interactions. Numerical simulations using LS-DYNA for underwater explosions with 0.3 g, 0.233 g, and 5 g TNT charges under varying water depths reveal that the scaling factors for maximum radius and pulsation period under contact explosion conditions range from 1.22 to 1.24 and 1.20 to 1.21 times those of free-field results, respectively, with simulation errors below 5% compared to theoretical predictions. Experimental validation in a water tank shows that the maximum radius and period of contact explosion bubbles are 1.10 and 1.06 times those of free-field conditions. During the experiments, plate vibrations were observed upon explosion, which significantly contributed to experimental errors. This work addresses the theoretical gap in contact explosion bubble dynamics, enhances the understanding of boundary effects in underwater explosion phenomena.
, Available online , doi: 10.11883/bzycj-2024-0515
Abstract:
Underwater explosions in deep-sea environments involve complex interactions, making both theoretical modeling and experimental validation particularly challenging. While previous research has provided valuable insights into the basic features of shock wave propagation and bubble dynamics in underwater explosions, most existing studies are limited to shallow water scenarios or narrowly defined environmental parameters. Systematic research on the laws governing shock wave loads from deep-sea explosions and their associated bubble pulsation under varying operational conditions holds critical academic significance. Numerical simulations were conducted utilizing a zoned solution algorithm for shock waves derived from the unified equation for bubble dynamics theoretical model. The algorithm enabled numerical simulation of shock wave peak pressure and pressure attenuation processes under diverse initial conditions. Comparative analysis with experimental data confirmed model reliability, demonstrating a mere 0.5% deviation between simulated and measured peak pressures and excellent agreement in pressure attenuation processes. The simulations specifically investigated the influence of water depth, stand-off distance, and explosive charge mass on the peak pressure of the underwater explosion shock wave and explored the variation patterns of the shock wave under different initial conditions through an in-depth analysis of the shock wave impulse and specific shock wave energy. Furthermore, employing the same theoretical model, the bubble pulsation characteristics within a single cycle under varying water depths and explosive charge masses were comparatively analyzed. Traditional empirical formulas were employed to analyze the numerical simulation results, and dimensionless treatment was conducted on the parameters. The results reveal that the peak pressure of the shock wave is primarily influenced by the charge mass and stand-off distance, and increases with water depth at an approximate rate of 1% per kilometer. In contrast, both shock wave impulse and specific shock wave energy decrease with increasing water depth and stand-off distance, but show a positive correlation with charge magnitude. The bubble pulse radius is primarily determined by both the charge weight and the water depth, with the bubble pulsation phenomenon becoming attenuated in deep-water environments. Compared to the traditional Cole empirical formula, the simulated bubble pulse radius is reduced in the range of 0.1 to 10 km. The simulation indicates an asymmetry in the pulsation cycle: the expansion phase consistently lasts slightly longer than the collapse phase. These findings contribute to a more nuanced understanding of underwater explosion phenomena in deep-sea environments and have practical implications for naval engineering, subsea structural safety assessment, and explosive ordnance disposal in complex oceanic settings.
Underwater explosions in deep-sea environments involve complex interactions, making both theoretical modeling and experimental validation particularly challenging. While previous research has provided valuable insights into the basic features of shock wave propagation and bubble dynamics in underwater explosions, most existing studies are limited to shallow water scenarios or narrowly defined environmental parameters. Systematic research on the laws governing shock wave loads from deep-sea explosions and their associated bubble pulsation under varying operational conditions holds critical academic significance. Numerical simulations were conducted utilizing a zoned solution algorithm for shock waves derived from the unified equation for bubble dynamics theoretical model. The algorithm enabled numerical simulation of shock wave peak pressure and pressure attenuation processes under diverse initial conditions. Comparative analysis with experimental data confirmed model reliability, demonstrating a mere 0.5% deviation between simulated and measured peak pressures and excellent agreement in pressure attenuation processes. The simulations specifically investigated the influence of water depth, stand-off distance, and explosive charge mass on the peak pressure of the underwater explosion shock wave and explored the variation patterns of the shock wave under different initial conditions through an in-depth analysis of the shock wave impulse and specific shock wave energy. Furthermore, employing the same theoretical model, the bubble pulsation characteristics within a single cycle under varying water depths and explosive charge masses were comparatively analyzed. Traditional empirical formulas were employed to analyze the numerical simulation results, and dimensionless treatment was conducted on the parameters. The results reveal that the peak pressure of the shock wave is primarily influenced by the charge mass and stand-off distance, and increases with water depth at an approximate rate of 1% per kilometer. In contrast, both shock wave impulse and specific shock wave energy decrease with increasing water depth and stand-off distance, but show a positive correlation with charge magnitude. The bubble pulse radius is primarily determined by both the charge weight and the water depth, with the bubble pulsation phenomenon becoming attenuated in deep-water environments. Compared to the traditional Cole empirical formula, the simulated bubble pulse radius is reduced in the range of 0.1 to 10 km. The simulation indicates an asymmetry in the pulsation cycle: the expansion phase consistently lasts slightly longer than the collapse phase. These findings contribute to a more nuanced understanding of underwater explosion phenomena in deep-sea environments and have practical implications for naval engineering, subsea structural safety assessment, and explosive ordnance disposal in complex oceanic settings.
, Available online , doi: 10.11883/bzycj-2025-0027
Abstract:
The quasi-static pressure thermodynamic model for confined explosions provides an effective characterization of pressure evolution with mass-to-volume ratio m/V, and derivation of physical quantities such as gas adiabatic index from products and temperature. However, the thermodynamic model based on detonation and combustion equations that neglects reaction equilibrium demonstrates growing deviations from the quasi-static pressure curve in UFC 3-340-02 blast-resistant design standard after carbon precipitates in detonation products, and existing research inadequately addresses the necessity of incorporating reaction equilibrium for various physical quantities in TNT confined explosion thermodynamic models. In order to investigate the influence of reaction equilibrium on thermodynamic calculation results, the model neglecting reaction equilibrium was modified based on the energy conservation equation of isochoric processes and the solid carbon precipitation phenomenon. The modified model has a consistency with the UFC curve for m/V≥0.371 kg/m3. Then, a comparative analysis was conducted on the results of thermodynamic models considering and not considering the reaction equilibrium based on the unified solution framework. The results indicate that incorporating chemical equilibrium into quasi-static pressure calculation introduces a maximum relative deviation below 20%, and critical thresholds alters, i.e., the m/V for carbon precipitation shifts from 0.371 to 3.850 kg/m3, and peak temperature transitions from 0.371 to 0.680 kg/m3. Significant divergence in mole numbers of product composition emerges progressively when m/V exceeds 0.1 kg/m3. Therefore, the reaction equilibrium-based thermodynamic model is a more rational choice for calculating quantities related to components and temperature in TNT confined explosions with m/V>0.1 kg/m3. Finally, a simplified calculation method for products, temperature, and pressure during the quasi-static phase of TNT confined explosions considering reaction equilibrium is proposed based on symbolic regression algorithm. The research contributes to a theoretical understanding of equilibrium effects on thermodynamic model results and the practical implementation of rapid parameter estimation in TNT confined explosion scenarios.
The quasi-static pressure thermodynamic model for confined explosions provides an effective characterization of pressure evolution with mass-to-volume ratio m/V, and derivation of physical quantities such as gas adiabatic index from products and temperature. However, the thermodynamic model based on detonation and combustion equations that neglects reaction equilibrium demonstrates growing deviations from the quasi-static pressure curve in UFC 3-340-02 blast-resistant design standard after carbon precipitates in detonation products, and existing research inadequately addresses the necessity of incorporating reaction equilibrium for various physical quantities in TNT confined explosion thermodynamic models. In order to investigate the influence of reaction equilibrium on thermodynamic calculation results, the model neglecting reaction equilibrium was modified based on the energy conservation equation of isochoric processes and the solid carbon precipitation phenomenon. The modified model has a consistency with the UFC curve for m/V≥0.371 kg/m3. Then, a comparative analysis was conducted on the results of thermodynamic models considering and not considering the reaction equilibrium based on the unified solution framework. The results indicate that incorporating chemical equilibrium into quasi-static pressure calculation introduces a maximum relative deviation below 20%, and critical thresholds alters, i.e., the m/V for carbon precipitation shifts from 0.371 to 3.850 kg/m3, and peak temperature transitions from 0.371 to 0.680 kg/m3. Significant divergence in mole numbers of product composition emerges progressively when m/V exceeds 0.1 kg/m3. Therefore, the reaction equilibrium-based thermodynamic model is a more rational choice for calculating quantities related to components and temperature in TNT confined explosions with m/V>0.1 kg/m3. Finally, a simplified calculation method for products, temperature, and pressure during the quasi-static phase of TNT confined explosions considering reaction equilibrium is proposed based on symbolic regression algorithm. The research contributes to a theoretical understanding of equilibrium effects on thermodynamic model results and the practical implementation of rapid parameter estimation in TNT confined explosion scenarios.
, Available online , doi: 10.11883/bzycj-2024-0455
Abstract:
To select the shaped charge structure suitable for large-distance non-contact penetration damage in water, three typical shaped-charge structures, explosively formed projectile (EFP), jetting projectile charge (JPC), and shaped charge jet (SCJ), were selected. The velocity tests of different penetrators before entering water, before hitting the target, and after penetrating the target were carried out, and the penetration tests of double-layer spaced targets in water were conducted. Firstly, a comparative test of penetration of three types of shaped charges in the air was carried out to verify the rationality of the structure of shaped charges. The air explosion height of 35 cm was selected to meet the penetration requirements of the three shaped charges. At the same time, the velocity of the shaped charges before penetrating water was measured, which provides the basis for the underwater penetration test. Secondly, the penetration test of three types of shaped charges on an underwater double-layer spaced target was carried out when the air height was 35 cm, and the length of the water medium in front of the target was 20 cm, 45 cm, and 100 cm. The reflected pressures were measured by the wall pressure sensor and PVDF sensor. The velocities of the penetrator at the time of water entry, before the target, and after the target were measured by double-layer on-off net targets.The damage performance of three shaped charge structures on the double-layer spaced target plate was respectively obtained when the water medium in front of the target was at short range, medium range and long range.Based on the projectile-target structure used in the experiment, a two-dimensional finite element model of shaped charge penetrating a double-layer spaced target in water was established using ANSYS/LS-DYNA finite element software. The measured velocity values of the shaped charge penetrator before entering the water, before hitting the target, and after passing through the target were compared with the numerical simulation results to verify the accuracy of the model. The error rate is about 3 %. Based on the verified finite element model, the time series characteristics of the underwater damage element of the shaped charge, the peak characteristics of the forward shock wave in the water, the variation law of the penetration velocity in the water, and the penetration performance of the shaped charge against the double-layer spaced target in the water were studied. The results show that the forward shock wave reaches the target plate before the penetrator. As the length of the water medium increases, the peak pressure of the forward shock wave at the front target plate decreases linearly, and the peak pressure of the forward shock wave at the rear target plate decreases nonlinearly. The velocities of EFP, JPC, and SCJ decrease nonlinearly with the increase of water medium, and the velocity in front of the SCJ target is about twice that of JPC.When the length of the water medium in front of the target is not more than 25 cm, the maximum perforation diameter formed by EFP on the front target plate reaches 5 cm, which is 1.3 times the perforation diameter of JPC and 3 times the perforation diameter of SCJ. When the length of the water medium in front of the target is not more than 100 cm, JPC and SCJ have better penetration effect on the double-layer spacer target, and the penetration performance of JPC is better than that of SCJ.
To select the shaped charge structure suitable for large-distance non-contact penetration damage in water, three typical shaped-charge structures, explosively formed projectile (EFP), jetting projectile charge (JPC), and shaped charge jet (SCJ), were selected. The velocity tests of different penetrators before entering water, before hitting the target, and after penetrating the target were carried out, and the penetration tests of double-layer spaced targets in water were conducted. Firstly, a comparative test of penetration of three types of shaped charges in the air was carried out to verify the rationality of the structure of shaped charges. The air explosion height of 35 cm was selected to meet the penetration requirements of the three shaped charges. At the same time, the velocity of the shaped charges before penetrating water was measured, which provides the basis for the underwater penetration test. Secondly, the penetration test of three types of shaped charges on an underwater double-layer spaced target was carried out when the air height was 35 cm, and the length of the water medium in front of the target was 20 cm, 45 cm, and 100 cm. The reflected pressures were measured by the wall pressure sensor and PVDF sensor. The velocities of the penetrator at the time of water entry, before the target, and after the target were measured by double-layer on-off net targets.The damage performance of three shaped charge structures on the double-layer spaced target plate was respectively obtained when the water medium in front of the target was at short range, medium range and long range.Based on the projectile-target structure used in the experiment, a two-dimensional finite element model of shaped charge penetrating a double-layer spaced target in water was established using ANSYS/LS-DYNA finite element software. The measured velocity values of the shaped charge penetrator before entering the water, before hitting the target, and after passing through the target were compared with the numerical simulation results to verify the accuracy of the model. The error rate is about 3 %. Based on the verified finite element model, the time series characteristics of the underwater damage element of the shaped charge, the peak characteristics of the forward shock wave in the water, the variation law of the penetration velocity in the water, and the penetration performance of the shaped charge against the double-layer spaced target in the water were studied. The results show that the forward shock wave reaches the target plate before the penetrator. As the length of the water medium increases, the peak pressure of the forward shock wave at the front target plate decreases linearly, and the peak pressure of the forward shock wave at the rear target plate decreases nonlinearly. The velocities of EFP, JPC, and SCJ decrease nonlinearly with the increase of water medium, and the velocity in front of the SCJ target is about twice that of JPC.When the length of the water medium in front of the target is not more than 25 cm, the maximum perforation diameter formed by EFP on the front target plate reaches 5 cm, which is 1.3 times the perforation diameter of JPC and 3 times the perforation diameter of SCJ. When the length of the water medium in front of the target is not more than 100 cm, JPC and SCJ have better penetration effect on the double-layer spacer target, and the penetration performance of JPC is better than that of SCJ.
, Available online , doi: 10.11883/bzycj-2024-0497
Abstract:
Layered composite rock masses are widely found in mining, tunnel excavation, and slope stabilization engineering, representing a common geological structure in nature. Due to their formation conditions, the internal strength of layered composite rock masses often exhibits gradient variations. This study simulates layered composite rock masses using epoxy resin materials and employs a dynamic photoelasticity-digital image correlation integrated experimental system to conduct a visualized, detailed analysis of the propagation process of explosive stress waves in gradient media. to investigate the attenuation patterns and energy flux density evolution of explosive stress waves under both forward and reverse gradient conditions. By comparing the dynamic photoelastic stripe patterns, the study visually analyzes the transmission and reflection characteristics under different propagation paths, and uses digital image correlation to quantitatively assess the differences in the attenuation rates of explosive stress waves. The results indicate that the fringe order of the explosive stress wave remains unchanged in the forward propagation path, with significant reflection at the joint surface. In the reverse propagation path, the fringe order exhibits a decaying pattern, and the dynamic photoelastic fringes maintain good continuity at the joint surface. The explosive stress wave demonstrates better penetration in reverse gradient media. Changes in joints and materials within gradient media alter the rate of horizontal stress attenuation, with faster attenuation observed in positive gradient media. By introducing the Poynting vector to compare energy flux density, it was found that energy flux density decays faster in positive gradient materials at the same measurement points, and the propagation of explosive stress waves in positive gradient materials exhibits an “energy-absorbing” process.
Layered composite rock masses are widely found in mining, tunnel excavation, and slope stabilization engineering, representing a common geological structure in nature. Due to their formation conditions, the internal strength of layered composite rock masses often exhibits gradient variations. This study simulates layered composite rock masses using epoxy resin materials and employs a dynamic photoelasticity-digital image correlation integrated experimental system to conduct a visualized, detailed analysis of the propagation process of explosive stress waves in gradient media. to investigate the attenuation patterns and energy flux density evolution of explosive stress waves under both forward and reverse gradient conditions. By comparing the dynamic photoelastic stripe patterns, the study visually analyzes the transmission and reflection characteristics under different propagation paths, and uses digital image correlation to quantitatively assess the differences in the attenuation rates of explosive stress waves. The results indicate that the fringe order of the explosive stress wave remains unchanged in the forward propagation path, with significant reflection at the joint surface. In the reverse propagation path, the fringe order exhibits a decaying pattern, and the dynamic photoelastic fringes maintain good continuity at the joint surface. The explosive stress wave demonstrates better penetration in reverse gradient media. Changes in joints and materials within gradient media alter the rate of horizontal stress attenuation, with faster attenuation observed in positive gradient media. By introducing the Poynting vector to compare energy flux density, it was found that energy flux density decays faster in positive gradient materials at the same measurement points, and the propagation of explosive stress waves in positive gradient materials exhibits an “energy-absorbing” process.
, Available online , doi: 10.11883/bzycj-2024-0520
Abstract:
Significant structural and layout disparities exist between the blended wing body (BWB) civil aircraft and conventional cylindrical fuselage metal aircraft. These differences render the impact resistance characteristics of the non-circular fuselage structure and the injury mechanisms for occupants unclear. To address this, a 460-seat BWB aircraft model was developed based on the pultruded rod stitched efficient unitized structure (PRSEUS) proposed by the National Aeronautics and Space Administration (NASA). The aircraft features a wingspan of 80 meters, a range of approximately 16,000 km, a cruising Mach number of 0.85, and a cruising altitude of 11 000 m. Three typical loading conditions were employed to evaluate the strength and stiffness of the BWB structure: critical maneuvering loads (2.5g positive overload and −1.0g negative overload) and cabin pressurization loads (double the cabin pressurization load). Through iterative structural design optimization, the model was confirmed to meet these typical loading requirements while demonstrating sufficient safety margins. The model incorporated all major structural components of the BWB configuration, including skin, frames, stringers, cargo floor, cabin floor, support columns, and fuselage ribs. In the finite element modeling process, elements with minimal influence on the crash response were reasonably simplified to reduce computational complexity. For instance, the outer wings and engines were simplified as concentrated mass points, and the cabin seats and passengers were modeled as concentrated masses fixed to the seat rails. The primary structural components, such as the skin, stringers, floor, and floor beams, were constructed from AS4 carbon fiber composite laminates and modeled using shell elements. The pultruded rods were made of AS4 carbon fiber composite and modeled using beam elements. The foam core of the frames and fuselage ribs were made of Rohacell-110-WF foam material and modeled using solid elements. The remaining structures were made of7075 aluminum alloy and modeled using shell elements. The final model had a total mass of 162.87 tons and consisted of 2 679 991 elements. Five vertical impact velocities ranging from 7.92 to 9.14 m/s were selected to analyze the cabin space integrity, acceleration response of the cabin floor, and the impact characteristics of the primary load-bearing structures. The results indicate that the cabin area of the lift-body fuselage remains largely intact under the different impact velocities. The primary damage occurs below the cabin floor, with compressive damage concentrated in the lower structures of the middle and aft fuselage. The survivable space is preserved. Compared to a round-section fuselage, the deformation of the BWB frames is relatively small, and upward bulging is not significant, making it challenging to form effective plastic hinges. During the crash, the acceleration load distribution of the blended wing body-integrated aircraft exhibits a decreasing trend from the central aisle to the sides of the fuselage, with peak acceleration loads being higher at the central aisle. Under all five crash conditions, passenger injury levels at various cabin positions fall within the serious but acceptable and safe regions. Regarding structural energy absorption, the frames are identified as the primary energy-absorbing structures, followed by the fuselage ribs. However, the cargo pillars do not effectively crush and absorb energy. For future crashworthiness design of BWB civil aircraft, the cargo structure should be a key consideration.
Significant structural and layout disparities exist between the blended wing body (BWB) civil aircraft and conventional cylindrical fuselage metal aircraft. These differences render the impact resistance characteristics of the non-circular fuselage structure and the injury mechanisms for occupants unclear. To address this, a 460-seat BWB aircraft model was developed based on the pultruded rod stitched efficient unitized structure (PRSEUS) proposed by the National Aeronautics and Space Administration (NASA). The aircraft features a wingspan of 80 meters, a range of approximately 16,000 km, a cruising Mach number of 0.85, and a cruising altitude of 11 000 m. Three typical loading conditions were employed to evaluate the strength and stiffness of the BWB structure: critical maneuvering loads (2.5g positive overload and −1.0g negative overload) and cabin pressurization loads (double the cabin pressurization load). Through iterative structural design optimization, the model was confirmed to meet these typical loading requirements while demonstrating sufficient safety margins. The model incorporated all major structural components of the BWB configuration, including skin, frames, stringers, cargo floor, cabin floor, support columns, and fuselage ribs. In the finite element modeling process, elements with minimal influence on the crash response were reasonably simplified to reduce computational complexity. For instance, the outer wings and engines were simplified as concentrated mass points, and the cabin seats and passengers were modeled as concentrated masses fixed to the seat rails. The primary structural components, such as the skin, stringers, floor, and floor beams, were constructed from AS4 carbon fiber composite laminates and modeled using shell elements. The pultruded rods were made of AS4 carbon fiber composite and modeled using beam elements. The foam core of the frames and fuselage ribs were made of Rohacell-110-WF foam material and modeled using solid elements. The remaining structures were made of
, Available online , doi: 10.11883/bzycj-2024-0332
Abstract:
To investigate the damage mechanism and load characteristics of caisson wharf under underwater contact and near-field explosion, a high-fidelity numerical model was conducted based on the scaled model tests of caisson wharf and verified by comparing the simulation results with the experimental data. The propagation and attenuation characteristics of shock waves inside the caisson, partition walls, and internal backfill soil were analyzed. The destruction process and typical damage mechanisms of the caisson wharf were analyzed by comparing Holmquist‒Johnson‒Cook constitutive model damage contour maps with experimental results. The results shows that the damage areas and characteristics of the caisson wharf are largely consistent under both underwater contact and near-field explosion. The primary damage areas are blast-facing wall and deck slab. The blast-facing wall exhibits cratering and breaching phenomena, while of the deck slab shows transverse full-length cracks at trench-slab connections, longitudinal cracks, and blow-off. The side walls and internal partitions of the caisson wharf sustain relatively minor damage. Shock wave within the caisson subjected to underwater contact and near-field explosions undergo reflection and transmission at the interfaces between the partitions and fillings within the compartments. The blast-facing wall and side walls of the wharf are subjected to shock loads. The transmitted compressive waves across the transverse bulkheads and blast-resistant back walls exhibited amplification compared to the incident waves, whereas attenuation was observed as the waves traversed the sand-filled compartments. Numerical simulation results revealed that the shock wave load within the caisson undergoes a decay rate that transitions from rapid to gradual. Damage characteristics of caisson wharf is primarily shaped during the underwater explosion shockwave phase. Neglecting large-scale macroscopic movements such as uplift and scattering post panel failure, the damage formation time slightly exceeds twice the shockwave propagation duration through the structure.
To investigate the damage mechanism and load characteristics of caisson wharf under underwater contact and near-field explosion, a high-fidelity numerical model was conducted based on the scaled model tests of caisson wharf and verified by comparing the simulation results with the experimental data. The propagation and attenuation characteristics of shock waves inside the caisson, partition walls, and internal backfill soil were analyzed. The destruction process and typical damage mechanisms of the caisson wharf were analyzed by comparing Holmquist‒Johnson‒Cook constitutive model damage contour maps with experimental results. The results shows that the damage areas and characteristics of the caisson wharf are largely consistent under both underwater contact and near-field explosion. The primary damage areas are blast-facing wall and deck slab. The blast-facing wall exhibits cratering and breaching phenomena, while of the deck slab shows transverse full-length cracks at trench-slab connections, longitudinal cracks, and blow-off. The side walls and internal partitions of the caisson wharf sustain relatively minor damage. Shock wave within the caisson subjected to underwater contact and near-field explosions undergo reflection and transmission at the interfaces between the partitions and fillings within the compartments. The blast-facing wall and side walls of the wharf are subjected to shock loads. The transmitted compressive waves across the transverse bulkheads and blast-resistant back walls exhibited amplification compared to the incident waves, whereas attenuation was observed as the waves traversed the sand-filled compartments. Numerical simulation results revealed that the shock wave load within the caisson undergoes a decay rate that transitions from rapid to gradual. Damage characteristics of caisson wharf is primarily shaped during the underwater explosion shockwave phase. Neglecting large-scale macroscopic movements such as uplift and scattering post panel failure, the damage formation time slightly exceeds twice the shockwave propagation duration through the structure.
, Available online , doi: 10.11883/bzycj-2024-0471
Abstract:
To accurately predict the explosion power fields in buildings, solving the failure of traditional empirical formulas often failing to account for complex environmental factor due to their inability to account for complex environmental factors, and that of numerical simulations inefficient for large-scale urban scenarios and do not meet the needs of rapid damage assessment. Addressing this challenge, an innovative prediction model for explosion power fields based on Graph Neural Networks (GNN) was constructed using an end-to-end strategy. This model enabled rapid and precise forecasting of three-dimensional physical fields, including peak overpressure, peak impulse, and shock-wave arrival times on building surfaces. Compared to numerical simulations, the proposed GNN model demonstrated excellent predictive performance: it achieved a mean square error of 0.97% for predicting surface overpressure parameters of single buildings with varying geometries, and an average prediction error of 3.17% for complex geometric buildings and building communities. When applied to real-world urban settings, the model maintains an average prediction error of 1.29%, completing individual physical field predictions in under 0.6 seconds—three to four orders of magnitude faster than numerical simulations. Furthermore, the model's high-precision predictions allow for the reconstruction of overpressure time history curves at any building surface location and the accurate assessment of structural damage. The proposed GNN model offers a novel approach for rapidly and accurately predicting explosion power fields in urban buildings during blast events. This advancement significantly enhances the capabilities for explosion damage assessment and anti-explosion design in ultra-large-scale complex engineering scenarios, providing substantial engineering value.
To accurately predict the explosion power fields in buildings, solving the failure of traditional empirical formulas often failing to account for complex environmental factor due to their inability to account for complex environmental factors, and that of numerical simulations inefficient for large-scale urban scenarios and do not meet the needs of rapid damage assessment. Addressing this challenge, an innovative prediction model for explosion power fields based on Graph Neural Networks (GNN) was constructed using an end-to-end strategy. This model enabled rapid and precise forecasting of three-dimensional physical fields, including peak overpressure, peak impulse, and shock-wave arrival times on building surfaces. Compared to numerical simulations, the proposed GNN model demonstrated excellent predictive performance: it achieved a mean square error of 0.97% for predicting surface overpressure parameters of single buildings with varying geometries, and an average prediction error of 3.17% for complex geometric buildings and building communities. When applied to real-world urban settings, the model maintains an average prediction error of 1.29%, completing individual physical field predictions in under 0.6 seconds—three to four orders of magnitude faster than numerical simulations. Furthermore, the model's high-precision predictions allow for the reconstruction of overpressure time history curves at any building surface location and the accurate assessment of structural damage. The proposed GNN model offers a novel approach for rapidly and accurately predicting explosion power fields in urban buildings during blast events. This advancement significantly enhances the capabilities for explosion damage assessment and anti-explosion design in ultra-large-scale complex engineering scenarios, providing substantial engineering value.
, Available online , doi: 10.11883/bzycj-2024-0435
Abstract:
During the underwater launch of multiple projectiles, each projectile operates within a highly complex and dynamic flow field, where its trajectory deflection is influenced by a combination of factors. These factors include initial conditions such as the projectile’s velocity and the presence of crossflow, as well as the mutual interference effects among the projectiles. To gain a deeper understanding of the cavitation evolution and trajectory interference characteristics during the underwater launch of multiple projectiles, this study develops a comprehensive numerical simulation model. The model integrates the overlapping grid technique and the finite volume method and is coupled with a six-degree-of-freedom(6-DOF) motion model. Through this model, the influence mechanisms of spatial arrangement, launch velocity, and crossflow on trajectory deflection are systematically analyzed. The results of this study reveal several important findings. First, the spatial arrangement of the projectiles has a relatively minor impact on trajectory deflection. An equilateral triangular configuration is found to be an optimal choice for practical applications, as it maximizes the efficient utilization of the launch space. Second, as the launch velocity increases, the wake interference between projectiles becomes more pronounced. This intensified interference leads to significant disturbances in the flow field and stronger mutual trajectory interference among the projectiles. Third, higher crossflow velocities exacerbate the asymmetric development of cavitation near the projectile shoulders. When the crossflow velocity exceeds 0.75 m/s, it becomes the dominant factor influencing trajectory deflection. These research findings provide a robust theoretical foundation for trajectory prediction and layout optimization in the underwater launch of multiple projectiles.
During the underwater launch of multiple projectiles, each projectile operates within a highly complex and dynamic flow field, where its trajectory deflection is influenced by a combination of factors. These factors include initial conditions such as the projectile’s velocity and the presence of crossflow, as well as the mutual interference effects among the projectiles. To gain a deeper understanding of the cavitation evolution and trajectory interference characteristics during the underwater launch of multiple projectiles, this study develops a comprehensive numerical simulation model. The model integrates the overlapping grid technique and the finite volume method and is coupled with a six-degree-of-freedom(6-DOF) motion model. Through this model, the influence mechanisms of spatial arrangement, launch velocity, and crossflow on trajectory deflection are systematically analyzed. The results of this study reveal several important findings. First, the spatial arrangement of the projectiles has a relatively minor impact on trajectory deflection. An equilateral triangular configuration is found to be an optimal choice for practical applications, as it maximizes the efficient utilization of the launch space. Second, as the launch velocity increases, the wake interference between projectiles becomes more pronounced. This intensified interference leads to significant disturbances in the flow field and stronger mutual trajectory interference among the projectiles. Third, higher crossflow velocities exacerbate the asymmetric development of cavitation near the projectile shoulders. When the crossflow velocity exceeds 0.75 m/s, it becomes the dominant factor influencing trajectory deflection. These research findings provide a robust theoretical foundation for trajectory prediction and layout optimization in the underwater launch of multiple projectiles.
, Available online , doi: 10.11883/bzycj-2024-0443
Abstract:
Supercritical CO2 phase transition rock-breaking is a dynamic destruction process under the combined action of shock waves and high-pressure gas. To deeply investigate the rock-breaking mechanisms of supercritical CO2 phase transition under multi-hole synchronous initiation and in-situ stress coupling conditions, targeting the actual working conditions of CO2 field rock-breaking, the initial rock-breaking pressure of a single hole was analyzed based on the thin-walled cylinder theory. A predictive model for the joint rock-breaking radius of multi-hole shock waves and high-pressure gas under in-situ stress was developed by integrating the one-dimensional detonation gas expansion theory. Field experiments on multi-hole CO2 phase transition rock-breaking were subsequently conducted for comparative validation. The results show that when the fracturing pipe is buried shallowly, the influence of in-situ stress on the stress distribution of the rock mass is relatively weak. When the pressure of a single hole is consistent, the more fracturing holes there are, the greater the superposed peak stress of each hole. In the direction perpendicular to the layout of the test hole, the peak stress of each hole shows a U-shaped parabolic distribution. The superposed stress of the fracturing holes at both ends is the largest. In the direction parallel to the layout of the test hole, the peak stress of each hole shows an inverted U-shaped parabolic distribution, and the superposed stress of the middle fracturing hole is the largest. In addition, the rock mass damage and fracture range under multi-pore impact obtained by acoustic wave testing in the field is in the shape of a three-dimensional funnel. The vertical damage and fracture range is between 5.05 and 5.73 m, and the planar damage and fracture range is between 4.3 and 5.6 m. The error between the measured value of the planar damage and fracture range and the theoretically calculated value is between 5.0% and 18.7%. The calculation error mainly comes from the uneven superposition stress of each fracturing hole. Further analysis shows that the radius of supercritical CO2 phase transition rock-breaking increases semi-parabolically with the superposed stress of the fracturing hole and increases logarithmically with the depth of the fracturing hole. As the compressive strength of the rock mass increases, the rock fracture toughness increases nearly linearly, and the corresponding rock-breaking radius decreases nearly linearly. The research results can provide a quantitative design basis for optimizing engineering parameters in the multi-pore supercritical CO2 phase transition for rock-breaking.
Supercritical CO2 phase transition rock-breaking is a dynamic destruction process under the combined action of shock waves and high-pressure gas. To deeply investigate the rock-breaking mechanisms of supercritical CO2 phase transition under multi-hole synchronous initiation and in-situ stress coupling conditions, targeting the actual working conditions of CO2 field rock-breaking, the initial rock-breaking pressure of a single hole was analyzed based on the thin-walled cylinder theory. A predictive model for the joint rock-breaking radius of multi-hole shock waves and high-pressure gas under in-situ stress was developed by integrating the one-dimensional detonation gas expansion theory. Field experiments on multi-hole CO2 phase transition rock-breaking were subsequently conducted for comparative validation. The results show that when the fracturing pipe is buried shallowly, the influence of in-situ stress on the stress distribution of the rock mass is relatively weak. When the pressure of a single hole is consistent, the more fracturing holes there are, the greater the superposed peak stress of each hole. In the direction perpendicular to the layout of the test hole, the peak stress of each hole shows a U-shaped parabolic distribution. The superposed stress of the fracturing holes at both ends is the largest. In the direction parallel to the layout of the test hole, the peak stress of each hole shows an inverted U-shaped parabolic distribution, and the superposed stress of the middle fracturing hole is the largest. In addition, the rock mass damage and fracture range under multi-pore impact obtained by acoustic wave testing in the field is in the shape of a three-dimensional funnel. The vertical damage and fracture range is between 5.05 and 5.73 m, and the planar damage and fracture range is between 4.3 and 5.6 m. The error between the measured value of the planar damage and fracture range and the theoretically calculated value is between 5.0% and 18.7%. The calculation error mainly comes from the uneven superposition stress of each fracturing hole. Further analysis shows that the radius of supercritical CO2 phase transition rock-breaking increases semi-parabolically with the superposed stress of the fracturing hole and increases logarithmically with the depth of the fracturing hole. As the compressive strength of the rock mass increases, the rock fracture toughness increases nearly linearly, and the corresponding rock-breaking radius decreases nearly linearly. The research results can provide a quantitative design basis for optimizing engineering parameters in the multi-pore supercritical CO2 phase transition for rock-breaking.
, Available online , doi: 10.11883/bzycj-2025-0154
Abstract:
Gas leakage and explosion accidents pose a serious threat to public safety. A critical prerequisite for accurately predicting the explosive effects of combustible gas leakage lies in determining the concentration distribution following the leakage. To develop a real-time, full-field spatiotemporal prediction model for combustible gas leakage and diffusion, and to achieve efficient prediction of the equivalent gas cloud volume, a novel graph neural network model based on a dual-neural-network architecture and a multi-stage training strategy, named multi-stage dual graph neural network (MSDGNN), was proposed. The MSDGNN model consists of two synergistic sub-networks: (1) a concentration network (Ncon), which establishes the mapping relationship between the concentration fields of two consecutive timesteps, and (2) a volume network (Nvol), which generates the equivalent gas cloud volume at each timestep to provide a quantitative metric for explosion risk assessment. To further enhance model performance, a multi-stage progressive training strategy was developed to jointly optimize the dual networks. Experimental results demonstrate that compared with mesh-based graph network (MGN), the dual-network architecture effectively decouples the tasks of concentration field prediction and equivalent gas cloud volume prediction. This approach significantly mitigates the interference of weight factors in single-objective loss functions during the training process. The multi-stage training strategy, through stepwise parameter optimization, addresses the issue of insufficient data fitting encountered in traditional methods, significantly reducing the mean absolute percentage error\begin{document}$ {{ \varepsilon }}_{\rm{MAPE}} $\end{document} ![]()
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Gas leakage and explosion accidents pose a serious threat to public safety. A critical prerequisite for accurately predicting the explosive effects of combustible gas leakage lies in determining the concentration distribution following the leakage. To develop a real-time, full-field spatiotemporal prediction model for combustible gas leakage and diffusion, and to achieve efficient prediction of the equivalent gas cloud volume, a novel graph neural network model based on a dual-neural-network architecture and a multi-stage training strategy, named multi-stage dual graph neural network (MSDGNN), was proposed. The MSDGNN model consists of two synergistic sub-networks: (1) a concentration network (Ncon), which establishes the mapping relationship between the concentration fields of two consecutive timesteps, and (2) a volume network (Nvol), which generates the equivalent gas cloud volume at each timestep to provide a quantitative metric for explosion risk assessment. To further enhance model performance, a multi-stage progressive training strategy was developed to jointly optimize the dual networks. Experimental results demonstrate that compared with mesh-based graph network (MGN), the dual-network architecture effectively decouples the tasks of concentration field prediction and equivalent gas cloud volume prediction. This approach significantly mitigates the interference of weight factors in single-objective loss functions during the training process. The multi-stage training strategy, through stepwise parameter optimization, addresses the issue of insufficient data fitting encountered in traditional methods, significantly reducing the mean absolute percentage error
, Available online , doi: 10.11883/bzycj-2024-0388
Abstract:
In a reinforced concrete (RC) box structure, the dissipation of blast waves is restricted, and damage to the structure can be intensified due to multiple reflections. To thoroughly investigate the load characteristics and dynamic behavior of internal explosions in an RC box structure, the applicability of the finite element method was verified by replicating internal explosion tests on fully enclosed and semi-enclosed (with venting openings) RC box structures. Based on this, numerical simulations of internal explosions were conducted for the prototypical RC box structure and the type of terrorist bombing attacks specified by the Federal Emergency Management Agency (FEMA) under three explosion scenarios and four venting areas. The influence of venting area on the load characteristics at the inner surfaces and corners, the load distribution on the inner surfaces, and the time histories of displacement and velocity at the centers of the inner surfaces under internal explosion loads were explored. Additionally, a formula for calculating the total impulse of the structure’s inner surface was proposed, considering both the venting area and the spatial distribution of the impulse. The results show that the venting area has a negligible effect on the overpressure, while the impulse decreases exponentially with increasing venting area. The load distribution characteristics on the structure’s inner surface are significantly influenced by the structural dimensions, exhibiting an “indented” or “W” pattern. The maximum displacement at the centers of walls and slabs is reduced by about 50% as the venting coefficient changes from 0.457 to 1.220. Finally, based on the total impulse and maximum displacement response of each component under free-field explosion loads, a calculation method for the impulse and damage enhancement coefficient was proposed based on the venting area, effectively predicting the internal explosion load and the structure’s dynamic behavior at various venting coefficients.
In a reinforced concrete (RC) box structure, the dissipation of blast waves is restricted, and damage to the structure can be intensified due to multiple reflections. To thoroughly investigate the load characteristics and dynamic behavior of internal explosions in an RC box structure, the applicability of the finite element method was verified by replicating internal explosion tests on fully enclosed and semi-enclosed (with venting openings) RC box structures. Based on this, numerical simulations of internal explosions were conducted for the prototypical RC box structure and the type of terrorist bombing attacks specified by the Federal Emergency Management Agency (FEMA) under three explosion scenarios and four venting areas. The influence of venting area on the load characteristics at the inner surfaces and corners, the load distribution on the inner surfaces, and the time histories of displacement and velocity at the centers of the inner surfaces under internal explosion loads were explored. Additionally, a formula for calculating the total impulse of the structure’s inner surface was proposed, considering both the venting area and the spatial distribution of the impulse. The results show that the venting area has a negligible effect on the overpressure, while the impulse decreases exponentially with increasing venting area. The load distribution characteristics on the structure’s inner surface are significantly influenced by the structural dimensions, exhibiting an “indented” or “W” pattern. The maximum displacement at the centers of walls and slabs is reduced by about 50% as the venting coefficient changes from 0.457 to 1.220. Finally, based on the total impulse and maximum displacement response of each component under free-field explosion loads, a calculation method for the impulse and damage enhancement coefficient was proposed based on the venting area, effectively predicting the internal explosion load and the structure’s dynamic behavior at various venting coefficients.
, Available online , doi: 10.11883/bzycj-2025-0134
Abstract:
To explore the anti-penetration abilities of irregular structures made of high-strength alloy steel, a target enhanced with ultra-high-strength spherical structures (UHS-SS) was manufactured in this work. The UHS-SS is fabricated from ultra-high-strength steel (UHSS) and mechanically anchored to the target via threaded high-tensile rods, ensuring structural integrity under projectile penetration loading. A series of penetration tests at an impact velocity of 400 m/s was performed using a 125 mm diameter cannon. The yaw-induced projectile deflection was recorded at5000 s−1, and the failure mode and penetration depth of the projectile were obtained. Through a comparative analysis of anti-penetration experimental results between semi-infinite concrete targets and UHS-SS-reinforced targets, the influences of ultra-high mechanical performances and the spherical yaw-inducing structure on the deflection and fragmentation of the projectile were disclosed. The test results reveal that at a penetration velocity of 400 m/s, the dimensionless penetration depth of the UHS-SS target is 0.11, and the penetration resistance of the UHS-SS target is about 9 times that of C40 concrete. The anti-penetration performance of UHS-SS is significantly enhanced in comparison to that of the ordinary concrete target. Furthermore, as the projectile penetrates the UHS-SS target, the resultant force on the projectile is in a different direction from that of the projectile velocity, which can deflect and shatter the projectile. The behavior of ricocheting off the surface, deflection-induced secondary impact, and fragmentation of the projectile occurred during the anti-penetration test of the UHS-SS target, and the maximal deflection angle was 83º during the experiment, preventing the projectile from penetrating the interior of the protective structure. The UHS-SS target has a severe erosion effect on the projectile at a lower speed of 400m/s, which resulted in a mass loss rate of 23.66% in the experiment. Therefore, the risk of a ground-penetrating weapon penetrating the protective works and detonating is significantly reduced．
To explore the anti-penetration abilities of irregular structures made of high-strength alloy steel, a target enhanced with ultra-high-strength spherical structures (UHS-SS) was manufactured in this work. The UHS-SS is fabricated from ultra-high-strength steel (UHSS) and mechanically anchored to the target via threaded high-tensile rods, ensuring structural integrity under projectile penetration loading. A series of penetration tests at an impact velocity of 400 m/s was performed using a 125 mm diameter cannon. The yaw-induced projectile deflection was recorded at
, Available online , doi: 10.11883/bzycj-2024-0274
Abstract:
The pressure characteristics and structural deformation mechanism of aluminum honeycomb sandwich plates (AHSPs) under water-entry impact were investigated through experimental methods. A self-designed drop experimental platform in the water tank was established, and the water-entry impact experiments of AHSPs at different drop heights were carried out. Meanwhile, the deformation of the face sheets was measured by a 3D scanner, and the time history of water impact pressure at different measuring points was monitored. Furthermore, the repeatability of the experiment was verified. On this basis, the water impact load characteristics of AHSPs during the process of water entry were studied and compared with those of other structures in published papers. In addition, the deformation modes and permanent deflection characteristics of AHSPs were analyzed, and the fitting formulas of the permanent deflection of the face sheets and the compression of the core were proposed. Results show that the distribution of the water impact pressure on the front sheet of AHSPs is uneven. However, within the range of drop heights studied, the peak value of the water impact pressure is approximately linear with the drop height. Additionally, compared to the water entry of rigid plates, the peak value of the water impact pressure of AHSPs is smaller. Compared with the mass equivalent aluminum plates, the peak value of the water impact pressure of AHSPs is much smaller, while the pressure duration of AHSPs is longer. The deformation modes of the face sheets of AHSPs at different drop heights are almost the same. Besides, with the increase of the drop height, the permanent deflections of the front and back faces of AHSPs increase approximately in the form of a quadratic parabola with decreasing slope. Suffering from water entry impact loadings, the permanent deflections of the back sheet of AHSPs are smaller than those of the equivalent aluminum plates, indicating that the AHSPs have better impact resistance compared with the equivalent aluminum plates.
The pressure characteristics and structural deformation mechanism of aluminum honeycomb sandwich plates (AHSPs) under water-entry impact were investigated through experimental methods. A self-designed drop experimental platform in the water tank was established, and the water-entry impact experiments of AHSPs at different drop heights were carried out. Meanwhile, the deformation of the face sheets was measured by a 3D scanner, and the time history of water impact pressure at different measuring points was monitored. Furthermore, the repeatability of the experiment was verified. On this basis, the water impact load characteristics of AHSPs during the process of water entry were studied and compared with those of other structures in published papers. In addition, the deformation modes and permanent deflection characteristics of AHSPs were analyzed, and the fitting formulas of the permanent deflection of the face sheets and the compression of the core were proposed. Results show that the distribution of the water impact pressure on the front sheet of AHSPs is uneven. However, within the range of drop heights studied, the peak value of the water impact pressure is approximately linear with the drop height. Additionally, compared to the water entry of rigid plates, the peak value of the water impact pressure of AHSPs is smaller. Compared with the mass equivalent aluminum plates, the peak value of the water impact pressure of AHSPs is much smaller, while the pressure duration of AHSPs is longer. The deformation modes of the face sheets of AHSPs at different drop heights are almost the same. Besides, with the increase of the drop height, the permanent deflections of the front and back faces of AHSPs increase approximately in the form of a quadratic parabola with decreasing slope. Suffering from water entry impact loadings, the permanent deflections of the back sheet of AHSPs are smaller than those of the equivalent aluminum plates, indicating that the AHSPs have better impact resistance compared with the equivalent aluminum plates.
, Available online , doi: 10.11883/bzycj-2025-0037
Abstract:
Shock initiation and ignition techniques driven by electrically exploded metallic bridge foils with insulating flyers have been widely implemented in initiation and ignition system of weapon. To address the deficiency in existing research regarding the description of the flow field evolution during the motion of flyer and promote the development of this technology towards efficient energy utilization and miniaturization, a double-pulse laser schlieren transient observation system was constructed. This system enables the acquisition of density distributions of the flow field and the motion distance of the flyer at different time. Additionally, a two-dimensional axisymmetric fluid dynamics calculation model and calculation method for the motion process of flyer driven by the electric explosion of metal foil were established, and corresponding numerical simulation calculations were performed in consideration of the evolution laws of the flow field inside and outside the acceleration chamber under the effects of the motion of flyer, the compression of shock wave, and the expansion of high-temperature and high-pressure plasma. The phase transition of bridge foil from solid phase to plasma phase was described by phase transition fraction, the state of plasma with high temperature and pressure was described by the state equation of plasma which consider the changes in particle number and coulomb interaction between particles, and the motion of flyer was described by dynamic grid model. The calculated flow field density distribution closely matches the experimental results, and the maximum errors in flyer motion distance and velocity are 6.1% and 8.1%, respectively, validating the accuracy of the calculation model and calculation method. The research results indicate that when the capacitance is 0.33 μF and the initiation voltage is2800 V, within the research range, the maximum pressure in the flow field remains approximately at 1×107 Pa; the temperature in the flow field gradually decreases from 9950 K at 516 ns to 3100 K at 2310 ns; and the plasma phase distribution in the flow field gradually evolves from a flat shape to a long strip shape, with the maximum diffusion distance of plasma in the direction perpendicular to the motion of the flyer being 0.8 mm. At 1360 ns, upon flyer breakthrough the shock wave front, a distinct bulge-shaped profile emerges in the leading edge of both pressure and temperature distributions within the flow field.
Shock initiation and ignition techniques driven by electrically exploded metallic bridge foils with insulating flyers have been widely implemented in initiation and ignition system of weapon. To address the deficiency in existing research regarding the description of the flow field evolution during the motion of flyer and promote the development of this technology towards efficient energy utilization and miniaturization, a double-pulse laser schlieren transient observation system was constructed. This system enables the acquisition of density distributions of the flow field and the motion distance of the flyer at different time. Additionally, a two-dimensional axisymmetric fluid dynamics calculation model and calculation method for the motion process of flyer driven by the electric explosion of metal foil were established, and corresponding numerical simulation calculations were performed in consideration of the evolution laws of the flow field inside and outside the acceleration chamber under the effects of the motion of flyer, the compression of shock wave, and the expansion of high-temperature and high-pressure plasma. The phase transition of bridge foil from solid phase to plasma phase was described by phase transition fraction, the state of plasma with high temperature and pressure was described by the state equation of plasma which consider the changes in particle number and coulomb interaction between particles, and the motion of flyer was described by dynamic grid model. The calculated flow field density distribution closely matches the experimental results, and the maximum errors in flyer motion distance and velocity are 6.1% and 8.1%, respectively, validating the accuracy of the calculation model and calculation method. The research results indicate that when the capacitance is 0.33 μF and the initiation voltage is
, Available online , doi: 10.11883/bzycj-2024-0483
Abstract:
To enhance the damage efficiency of fluoropolymer-based reactive fragments and broaden their application range, a novel core-shell composite structure active fragment has been proposed. To improve the strength of the matrix material, carbon fiber was introduced via a wet mixing method. Under specific sintering conditions, two types of samples were prepared: PTFE/Al/CF tungsten powder and PTFE/Al/CF tungsten ball. The basic mechanical properties of these samples were tested. The addition of tungsten powder was found to increase the dynamic compressive strength of the composite. Penetration tests were conducted on 3 mm+3 mm+2 mm+2 mm multi-layer interval aluminum targets using both types of fragments. The experimental data were automatically processed using a Python-based program, yielding the perforation area, deformation volume, and reaction light intensity for each layer of the target plate. The damage characteristics of the multi-interval target under different velocity and constraint conditions were compared and analyzed. The results show that the core-shell type fragment exhibits superior penetration ability. It can penetrate all four layers of the target plates at low speeds, although the perforation area is relatively small, with a perforation diameter approximately 0.95 times the fragment diameter. In contrast, the homogeneous fragment has a larger perforation area but weaker penetration ability. Its perforation diameter is about 1.21 times the fragment diameter, and it can only penetrate three layers of target plates at high speeds. The steel shell constraint significantly enhances the punching and penetration capabilities of the fragments. The primary active reaction of the fragment occurs during impact with the second layer of the target. The energy release reaction has a limited effect on improving the punching effect. The differences in damage characteristics are mainly attributed to the mechanical properties of the fragments. These findings provide valuable insights for the structural design and damage effect evaluation of reactive fragments.
To enhance the damage efficiency of fluoropolymer-based reactive fragments and broaden their application range, a novel core-shell composite structure active fragment has been proposed. To improve the strength of the matrix material, carbon fiber was introduced via a wet mixing method. Under specific sintering conditions, two types of samples were prepared: PTFE/Al/CF tungsten powder and PTFE/Al/CF tungsten ball. The basic mechanical properties of these samples were tested. The addition of tungsten powder was found to increase the dynamic compressive strength of the composite. Penetration tests were conducted on 3 mm+3 mm+2 mm+2 mm multi-layer interval aluminum targets using both types of fragments. The experimental data were automatically processed using a Python-based program, yielding the perforation area, deformation volume, and reaction light intensity for each layer of the target plate. The damage characteristics of the multi-interval target under different velocity and constraint conditions were compared and analyzed. The results show that the core-shell type fragment exhibits superior penetration ability. It can penetrate all four layers of the target plates at low speeds, although the perforation area is relatively small, with a perforation diameter approximately 0.95 times the fragment diameter. In contrast, the homogeneous fragment has a larger perforation area but weaker penetration ability. Its perforation diameter is about 1.21 times the fragment diameter, and it can only penetrate three layers of target plates at high speeds. The steel shell constraint significantly enhances the punching and penetration capabilities of the fragments. The primary active reaction of the fragment occurs during impact with the second layer of the target. The energy release reaction has a limited effect on improving the punching effect. The differences in damage characteristics are mainly attributed to the mechanical properties of the fragments. These findings provide valuable insights for the structural design and damage effect evaluation of reactive fragments.
, 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.
