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2025,
45(10):
101001.
doi: 10.11883/bzycj-2024-0463
Abstract:
In the construction process of drilling and blasting method for layered rock tunnel, the unbalanced distribution of explosion energy was easy to cause serious over- and under-excavation. The joint dip angle, inter-hole delay, and hole spacing were the main influencing parameters. The simulated rock mass samples with different joint dip angles were prepared by the layered pouring method, and the blasting test of layered rock mass was carried out. Based on the ABAQUS simulation software, the blasting crack propagation and stress wave propagation characteristics of layered rock mass under different joint dip angles were analyzed. The results show that the joint dip angle has a significant guiding effect on the stress wave propagation. By affecting the stress distribution, the peak strain and damage degree at different positions are different, which in turn promotes the crack propagation at the joint surface or around the blast hole. The inter-hole delay plays a key role in regulating the crack propagation path. With the increase of delay time, the stress wave superposition area of the pre-blasting hole and the post-blasting hole gradually shifts from the joint center to the surrounding of the post-blasting hole, resulting in the peak strain and damage value of the joint center increasing first and then decreasing, and the failure area of the rock mass shifts to the post-blasting hole accordingly. However, too long delay weakens the synergistic effect of the double-hole stress wave. The increase of hole spacing weakens the stress superposition in the center of the joint, so that the energy is concentrated around the borehole, and the crack propagation mode changes from joint penetration to radial distribution around the borehole. However, too large a hole spacing is easy to lead to the failure of crack penetration between holes due to insufficient energy attenuation and stress superposition, which significantly reduces the crushing efficiency of rock mass. The research results are helpful to the understanding of blasting crack propagation in layered rock mass.
In the construction process of drilling and blasting method for layered rock tunnel, the unbalanced distribution of explosion energy was easy to cause serious over- and under-excavation. The joint dip angle, inter-hole delay, and hole spacing were the main influencing parameters. The simulated rock mass samples with different joint dip angles were prepared by the layered pouring method, and the blasting test of layered rock mass was carried out. Based on the ABAQUS simulation software, the blasting crack propagation and stress wave propagation characteristics of layered rock mass under different joint dip angles were analyzed. The results show that the joint dip angle has a significant guiding effect on the stress wave propagation. By affecting the stress distribution, the peak strain and damage degree at different positions are different, which in turn promotes the crack propagation at the joint surface or around the blast hole. The inter-hole delay plays a key role in regulating the crack propagation path. With the increase of delay time, the stress wave superposition area of the pre-blasting hole and the post-blasting hole gradually shifts from the joint center to the surrounding of the post-blasting hole, resulting in the peak strain and damage value of the joint center increasing first and then decreasing, and the failure area of the rock mass shifts to the post-blasting hole accordingly. However, too long delay weakens the synergistic effect of the double-hole stress wave. The increase of hole spacing weakens the stress superposition in the center of the joint, so that the energy is concentrated around the borehole, and the crack propagation mode changes from joint penetration to radial distribution around the borehole. However, too large a hole spacing is easy to lead to the failure of crack penetration between holes due to insufficient energy attenuation and stress superposition, which significantly reduces the crushing efficiency of rock mass. The research results are helpful to the understanding of blasting crack propagation in layered rock mass.
2025,
45(10):
101101.
doi: 10.11883/bzycj-2024-0393
Abstract:
Traumatic brain injury (TBI) is the neurological disorder with the highest incidence and prevalence, and poses a huge public health burden for the whole society. An in-depth study of the biomechanics of TBI can help to improve the effectiveness of head protection, develop rapid assessment techniques and take timely interventions, thus reducing the risk of injury deterioration. As a numerical analysis tool, the finite element head model (FEHM) is able to simulate the dynamic response of the head during impact, including the spatial and temporal distribution of stress-strain in brain tissues, and the change of intracranial pressure, which provides an important basis for understanding the mechanical mechanism of TBI. This paper summarizes in detail the current status and development of mainstream finite element models of the human head at home and abroad, traces the development of the models, summarises the characteristics of the models and introduces the research progress of TBI mechanisms based on finite element models. The summary and sorting out of related research will be helpful for the development of new FEHMs and provide theoretical guidance and technical support for the risk assessment of traumatic brain injury and the design of protective equipment.
Traumatic brain injury (TBI) is the neurological disorder with the highest incidence and prevalence, and poses a huge public health burden for the whole society. An in-depth study of the biomechanics of TBI can help to improve the effectiveness of head protection, develop rapid assessment techniques and take timely interventions, thus reducing the risk of injury deterioration. As a numerical analysis tool, the finite element head model (FEHM) is able to simulate the dynamic response of the head during impact, including the spatial and temporal distribution of stress-strain in brain tissues, and the change of intracranial pressure, which provides an important basis for understanding the mechanical mechanism of TBI. This paper summarizes in detail the current status and development of mainstream finite element models of the human head at home and abroad, traces the development of the models, summarises the characteristics of the models and introduces the research progress of TBI mechanisms based on finite element models. The summary and sorting out of related research will be helpful for the development of new FEHMs and provide theoretical guidance and technical support for the risk assessment of traumatic brain injury and the design of protective equipment.
2025,
45(10):
102101.
doi: 10.11883/bzycj-2024-0366
Abstract:
In order to effectively predict and control the consequences of fuel-air mixture explosions in enclosed spaces and thereby reduce the casualties and property losses caused by accidents, the relationship between the explosive overpressure characteristics of fuel-air mixtures and the spatial scale of explosions was investigated. Closed square pipes with varying length-diameter ratios, volumes, and lengths were used to examine the impact of fuel-air mixture explosion overpressure characteristics by keeping the initial oil and gas concentration, ignition position, and ignition energy constant. The experimental results show that the rate of overpressure rise goes through three stages: a rapid increase period, a continuous oscillation period, and an attenuation termination period, which reveals the dynamic relationship between reaction rate and heat loss. The reduce of the nozzle area and the increase of the internal surface area of the pipeline can both lead to the decrease of the maximum overpressure, the average overpressure rise rate, the maximum overpressure rise rate, and the explosion power. The further analysis of the experimental results reveals that the change in the nozzle area will directly affect the flame front area and reaction rate, with a more direct and significant impact on the maximum overpressure. The changes in the inner surface area have a relatively indirect effect on the maximum overpressure by regulating energy transfer and heat loss. Additionally, pipeline length is a crucial factor affecting the time to reach the maximum overpressure. The increase of the pipeline length not only increases the heat loss but also delays the superposition time point of the reflected wave and the incident wave, with the energy of the reflected wave undergoing relative attenuation.
In order to effectively predict and control the consequences of fuel-air mixture explosions in enclosed spaces and thereby reduce the casualties and property losses caused by accidents, the relationship between the explosive overpressure characteristics of fuel-air mixtures and the spatial scale of explosions was investigated. Closed square pipes with varying length-diameter ratios, volumes, and lengths were used to examine the impact of fuel-air mixture explosion overpressure characteristics by keeping the initial oil and gas concentration, ignition position, and ignition energy constant. The experimental results show that the rate of overpressure rise goes through three stages: a rapid increase period, a continuous oscillation period, and an attenuation termination period, which reveals the dynamic relationship between reaction rate and heat loss. The reduce of the nozzle area and the increase of the internal surface area of the pipeline can both lead to the decrease of the maximum overpressure, the average overpressure rise rate, the maximum overpressure rise rate, and the explosion power. The further analysis of the experimental results reveals that the change in the nozzle area will directly affect the flame front area and reaction rate, with a more direct and significant impact on the maximum overpressure. The changes in the inner surface area have a relatively indirect effect on the maximum overpressure by regulating energy transfer and heat loss. Additionally, pipeline length is a crucial factor affecting the time to reach the maximum overpressure. The increase of the pipeline length not only increases the heat loss but also delays the superposition time point of the reflected wave and the incident wave, with the energy of the reflected wave undergoing relative attenuation.
2025,
45(10):
102102.
doi: 10.11883/bzycj-2024-0442
Abstract:
A Closed-Space Model was constructed using steel plates to examine the influence of afterburning energy load generated by explosive detonation products on the damage characteristics of confined space. Additionally, the quasi-static pressure in the confined space was simplified by applying the energy conservation law. Relying on the adiabatic index of the mixture of detonation products and air, as well as the complete afterburning degree of detonation products, a simulation method for the afterburning effect was proposed. This method was used to calculate the afterburning energy of detonation products and determine the beginning and ending times of the afterburning effect. The numerical simulation of implosion damage in a confined space was carried out by this method. The implosion simulation considering the afterburning energy load was performed by employing two simulation methods: constant reaction rate and linearly increasing reaction rate. The results were compared with the implosion simulation results without considering the afterburning effect. The influence and degree of change of the afterburning effect on the implosion damage characteristics were analyzed. It is found that the afterburning effect with different reaction rates has a significant influence on the detonation damage characteristics, except for the temperature, in confined spaces. Moreover, the enhancement effect of the constant reaction rate is the most significant. It increased the velocity and acceleration loads under implosion in the confined space by 42.67% and 71.21%, respectively. The overpressure and quasi-static pressure were increased by 74.42% and 74.95%, respectively, and the kinetic energy was increased by approximately 212%. The proposed simulation method for the afterburning effect can better simulate the dynamic response of implosion ruin in confined spaces and provides a more accurate simulation method of the afterburning effect for the design and evaluation of explosion-proof structures.
A Closed-Space Model was constructed using steel plates to examine the influence of afterburning energy load generated by explosive detonation products on the damage characteristics of confined space. Additionally, the quasi-static pressure in the confined space was simplified by applying the energy conservation law. Relying on the adiabatic index of the mixture of detonation products and air, as well as the complete afterburning degree of detonation products, a simulation method for the afterburning effect was proposed. This method was used to calculate the afterburning energy of detonation products and determine the beginning and ending times of the afterburning effect. The numerical simulation of implosion damage in a confined space was carried out by this method. The implosion simulation considering the afterburning energy load was performed by employing two simulation methods: constant reaction rate and linearly increasing reaction rate. The results were compared with the implosion simulation results without considering the afterburning effect. The influence and degree of change of the afterburning effect on the implosion damage characteristics were analyzed. It is found that the afterburning effect with different reaction rates has a significant influence on the detonation damage characteristics, except for the temperature, in confined spaces. Moreover, the enhancement effect of the constant reaction rate is the most significant. It increased the velocity and acceleration loads under implosion in the confined space by 42.67% and 71.21%, respectively. The overpressure and quasi-static pressure were increased by 74.42% and 74.95%, respectively, and the kinetic energy was increased by approximately 212%. The proposed simulation method for the afterburning effect can better simulate the dynamic response of implosion ruin in confined spaces and provides a more accurate simulation method of the afterburning effect for the design and evaluation of explosion-proof structures.
2025,
45(10):
102201.
doi: 10.11883/bzycj-2024-0431
Abstract:
Compared to concrete and steel structures, research on the blast resistance of timber structures is relatively scarce. Although experimental studies on the blast performance of light-frame wood walls have been conducted, relevant numerical studies remain limited. This study addresses the numerical modeling of light-frame wood walls under blast loads, with a focus on the determination of the dynamic increase factor (DIF) for nail connections and the failure criteria for wood studs. Based on the partial composite action theory, an analytical expression was derived to describe the relationship between the DIF for nail connections and other mechanical properties of light-frame wood walls, including the stiffness of studs, the stiffness of sheathing panels, and the stiffness of nail connections. A reasonable value for the DIF of nail connections was provided by introducing experimentally measured DIFs for wood studs and wood-frame walls. On this basis, a finite element (FE) model for blast resistance analysis of light-frame wood walls was developed. In this model, the wood studs, sheathing panels, and nail connections were represented using beam elements, shell elements, and discrete beam elements, respectively. The orthotropic characteristics of wood-based structural panels, the nonlinear dynamic behavior of nail connections, and the dynamic elastic-plastic features of wood studs were also appropriately modeled. Verification of the developed model against experimental data indicates that it can accurately predict the dynamic response of light-frame wood walls under blast loads, as well as the time and corresponding peak displacement when wood studs fracture. FE analyses also show that if the variation of the studs’ material properties is reasonably accounted for, the predictions of the dynamic response and failure mode after the fracture of studs are in good agreement with the experimental results. The developed model paves the way for assessing the blast vulnerability of light-frame wood structures in future research.
Compared to concrete and steel structures, research on the blast resistance of timber structures is relatively scarce. Although experimental studies on the blast performance of light-frame wood walls have been conducted, relevant numerical studies remain limited. This study addresses the numerical modeling of light-frame wood walls under blast loads, with a focus on the determination of the dynamic increase factor (DIF) for nail connections and the failure criteria for wood studs. Based on the partial composite action theory, an analytical expression was derived to describe the relationship between the DIF for nail connections and other mechanical properties of light-frame wood walls, including the stiffness of studs, the stiffness of sheathing panels, and the stiffness of nail connections. A reasonable value for the DIF of nail connections was provided by introducing experimentally measured DIFs for wood studs and wood-frame walls. On this basis, a finite element (FE) model for blast resistance analysis of light-frame wood walls was developed. In this model, the wood studs, sheathing panels, and nail connections were represented using beam elements, shell elements, and discrete beam elements, respectively. The orthotropic characteristics of wood-based structural panels, the nonlinear dynamic behavior of nail connections, and the dynamic elastic-plastic features of wood studs were also appropriately modeled. Verification of the developed model against experimental data indicates that it can accurately predict the dynamic response of light-frame wood walls under blast loads, as well as the time and corresponding peak displacement when wood studs fracture. FE analyses also show that if the variation of the studs’ material properties is reasonably accounted for, the predictions of the dynamic response and failure mode after the fracture of studs are in good agreement with the experimental results. The developed model paves the way for assessing the blast vulnerability of light-frame wood structures in future research.
2025,
45(10):
102202.
doi: 10.11883/bzycj-2024-0283
Abstract:
Steel-concrete-steel composite (SCS) wall has been applied in high-rise buildings and nuclear power plants. Its performance under accidental and extreme loads during the whole life cycle deserves attention. Considering that fires and explosions often occur simultaneously, and that the mechanical properties of steel and concrete are deteriorated significantly at high temperatures, this leads to serious degradation of blast resistance of structural members. In this context, a total of 120 finite element (FE) models of SCS walls under combined fire and explosion were established using ABAQUS software. First, the FE models were verified based on existing fire resistance tests and explosion tests at room temperature on SCS walls. Then, the blast resistance mechanism of SCS walls was analyzed, and the influences of key parameters, including fire duration, explosion charge, steel plate ratio, material strength, tie bars spacing and axial compression ratio, on the explosion resistance were investigated. Finally, based on the single-degree of freedom method, the formulas were proposed to predict the maximum deformation of SCS walls under combined fire exposure and explosion. The results show that SCS walls primarily exhibit overall bending failure under coupled fire exposure and explosion. With the increase of fire duration, the contribution of the steel plate on the fire-exposed side to the energy dissipation decreases, and the plastic deformation of the steel plate on the non-fire-exposed side gradually becomes the main energy dissipation component. Fire duration, explosion charge and steel strength significantly affect the blast resistance of SCS walls under fire conditions. When exposed to fire for 90 minutes, the maximum mid-span deformation decreases by approximately 22%, as the steel yield strength increases from 235 to 460 MPa. However, the influence of the concrete strength is minor. The maximum deformation of SCS walls can be reasonably predicted by the proposed formulas based on the single-degree of freedom method under coupled fire exposure and explosion.
Steel-concrete-steel composite (SCS) wall has been applied in high-rise buildings and nuclear power plants. Its performance under accidental and extreme loads during the whole life cycle deserves attention. Considering that fires and explosions often occur simultaneously, and that the mechanical properties of steel and concrete are deteriorated significantly at high temperatures, this leads to serious degradation of blast resistance of structural members. In this context, a total of 120 finite element (FE) models of SCS walls under combined fire and explosion were established using ABAQUS software. First, the FE models were verified based on existing fire resistance tests and explosion tests at room temperature on SCS walls. Then, the blast resistance mechanism of SCS walls was analyzed, and the influences of key parameters, including fire duration, explosion charge, steel plate ratio, material strength, tie bars spacing and axial compression ratio, on the explosion resistance were investigated. Finally, based on the single-degree of freedom method, the formulas were proposed to predict the maximum deformation of SCS walls under combined fire exposure and explosion. The results show that SCS walls primarily exhibit overall bending failure under coupled fire exposure and explosion. With the increase of fire duration, the contribution of the steel plate on the fire-exposed side to the energy dissipation decreases, and the plastic deformation of the steel plate on the non-fire-exposed side gradually becomes the main energy dissipation component. Fire duration, explosion charge and steel strength significantly affect the blast resistance of SCS walls under fire conditions. When exposed to fire for 90 minutes, the maximum mid-span deformation decreases by approximately 22%, as the steel yield strength increases from 235 to 460 MPa. However, the influence of the concrete strength is minor. The maximum deformation of SCS walls can be reasonably predicted by the proposed formulas based on the single-degree of freedom method under coupled fire exposure and explosion.
2025,
45(10):
102203.
doi: 10.11883/bzycj-2024-0298
Abstract:
In military operations, industrial accidents and other explosive events, head injuries caused by blast shock waves have become one of the main injury forms of injury, but the injury mechanism and damage threshold have not been clarified yet. In this paper, numerical simulation is used to study the dynamic response process of the head under explosion load, and the effects of TNT charge, air and water media on the deformation, pressure and acceleration of the cranium and brain are analyzed. First, the air-head fluid-structure interaction model is established using Euler-Lagrangian coupling method. Based on the validation of its effectiveness, the dynamic response process of the head was analyzed in terms of pressure, acceleration and frequency of the prefrontal cranium and brain tissue. By setting the initial conditions and boundary conditions, the effects of frontal and the behind shock loadings of the blast wave on the head were simulated. It has been found that the head tissue vibrates at high frequencies, up to 7 kHz, when the blast wave strikes the head directly. The acceleration on the prefrontal cranium and brain tissue had a large value initially and become small in the late stage, while the intracranial pressure varied in a cyclical manner. In the underwater environment, there were high-frequency periodic overpressure fluctuations in the brain tissues of frontal, parietal and temporal lobes, in which peak overpressure of 3.64 MPa can be generated in the prefrontal cranium, which is well above the threshold of 235 kPa for severe brain injury. In water, brain tissue is subjected to 5 times the peak pressure, a 5 fold increase in acceleration and a 2 fold increase in frequency compared to those in air. The results of this research provide a new perspective for understanding the mechanism of damage to the human brain caused by blast shock waves, and an reference for the development of future protective measures.
In military operations, industrial accidents and other explosive events, head injuries caused by blast shock waves have become one of the main injury forms of injury, but the injury mechanism and damage threshold have not been clarified yet. In this paper, numerical simulation is used to study the dynamic response process of the head under explosion load, and the effects of TNT charge, air and water media on the deformation, pressure and acceleration of the cranium and brain are analyzed. First, the air-head fluid-structure interaction model is established using Euler-Lagrangian coupling method. Based on the validation of its effectiveness, the dynamic response process of the head was analyzed in terms of pressure, acceleration and frequency of the prefrontal cranium and brain tissue. By setting the initial conditions and boundary conditions, the effects of frontal and the behind shock loadings of the blast wave on the head were simulated. It has been found that the head tissue vibrates at high frequencies, up to 7 kHz, when the blast wave strikes the head directly. The acceleration on the prefrontal cranium and brain tissue had a large value initially and become small in the late stage, while the intracranial pressure varied in a cyclical manner. In the underwater environment, there were high-frequency periodic overpressure fluctuations in the brain tissues of frontal, parietal and temporal lobes, in which peak overpressure of 3.64 MPa can be generated in the prefrontal cranium, which is well above the threshold of 235 kPa for severe brain injury. In water, brain tissue is subjected to 5 times the peak pressure, a 5 fold increase in acceleration and a 2 fold increase in frequency compared to those in air. The results of this research provide a new perspective for understanding the mechanism of damage to the human brain caused by blast shock waves, and an reference for the development of future protective measures.
2025,
45(10):
102204.
doi: 10.11883/bzycj-2024-0514
Abstract:
Due to the rapid development of military technology, there are more deployments of new arms, high-tech weapons and large-caliber shells in regional and local warfare, contributing to a sharp surge in the incidences of craniocerebral trauma among military personnel due to blast shockwaves. Thus, blast-induced traumatic brain injury at present is considered as one of the most prominent forms of injury on the battlefield. In order to assess the craniocerebral injury of personnel under the effect of the blast shock wave, it is urgent to establish a set of scientific, rational and comprehensive evaluation methods. Using a realistic physical manikin model with Chinese human body size characteristics and a sensing system to carry out three kinds of shock wave intensity shock tube experiments, this study systematically obtained the change process of head surface overpressure, head centroid acceleration and angular velocity as well as neck force and torque of the realistic physical manikin model with time. Based on the short-term and long-term injury effects of the explosion on the human cranium and brain, based on the 3 ms criterion, head injury criterion (HIC), brain injury criteria (BrIC) and neck injury indicators to determine the damage and the degree of damage to the human body to carry out a comprehensive research and judgment. The results showed that under three different strong shockwave environments, the shock wave overpressure duration was less than 5 ms, acceleration and neck force lasted 5–6 ms, and angular velocity and neck torque lasted 50–244 ms; the peak centroid resultant acceleration in the head of the realistic physical manikin model was (54.60±3.69)g, (102.00±1.72)g and (161.50±6.36)g, and the calculated HIC15 showed that the head injury threshold was not reached; according to the combined determination of head surface pressure load and BrIC, the probability of craniocerebral injury increased significantly, and protective measures should be taken to reduce the risk of injury.
Due to the rapid development of military technology, there are more deployments of new arms, high-tech weapons and large-caliber shells in regional and local warfare, contributing to a sharp surge in the incidences of craniocerebral trauma among military personnel due to blast shockwaves. Thus, blast-induced traumatic brain injury at present is considered as one of the most prominent forms of injury on the battlefield. In order to assess the craniocerebral injury of personnel under the effect of the blast shock wave, it is urgent to establish a set of scientific, rational and comprehensive evaluation methods. Using a realistic physical manikin model with Chinese human body size characteristics and a sensing system to carry out three kinds of shock wave intensity shock tube experiments, this study systematically obtained the change process of head surface overpressure, head centroid acceleration and angular velocity as well as neck force and torque of the realistic physical manikin model with time. Based on the short-term and long-term injury effects of the explosion on the human cranium and brain, based on the 3 ms criterion, head injury criterion (HIC), brain injury criteria (BrIC) and neck injury indicators to determine the damage and the degree of damage to the human body to carry out a comprehensive research and judgment. The results showed that under three different strong shockwave environments, the shock wave overpressure duration was less than 5 ms, acceleration and neck force lasted 5–6 ms, and angular velocity and neck torque lasted 50–244 ms; the peak centroid resultant acceleration in the head of the realistic physical manikin model was (54.60±3.69)g, (102.00±1.72)g and (161.50±6.36)g, and the calculated HIC15 showed that the head injury threshold was not reached; according to the combined determination of head surface pressure load and BrIC, the probability of craniocerebral injury increased significantly, and protective measures should be taken to reduce the risk of injury.
2025,
45(10):
103101.
doi: 10.11883/bzycj-2024-0361
Abstract:
To study the damage law of calcareous conglomerate under blasting, firstly, the damage fracture process and mechanism of calcareous conglomerate under blasting load were revealed based on the theory of damage fracture mechanics. A meso-scale model of conglomerate, including filler, conglomerate and interfacial transition zone (ITZ), was established by using LS-DYNA and Fortran programming, and the propagation law of explosive stress wave and its damage characteristics were analyzed. The damage fracture process of calcareous conglomerate under blasting can be divided into four stages, namely: compression damage in both gravel and fill; tensile damage in gravel and compression damage in fill; tensile damage in both gravel and fill; and tensile damage at the intersection of gravel and fill. Numerical results show that under blasting loads, the gravel has higher equivalent stresses, the fill has the lowest, stress concentration is evident at the ITZ, and the stress gap between the gravel and the fill decreases as the distance increases. The conglomerate sustains relatively minor damage, with a notable phenomenon of damage occurring around it. However, the filler experiences significant damage. The expansion of blasting crack in calcareous conglomerate forms mainly along the direction of stress wave propagation. Cracks tend to develop along the filler with lower physical and mechanical properties, as well as along the junction surfaces. The damage to the gravel is comparatively less severe. Blasting blockiness is mainly manifested as the filler wrapping gravel, and the distribution of blasting blockiness is affected by the bonding force at the intersection surface and the distribution of gravel.
To study the damage law of calcareous conglomerate under blasting, firstly, the damage fracture process and mechanism of calcareous conglomerate under blasting load were revealed based on the theory of damage fracture mechanics. A meso-scale model of conglomerate, including filler, conglomerate and interfacial transition zone (ITZ), was established by using LS-DYNA and Fortran programming, and the propagation law of explosive stress wave and its damage characteristics were analyzed. The damage fracture process of calcareous conglomerate under blasting can be divided into four stages, namely: compression damage in both gravel and fill; tensile damage in gravel and compression damage in fill; tensile damage in both gravel and fill; and tensile damage at the intersection of gravel and fill. Numerical results show that under blasting loads, the gravel has higher equivalent stresses, the fill has the lowest, stress concentration is evident at the ITZ, and the stress gap between the gravel and the fill decreases as the distance increases. The conglomerate sustains relatively minor damage, with a notable phenomenon of damage occurring around it. However, the filler experiences significant damage. The expansion of blasting crack in calcareous conglomerate forms mainly along the direction of stress wave propagation. Cracks tend to develop along the filler with lower physical and mechanical properties, as well as along the junction surfaces. The damage to the gravel is comparatively less severe. Blasting blockiness is mainly manifested as the filler wrapping gravel, and the distribution of blasting blockiness is affected by the bonding force at the intersection surface and the distribution of gravel.
2025,
45(10):
103201.
doi: 10.11883/bzycj-2024-0407
Abstract:
To explore the influence of the propellant bed accumulation distribution on the three-dimensional characteristics of initial pressure wave in the chamber during the internal ballistic process of a large-caliber modular charge gun, a three-dimensional gas-solid two-phase combustion dynamic model of the modular charge was established. Firstly, solid powder particles were treated as discrete phase. Based on Euler-Lagrange method, the motion law and accumulation distribution of propellant particles under different initial broken sizes of cartridge end caps were simulated. Then, the propellant particles were treated as continuous phase and the evolution of pressure distribution in the chamber after combustion of the powder bed with different accumulation distribution was numerically simulated using the Euler-Euler method. The results show that the characteristics of the three-dimensional flow field in the bore are affected by the difference of the initial fracture size of the cartridge end cap. When the initial breaking angle of the cartridge end cap increases from 0° to 120°, the difference of the propellant particles in the area near breech and the area near forcing cone decreases from 12.2% to 0.6% after the dispersion and settlement of the propellant particles. Additionally, the absolute value of the initial negative pressure difference between the breech and the forcing cone decreases from 1.62 MPa to 0.76 MPa. The start-up time of the bullet is extended from 2.82 ms to 2.94 ms, and the time required for the forcing cone pressure to reach its peak is increases from 4.04 ms to 4.20 ms. At the same time, complex three-dimensional pressure fluctuations were observed in the chamber. Before the bullet movement, the chamber pressure can be divided into four pressure evolution characteristics along the X-axis direction, presenting the pressure with no changing, gradually decreasing, first decreasing and then increasing, as well as gradually increasing. After the bullet movement, the chamber pressure consistently decreases along the X-axis direction. However, along the Y-axis direction, the pressure in the chamber remains essentially unchanged before and after the bullet movement. The pressure in the chamber can be also divided into four pressure evolution characteristics along the Z-axis direction, presenting basically maintaining a constant level, gradually decreasing, first decreasing and then increasing, first decreasing and then increasing and then decreasing. The research results have some reference value for the interior ballistic safety analysis of modular charge guns.
To explore the influence of the propellant bed accumulation distribution on the three-dimensional characteristics of initial pressure wave in the chamber during the internal ballistic process of a large-caliber modular charge gun, a three-dimensional gas-solid two-phase combustion dynamic model of the modular charge was established. Firstly, solid powder particles were treated as discrete phase. Based on Euler-Lagrange method, the motion law and accumulation distribution of propellant particles under different initial broken sizes of cartridge end caps were simulated. Then, the propellant particles were treated as continuous phase and the evolution of pressure distribution in the chamber after combustion of the powder bed with different accumulation distribution was numerically simulated using the Euler-Euler method. The results show that the characteristics of the three-dimensional flow field in the bore are affected by the difference of the initial fracture size of the cartridge end cap. When the initial breaking angle of the cartridge end cap increases from 0° to 120°, the difference of the propellant particles in the area near breech and the area near forcing cone decreases from 12.2% to 0.6% after the dispersion and settlement of the propellant particles. Additionally, the absolute value of the initial negative pressure difference between the breech and the forcing cone decreases from 1.62 MPa to 0.76 MPa. The start-up time of the bullet is extended from 2.82 ms to 2.94 ms, and the time required for the forcing cone pressure to reach its peak is increases from 4.04 ms to 4.20 ms. At the same time, complex three-dimensional pressure fluctuations were observed in the chamber. Before the bullet movement, the chamber pressure can be divided into four pressure evolution characteristics along the X-axis direction, presenting the pressure with no changing, gradually decreasing, first decreasing and then increasing, as well as gradually increasing. After the bullet movement, the chamber pressure consistently decreases along the X-axis direction. However, along the Y-axis direction, the pressure in the chamber remains essentially unchanged before and after the bullet movement. The pressure in the chamber can be also divided into four pressure evolution characteristics along the Z-axis direction, presenting basically maintaining a constant level, gradually decreasing, first decreasing and then increasing, first decreasing and then increasing and then decreasing. The research results have some reference value for the interior ballistic safety analysis of modular charge guns.
2025,
45(10):
103202.
doi: 10.11883/bzycj-2024-0401
Abstract:
During firing of a truck-mounted howitzer, the crew compartment structure deforms elastically due to the muzzle blast load, creating pressure disturbances in the internal flow field of cabin. The resulting overpressure causes a significant threat to personnel and equipment safety. To meet driving requirements, the crew compartment of the truck-mounted howitzer is suspended on the chassis frame via an elastic support structure. At the same time, the stiffness and damping of the support structure are important factors affecting the deformation response of the cabin structure under the impact of the muzzle blast load. Therefore, adjusting the support parameters to optimize the flow field environment inside the crew compartment demonstrates high practical utility. To investigate the effects of different cabin support conditions on the flow field overpressure inside the crew compartment of a truck-mounted howitzer, a foreign trade type of equipment was taken as the object. An entire path numerical model simulating the shock wave propagation from the cannon's muzzle to the interior of the cabin under extreme firing conditions was established. Systematic validation tests were conducted, capturing overpressure data in both the external and internal flow fields of the crew compartment, as well as the acceleration of the cabin structure. Based on the validated numerical model, simulations were performed to calculate the structural responses and internal flow field overpressures under eight different support conditions. The results indicate that while different areas within the cabin exhibit varying sensitivity to changes in support conditions, increasing the support stiffness leads to significant reductions in the peak acceleration and velocity of the cabin structure, as well as a decrease in the peak overpressure within the internal flow field. However, the presence of damping in the support structure significantly enhances the acceleration response of the cabin structure, yet it further diminishes its velocity response and lower the peak overpressure in the internal flow field of the crew compartment.
During firing of a truck-mounted howitzer, the crew compartment structure deforms elastically due to the muzzle blast load, creating pressure disturbances in the internal flow field of cabin. The resulting overpressure causes a significant threat to personnel and equipment safety. To meet driving requirements, the crew compartment of the truck-mounted howitzer is suspended on the chassis frame via an elastic support structure. At the same time, the stiffness and damping of the support structure are important factors affecting the deformation response of the cabin structure under the impact of the muzzle blast load. Therefore, adjusting the support parameters to optimize the flow field environment inside the crew compartment demonstrates high practical utility. To investigate the effects of different cabin support conditions on the flow field overpressure inside the crew compartment of a truck-mounted howitzer, a foreign trade type of equipment was taken as the object. An entire path numerical model simulating the shock wave propagation from the cannon's muzzle to the interior of the cabin under extreme firing conditions was established. Systematic validation tests were conducted, capturing overpressure data in both the external and internal flow fields of the crew compartment, as well as the acceleration of the cabin structure. Based on the validated numerical model, simulations were performed to calculate the structural responses and internal flow field overpressures under eight different support conditions. The results indicate that while different areas within the cabin exhibit varying sensitivity to changes in support conditions, increasing the support stiffness leads to significant reductions in the peak acceleration and velocity of the cabin structure, as well as a decrease in the peak overpressure within the internal flow field. However, the presence of damping in the support structure significantly enhances the acceleration response of the cabin structure, yet it further diminishes its velocity response and lower the peak overpressure in the internal flow field of the crew compartment.
2025,
45(10):
105101.
doi: 10.11883/bzycj-2024-0279
Abstract:
Prefabricated concrete bursting layer has a very important application prospect in the field of protective engineering attributed to its technical advantages including high construction efficiency and construction quality. However, compared with the monolithic cast-in-situ concrete bursting layer, the impact resistance of the prefabricated concrete bursting layer may be significantly reduced because of the interfaces between the prefabricated blocks and the cast-in-situ part. Therefore, it is important for engineers to reasonably design the prefabricated concrete bursting layer to make its penetration resistance comparable to the monolithic one. To this end, a kind of prefabricated bursting layer connected by wet joints and rebars was proposed in our previous study. In order to apply the prefabricated bursting layer in protective engineering, a series of numerical models were developed to further study its penetration resistance. Firstly, based on the Kong-Fang model and smoothed particle Galerkin (SPG) method, the numerical models were developed and validated against the experimental data of projectile penetrating monolithic and prefabricated targets. Then, the validated numerical models were further used to investigate the influences of prefabricated block size, wet joint width and anchorage length, spacing and diameter of rebars on the penetration resistance of prefabricated targets. Numerical results indicate that increasing the width of wet joints, reducing the spacing between rebars, and extending the anchorage length of rebars can significantly enhance the penetration resistance of prefabricated targets. After clarifying the influences of these parameters, an engineering design method for a prefabricated concrete bursting layer was proposed. Finally, based on this method, two prefabricated high performance concrete targets subjected to two typical types of warhead penetration were designed. Numerical results show that the penetration resistances of two prefabricated targets were comparable to monolithic targets. The proposed engineering design method can provide a reference for engineering applications of prefabricated concrete bursting layers connected by the wet joints and rebars.
Prefabricated concrete bursting layer has a very important application prospect in the field of protective engineering attributed to its technical advantages including high construction efficiency and construction quality. However, compared with the monolithic cast-in-situ concrete bursting layer, the impact resistance of the prefabricated concrete bursting layer may be significantly reduced because of the interfaces between the prefabricated blocks and the cast-in-situ part. Therefore, it is important for engineers to reasonably design the prefabricated concrete bursting layer to make its penetration resistance comparable to the monolithic one. To this end, a kind of prefabricated bursting layer connected by wet joints and rebars was proposed in our previous study. In order to apply the prefabricated bursting layer in protective engineering, a series of numerical models were developed to further study its penetration resistance. Firstly, based on the Kong-Fang model and smoothed particle Galerkin (SPG) method, the numerical models were developed and validated against the experimental data of projectile penetrating monolithic and prefabricated targets. Then, the validated numerical models were further used to investigate the influences of prefabricated block size, wet joint width and anchorage length, spacing and diameter of rebars on the penetration resistance of prefabricated targets. Numerical results indicate that increasing the width of wet joints, reducing the spacing between rebars, and extending the anchorage length of rebars can significantly enhance the penetration resistance of prefabricated targets. After clarifying the influences of these parameters, an engineering design method for a prefabricated concrete bursting layer was proposed. Finally, based on this method, two prefabricated high performance concrete targets subjected to two typical types of warhead penetration were designed. Numerical results show that the penetration resistances of two prefabricated targets were comparable to monolithic targets. The proposed engineering design method can provide a reference for engineering applications of prefabricated concrete bursting layers connected by the wet joints and rebars.
