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, Available online , doi: 10.11883/bzycj-2024-0284
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Study on gas deflagration-to-detonation transition (DDT) is of great significance for the research and development of industrial explosion prevention and detonation propulsion technology. Staggered array of obstacles is a typical obstacle layout that may be involved in the gas ignition and explosion scenario. Its existence usually significantly promotes the occurrence of DDT. In view of the lack of understanding of DDT in staggered array of obstacles, high-precision algorithm and dynamic adaptive grid were applied to solve the two-dimensional, fully compressible reactivity Navier-Stokes equations coupled with a calibrated chemical-diffusive model. Numerical investigation on the initiation process of DDT of premixed hydrogen and air in staggered array of square obstacles under different obstacle spacings was carried out. The results showed that decreasing obstacle spacing is beneficial to increase flame surface area in the early stage of flame acceleration and enhance compression of unburned gas by shock wave in the later stage, thus shortening DDT run-up time and distance. However, when the obstacle spacing is reduced to a threshold value, stuttering detonation occurs and the DDT run-up distance increases. The occurrence of DDT is mainly caused by the interaction between the flame and the shock wave reflected from the front wall of obstacle. The detonation partially decouples when it diffracts around an obstacle. Detonation re-initiation may be triggered when the decoupled detonation collides with a wall or with the shock wave or failure detonation wave from the other side of the obstacle. If the obstacle spacing is too small, the shock wave intensity decays significantly during detonation decoupling. This can easily lead to detonation failure. In addition, shock waves can be reflected off the staggered array of square obstacles in the vertical and parallel directions to the flame propagation direction, which help shock waves to act on the flame and unburned gas mixture. Therefore, DDT is more likely to be initiated in the staggered array of square obstacles than that of circular obstacles.
Study on gas deflagration-to-detonation transition (DDT) is of great significance for the research and development of industrial explosion prevention and detonation propulsion technology. Staggered array of obstacles is a typical obstacle layout that may be involved in the gas ignition and explosion scenario. Its existence usually significantly promotes the occurrence of DDT. In view of the lack of understanding of DDT in staggered array of obstacles, high-precision algorithm and dynamic adaptive grid were applied to solve the two-dimensional, fully compressible reactivity Navier-Stokes equations coupled with a calibrated chemical-diffusive model. Numerical investigation on the initiation process of DDT of premixed hydrogen and air in staggered array of square obstacles under different obstacle spacings was carried out. The results showed that decreasing obstacle spacing is beneficial to increase flame surface area in the early stage of flame acceleration and enhance compression of unburned gas by shock wave in the later stage, thus shortening DDT run-up time and distance. However, when the obstacle spacing is reduced to a threshold value, stuttering detonation occurs and the DDT run-up distance increases. The occurrence of DDT is mainly caused by the interaction between the flame and the shock wave reflected from the front wall of obstacle. The detonation partially decouples when it diffracts around an obstacle. Detonation re-initiation may be triggered when the decoupled detonation collides with a wall or with the shock wave or failure detonation wave from the other side of the obstacle. If the obstacle spacing is too small, the shock wave intensity decays significantly during detonation decoupling. This can easily lead to detonation failure. In addition, shock waves can be reflected off the staggered array of square obstacles in the vertical and parallel directions to the flame propagation direction, which help shock waves to act on the flame and unburned gas mixture. Therefore, DDT is more likely to be initiated in the staggered array of square obstacles than that of circular obstacles.
, Available online , doi: 10.11883/bzycj-2024-0452
Abstract:
The leakage of combustible gas could lead to serious explosion accidents, which could cause great damage to people’s lives and property. Explosion suppression technology can effectively reduce the consequences of the explosion accidents, which is an important part of combustible gas explosion safety protection technology. As the core component of explosion suppression device, the performance of the explosion suppressant can directly affect the reliability of explosion suppression system. The research results in the field of explosion suppression at home and abroad are focused on, and the explosion suppression powder and its inhibition mechanism are systematically summarized and analyzed. Based on the different compositions, the explosion suppressing powder is divided into one-component and compound materials. According to the difference of the suppressing mechanism, the one-component suppressing powder is divided into active powder and inert powder. Due to the synergetic effects of different substances, the development of the compound material is the research hotspot. In the literature review part, this paper follows the structure “General introduction of powder materials—Related experimental and theoretical research—Suppression mechanism summary”. The first part provides the general introduction of the material, including the origin, structure and property. The second part offers the summary of the related research result about the material. The third part focuses on the physical and chemical suppression mechanism of different material, which contributes to the deeper understanding of the suppression effect. Finally, the existing problems of the research at present is summarized and the development of the future research work is discussed. In addition, this article proposes to standardize the testing process, emphasizes the use of numerical simulation to guide the suppressing of material synthesis and reduce the blindness of research. The aim of this review is to provide scientific understanding and technical support for the development of high-efficiency explosion suppression technology.
The leakage of combustible gas could lead to serious explosion accidents, which could cause great damage to people’s lives and property. Explosion suppression technology can effectively reduce the consequences of the explosion accidents, which is an important part of combustible gas explosion safety protection technology. As the core component of explosion suppression device, the performance of the explosion suppressant can directly affect the reliability of explosion suppression system. The research results in the field of explosion suppression at home and abroad are focused on, and the explosion suppression powder and its inhibition mechanism are systematically summarized and analyzed. Based on the different compositions, the explosion suppressing powder is divided into one-component and compound materials. According to the difference of the suppressing mechanism, the one-component suppressing powder is divided into active powder and inert powder. Due to the synergetic effects of different substances, the development of the compound material is the research hotspot. In the literature review part, this paper follows the structure “General introduction of powder materials—Related experimental and theoretical research—Suppression mechanism summary”. The first part provides the general introduction of the material, including the origin, structure and property. The second part offers the summary of the related research result about the material. The third part focuses on the physical and chemical suppression mechanism of different material, which contributes to the deeper understanding of the suppression effect. Finally, the existing problems of the research at present is summarized and the development of the future research work is discussed. In addition, this article proposes to standardize the testing process, emphasizes the use of numerical simulation to guide the suppressing of material synthesis and reduce the blindness of research. The aim of this review is to provide scientific understanding and technical support for the development of high-efficiency explosion suppression technology.
, Available online , 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.
, 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-2025-0128
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Understanding the generation, transformation, and dissipation mechanisms of energy in high-pressure tanks during fire scenarios is of critical significance for the consequence assessment of explosion accidents. This study investigates the differences in properties between high-pressure hydrogen storage tanks and nitrogen tanks under fire conditions through comparative experiments. Fire tests were conducted using 6.8L-30MPa Type Ⅲ tanks. The results indicate that fire exposure can significantly impair the pressure-bearing capacity of the tanks. Specifically, the critical bursting pressure decreased from 125.1 MPa at room temperature to 46.8 MPa under fire conditions, representing a reduction of 62.6%. The explosion dynamics of hydrogen tanks were characterized by typical physical-chemical composite features. A fireball with a diameter of 9m was formed during the explosion. The peak shockwave pressure measured at a distance of 2 m reached 882.47 kPa, with a positive pressure duration of 168.11 ms. In contrast, nitrogen tanks experienced only physical explosions, with a peak shockwave pressure of 59.42 kPa and a positive pressure duration of merely 2.17 ms. This study analyzed the energy conversion pathways during explosions of high-compressed gas tanks (H2 and N2) in open environments. A novel method for assessing the blast power of hydrogen storage cylinder explosions in unconfined spaces was developed. Initially, the physical explosion energy was calculated based on fundamental parameters such as critical burst pressure, nominal volume, and initial filling pressure of the high-pressure tanks. The applicability of five mechanical energy calculation models was compared. Subsequently, the mass of hydrogen was determined using the actual gas equation, and the total chemical explosion energy was derived by integrating the heat of combustion of hydrogen. Finally, considering the contributions of mechanical and chemical energy to the shock wave intensity, the total explosion energy was converted into shock wave energy using an open space energy correction factor. Quantitative analysis and error verification were conducted in conjunction with measured data. The findings of this research provide essential support for enhancing risk assessment of explosion accidents involving high-pressure hydrogen storage devices.
Understanding the generation, transformation, and dissipation mechanisms of energy in high-pressure tanks during fire scenarios is of critical significance for the consequence assessment of explosion accidents. This study investigates the differences in properties between high-pressure hydrogen storage tanks and nitrogen tanks under fire conditions through comparative experiments. Fire tests were conducted using 6.8L-30MPa Type Ⅲ tanks. The results indicate that fire exposure can significantly impair the pressure-bearing capacity of the tanks. Specifically, the critical bursting pressure decreased from 125.1 MPa at room temperature to 46.8 MPa under fire conditions, representing a reduction of 62.6%. The explosion dynamics of hydrogen tanks were characterized by typical physical-chemical composite features. A fireball with a diameter of 9m was formed during the explosion. The peak shockwave pressure measured at a distance of 2 m reached 882.47 kPa, with a positive pressure duration of 168.11 ms. In contrast, nitrogen tanks experienced only physical explosions, with a peak shockwave pressure of 59.42 kPa and a positive pressure duration of merely 2.17 ms. This study analyzed the energy conversion pathways during explosions of high-compressed gas tanks (H2 and N2) in open environments. A novel method for assessing the blast power of hydrogen storage cylinder explosions in unconfined spaces was developed. Initially, the physical explosion energy was calculated based on fundamental parameters such as critical burst pressure, nominal volume, and initial filling pressure of the high-pressure tanks. The applicability of five mechanical energy calculation models was compared. Subsequently, the mass of hydrogen was determined using the actual gas equation, and the total chemical explosion energy was derived by integrating the heat of combustion of hydrogen. Finally, considering the contributions of mechanical and chemical energy to the shock wave intensity, the total explosion energy was converted into shock wave energy using an open space energy correction factor. Quantitative analysis and error verification were conducted in conjunction with measured data. The findings of this research provide essential support for enhancing risk assessment of explosion accidents involving high-pressure hydrogen storage devices.
, Available online , doi: 10.11883/bzycj-2025-0101
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Lattice mechanical metamaterials have been widely used in various fields due to the lightweight, flexible designability and excellent impact resistance. In this paper, an enhanced X-shaped lattice mechanical metamaterial was designed and fabricated by selective laser melting. The dynamic crushing behavior and energy absorption mechanism of this metamaterials subjected to low-velocity impact were explored experimentally and numerically. The influence of impact velocity on the deformation mode and energy absorption capability of the enhanced X-shaped lattice mechanical metamaterials was analyzed. It is shown that the impact velocity has significant effects on the deformation modes of the mechanical metamaterials. At the lower impact velocities, the deformation mode of lattice mechanical metamaterials resembles that observed under quasi-static compression, characterized by the layer-by-layer crushing mode of the cells around the shear band. At the higher impact velocities, the deformation mode of lattice mechanical metamaterials transitions from X-shaped shear band to V-shaped shear band, and finally evolves into an arc-shaped shear band. The further study suggests that enhanced X-shaped lattice mechanical metamaterial exhibits a certain degree of velocity sensitivity. With the increase of the impact velocity, the initial peak stress, plateau stress, and specific energy absorption all increase correspondingly.
Lattice mechanical metamaterials have been widely used in various fields due to the lightweight, flexible designability and excellent impact resistance. In this paper, an enhanced X-shaped lattice mechanical metamaterial was designed and fabricated by selective laser melting. The dynamic crushing behavior and energy absorption mechanism of this metamaterials subjected to low-velocity impact were explored experimentally and numerically. The influence of impact velocity on the deformation mode and energy absorption capability of the enhanced X-shaped lattice mechanical metamaterials was analyzed. It is shown that the impact velocity has significant effects on the deformation modes of the mechanical metamaterials. At the lower impact velocities, the deformation mode of lattice mechanical metamaterials resembles that observed under quasi-static compression, characterized by the layer-by-layer crushing mode of the cells around the shear band. At the higher impact velocities, the deformation mode of lattice mechanical metamaterials transitions from X-shaped shear band to V-shaped shear band, and finally evolves into an arc-shaped shear band. The further study suggests that enhanced X-shaped lattice mechanical metamaterial exhibits a certain degree of velocity sensitivity. With the increase of the impact velocity, the initial peak stress, plateau stress, and specific energy absorption all increase correspondingly.
, Available online , doi: 10.11883/bzycj-2024-0153
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Impact ejecting is a critical part of the impact process and plays a pivotal role in engineering applications and scientific analyses in deep space exploration. Its importance extends to space missions such as asteroid surface anchoring for mission stability, impact sampling for scientific analysis of extraterrestrial materials, kinetic impact deflection for planetary defense strategies, and the detailed analysis of ejecta deposition patterns on planetary surfaces to understand surface evolution and regolith dynamics. With small asteroids whose surfaces are commonly covered with regolith, granular targets are employed in laboratory settings to simulate the impact ejecting process. This paper presents a review of the research progress concerning the behavior of impact ejecting on granular targets. The formation process of impact ejecting and methods for describing ejecta curtains are evaluated. An analysis of the dimensional similarity laws governing impact ejecta, along with their applicability and limitations, is conducted. Additionally, the influence of factors, such as target material parameters, impact conditions, target surface morphology, and impactor shape and structure, on impact ejecting behavior is summarized. Finally, existing research challenges are objectively identified, and potential directions for further scientific research about the behavior of impact ejecta on granular targets are proposed.
Impact ejecting is a critical part of the impact process and plays a pivotal role in engineering applications and scientific analyses in deep space exploration. Its importance extends to space missions such as asteroid surface anchoring for mission stability, impact sampling for scientific analysis of extraterrestrial materials, kinetic impact deflection for planetary defense strategies, and the detailed analysis of ejecta deposition patterns on planetary surfaces to understand surface evolution and regolith dynamics. With small asteroids whose surfaces are commonly covered with regolith, granular targets are employed in laboratory settings to simulate the impact ejecting process. This paper presents a review of the research progress concerning the behavior of impact ejecting on granular targets. The formation process of impact ejecting and methods for describing ejecta curtains are evaluated. An analysis of the dimensional similarity laws governing impact ejecta, along with their applicability and limitations, is conducted. Additionally, the influence of factors, such as target material parameters, impact conditions, target surface morphology, and impactor shape and structure, on impact ejecting behavior is summarized. Finally, existing research challenges are objectively identified, and potential directions for further scientific research about the behavior of impact ejecta on granular targets are proposed.
, Available online , doi: 10.11883/bzycj-2024-0298
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.
, Available online , doi: 10.11883/bzycj-2024-0485
Abstract:
To accurately predict the dynamic tensile fracture in concrete materials subjected to impact and blast loadings, this study first establishes a modified Monaghan artificial bulk viscosity computation method within the framework of a non-ordinary state-based peridynamics (NOSB-PD) theory to eliminate numerical oscillations. Subsequently, the corrected strain-rate computation method, previously developed, is integrated into the Kong-Fang concrete material model, which was proposed earlier by the research group to calculate accurately the strain-rate effect during sudden changes. Based on the two methods above, numerical simulations of elastic wave propagation in a one-dimensional rod are conducted, and the results demonstrate that the additional inclusion of the modified Monaghan artificial bulk viscosity force vector state into the original force vector state can effectively suppress the non-physical numerical oscillations caused by the deformation gradient approximation. The superiority of the modified Monaghan artificial bulk viscosity is validated through comparative analysis with the original Monaghan artificial bulk viscosity. Furthermore, the influence of the modified Monaghan artificial bulk viscosity parameters is investigated, and recommended values for these parameters are provided. Finally, the aforementioned model is used to numerically simulate the spall test in concrete specimens, where the effects of including or excluding the modified Monaghan artificial bulk viscosity and different strain-rate computation methods on the prediction results of dynamic tensile fracture are compared and analyzed. The numerical simulation results demonstrate that accurately predicting the dynamic tensile fracture in concrete materials requires simultaneous consideration of the modified Monaghan artificial bulk viscosity and corrected strain-rate computation. The established non-ordinary state-based peridynamics model that accounts for both the modified Monaghan artificial bulk viscosity and corrected strain-rate computation demonstrates strong capabilities in predicting crack locations and quantities based on both qualitative and quantitative analysis metrics. This work provides new insights into the numerical simulation of dynamic tensile fracture in concrete materials under impact and blast loadings.
To accurately predict the dynamic tensile fracture in concrete materials subjected to impact and blast loadings, this study first establishes a modified Monaghan artificial bulk viscosity computation method within the framework of a non-ordinary state-based peridynamics (NOSB-PD) theory to eliminate numerical oscillations. Subsequently, the corrected strain-rate computation method, previously developed, is integrated into the Kong-Fang concrete material model, which was proposed earlier by the research group to calculate accurately the strain-rate effect during sudden changes. Based on the two methods above, numerical simulations of elastic wave propagation in a one-dimensional rod are conducted, and the results demonstrate that the additional inclusion of the modified Monaghan artificial bulk viscosity force vector state into the original force vector state can effectively suppress the non-physical numerical oscillations caused by the deformation gradient approximation. The superiority of the modified Monaghan artificial bulk viscosity is validated through comparative analysis with the original Monaghan artificial bulk viscosity. Furthermore, the influence of the modified Monaghan artificial bulk viscosity parameters is investigated, and recommended values for these parameters are provided. Finally, the aforementioned model is used to numerically simulate the spall test in concrete specimens, where the effects of including or excluding the modified Monaghan artificial bulk viscosity and different strain-rate computation methods on the prediction results of dynamic tensile fracture are compared and analyzed. The numerical simulation results demonstrate that accurately predicting the dynamic tensile fracture in concrete materials requires simultaneous consideration of the modified Monaghan artificial bulk viscosity and corrected strain-rate computation. The established non-ordinary state-based peridynamics model that accounts for both the modified Monaghan artificial bulk viscosity and corrected strain-rate computation demonstrates strong capabilities in predicting crack locations and quantities based on both qualitative and quantitative analysis metrics. This work provides new insights into the numerical simulation of dynamic tensile fracture in concrete materials under impact and blast loadings.
, Available online , doi: 10.11883/bzycj-2025-0047
Abstract:
With the increasing speed of trains, the impacts of mechanical shock, arc heat, and Joule heat on the high-speed railway catenary system have become increasingly significant. The coupling effect of high temperature and impact load has emerged as a key limiting factor for the safe operation of the pantograph-catenary system. This study focuses on copper-magnesium alloy materials used in the catenary system to address the challenges of dynamic impact and friction-induced heat generation in high-speed railways. To investigate the mechanical properties of the high-speed railway pantograph-catenary system under service conditions such as dynamic impact and frictional temperature rise, a DF14.205D electronic universal testing machine and a split Hopkinson pressure bar were employed. The uniaxial compression mechanical properties of the copper-magnesium alloy in the catenary were tested over a strain rate range of 0.001 s−1 to3000 s−1 and a temperature range of 293 K to 873 K. The strain-rate effect and temperature sensitivity of the stress-strain response were carefully analyzed. The study also revealed the compression deformation mechanism and the evolution law of the alloy’s microstructure under the combined influence of strain rate and temperature. Furthermore, a dynamic constitutive model was established to accurately describe the plastic flow behavior of the material. The findings indicate that during compression, the copper-magnesium alloy materials exhibit significant strain-rate strengthening and temperature softening effects. These effects result from the combined action of work hardening, strain rate, and temperature softening. When the temperature exceeds 473 K, temperature softening becomes the dominant factor in material deformation, and the elevated temperature can stimulate dynamic recovery and dynamic recrystallization processes. The modified Johnson-Cook model was found to be capable of accurately predicting the plastic flow stress-strain response. These research outcomes provide valuable guidance and references for the safety design and evaluation of the high-speed train pantograph-catenary system during its service.
With the increasing speed of trains, the impacts of mechanical shock, arc heat, and Joule heat on the high-speed railway catenary system have become increasingly significant. The coupling effect of high temperature and impact load has emerged as a key limiting factor for the safe operation of the pantograph-catenary system. This study focuses on copper-magnesium alloy materials used in the catenary system to address the challenges of dynamic impact and friction-induced heat generation in high-speed railways. To investigate the mechanical properties of the high-speed railway pantograph-catenary system under service conditions such as dynamic impact and frictional temperature rise, a DF14.205D electronic universal testing machine and a split Hopkinson pressure bar were employed. The uniaxial compression mechanical properties of the copper-magnesium alloy in the catenary were tested over a strain rate range of 0.001 s−1 to
, Available online , doi: 10.11883/bzycj-2025-0054
Abstract:
In recent years, polyurea-coated reinforced concrete (RC) slabs have been extensively studied both experimentally and numerically for structural strengthening against contact explosions. However, theoretical investigations remain limited, particularly concerning the impact of polyurea on the local damages of the RC substrates. In this paper, an analytical model based on stress wave propagation theory was proposed to investigate the reflection of compression waves at the backside of the RC substrate slab and predict the spalling depth. Utilizing this analytical model, a quantitative and detailed discussion was presented regarding the effect of the polyurea on the critical spalling and breach of the RC substrate slab. Furthermore, the applicability of the empirical breach prediction, originally developed for uncoated RC slabs, was validated through existing experiments to predict the breach of polyurea-coated RC substrate slabs. The results indicate that polyurea affects the spalling process of the RC substrate slabs. Specifically, the net stress wave adjacent to the concrete-polyurea interface is a compression wave, while it transitions to a tensile wave in the deeper concrete. Polyurea primarily impacts the first spall of the RC substrate slab; subsequent spalling processes after the first spall align with those observed in uncoated RC slabs. Upon the occurrence of critical spalling, polyurea enhances the critical spalling resistance of RC slabs, although it significantly increases the spalling depth. Conversely, when a breach occurs, polyurea reduces the number of spalls but minimally affects on the total spalling depth. Based on these findings, the empirical method for predicting breaches of uncoated RC slabs can effectively be applied to predict the breach of RC substrate slabs coated with polyurea. The test results from more than twenty contact explosion experiments are consistent with the predicted outcomes, thereby validating the effectiveness of the analytical model and providing a method for estimating the breach of polyurea-coated RC substrate slabs.
In recent years, polyurea-coated reinforced concrete (RC) slabs have been extensively studied both experimentally and numerically for structural strengthening against contact explosions. However, theoretical investigations remain limited, particularly concerning the impact of polyurea on the local damages of the RC substrates. In this paper, an analytical model based on stress wave propagation theory was proposed to investigate the reflection of compression waves at the backside of the RC substrate slab and predict the spalling depth. Utilizing this analytical model, a quantitative and detailed discussion was presented regarding the effect of the polyurea on the critical spalling and breach of the RC substrate slab. Furthermore, the applicability of the empirical breach prediction, originally developed for uncoated RC slabs, was validated through existing experiments to predict the breach of polyurea-coated RC substrate slabs. The results indicate that polyurea affects the spalling process of the RC substrate slabs. Specifically, the net stress wave adjacent to the concrete-polyurea interface is a compression wave, while it transitions to a tensile wave in the deeper concrete. Polyurea primarily impacts the first spall of the RC substrate slab; subsequent spalling processes after the first spall align with those observed in uncoated RC slabs. Upon the occurrence of critical spalling, polyurea enhances the critical spalling resistance of RC slabs, although it significantly increases the spalling depth. Conversely, when a breach occurs, polyurea reduces the number of spalls but minimally affects on the total spalling depth. Based on these findings, the empirical method for predicting breaches of uncoated RC slabs can effectively be applied to predict the breach of RC substrate slabs coated with polyurea. The test results from more than twenty contact explosion experiments are consistent with the predicted outcomes, thereby validating the effectiveness of the analytical model and providing a method for estimating the breach of polyurea-coated RC substrate slabs.
, Available online , doi: 10.11883/bzycj-2024-0359
Abstract:
Oxy-fuel combustion is one of the effective means to reduce greenhouse gases. To grasp the combustion characteristics of the clean fuel acetylene in O2/CO2 atmosphere and to investigate the effect of different CO2 volume fraction on the lower flammable limit of acetylene, the lower flammable limit of acetylene was experimentally measured in a 5 L cylindrical explosive reaction device. With the increase of CO2 volume fraction from 14% to 85%, the experimental value of the lower flammable limit of acetylene increased from 2.64% to 3.93%, which was linearly increased in a small range. Compared with hydrocarbon fuels such as ethylene, ethane, and propylene, the lower flammability limit of alkanes, olefins, alkynes decrease sequentially, indicating that alkynes have a larger combustion range and a higher hazard factor. Based on the calculation model of limiting laminar flame velocity method, a prediction model applicable to the lower flammability limit of acetylene was established. Through the verification of experimental data, the average absolute error of this prediction model using the USC Ⅱ combustion reaction mechanism is at 0.52%, and the model is accurate and reliable. To explain the reason for the existence of the lower flammability limit from the perspective of the competition between the temperature rise of the heat generation from fuel consumption and the temperature drop of the heat dissipation from the expansion of the fuel body, this study examines the thermodynamic, chemical, and transport effects of CO2 on the lower flammability limit. The combustion reaction mechanism of USC Ⅱ is modified to incorporate the virtual substances FCO2, TCO2, and MCO2, and comparing the flammability limits of the three virtual substances as well as those of the five atmospheres of N2 and CO2. The thermodynamic, chemical and transport effects of CO2 on the lower flammability limit were discussed. The results show that the average proportion of thermodynamic effect is 64%, chemical effect is 35% and transportation effect is 1%.
Oxy-fuel combustion is one of the effective means to reduce greenhouse gases. To grasp the combustion characteristics of the clean fuel acetylene in O2/CO2 atmosphere and to investigate the effect of different CO2 volume fraction on the lower flammable limit of acetylene, the lower flammable limit of acetylene was experimentally measured in a 5 L cylindrical explosive reaction device. With the increase of CO2 volume fraction from 14% to 85%, the experimental value of the lower flammable limit of acetylene increased from 2.64% to 3.93%, which was linearly increased in a small range. Compared with hydrocarbon fuels such as ethylene, ethane, and propylene, the lower flammability limit of alkanes, olefins, alkynes decrease sequentially, indicating that alkynes have a larger combustion range and a higher hazard factor. Based on the calculation model of limiting laminar flame velocity method, a prediction model applicable to the lower flammability limit of acetylene was established. Through the verification of experimental data, the average absolute error of this prediction model using the USC Ⅱ combustion reaction mechanism is at 0.52%, and the model is accurate and reliable. To explain the reason for the existence of the lower flammability limit from the perspective of the competition between the temperature rise of the heat generation from fuel consumption and the temperature drop of the heat dissipation from the expansion of the fuel body, this study examines the thermodynamic, chemical, and transport effects of CO2 on the lower flammability limit. The combustion reaction mechanism of USC Ⅱ is modified to incorporate the virtual substances FCO2, TCO2, and MCO2, and comparing the flammability limits of the three virtual substances as well as those of the five atmospheres of N2 and CO2. The thermodynamic, chemical and transport effects of CO2 on the lower flammability limit were discussed. The results show that the average proportion of thermodynamic effect is 64%, chemical effect is 35% and transportation effect is 1%.
, Available online , doi: 10.11883/bzycj-2024-0366
Abstract:
In order to effectively predict and control the consequences of fuel-air mixture explosions in enclosed spaces and thereby reduce the casualties and property losses caused by accidents, the relationship between the explosive overpressure characteristics of fuel-air mixtures and the spatial scale of explosions was investigated. Closed square pipes with varying length-diameter ratios, volumes, and lengths were used to examine the impact of fuel-air mixture explosion overpressure characteristics by keeping the initial oil and gas concentration, ignition position, and ignition energy constant. The experimental results show that the rate of overpressure rise goes through three stages: a rapid increase period, a continuous oscillation period, and an attenuation termination period, which reveals the dynamic relationship between reaction rate and heat loss. The reduce of the nozzle area and the increase of the internal surface area of the pipeline can both lead to the decrease of the the maximum overpressure, the average overpressure rise rate, the maximum overpressure rise rate, and the explosion power. The further analysis of the experimental results reveals that the change in the nozzle area will directly affect the flame front area and reaction rate, with a more direct and significant impact on the maximum overpressure. The changes in the inner surface area have a relatively indirect effect on the maximum overpressure by regulating energy transfer and heat loss. Additionally, pipeline length is a crucial factor affecting the time to reach maximum overpressure. The increase of the pipeline not only increases the heat loss but also delays the superposition time point of the reflected wave and the incident wave, with the energy of the reflected wave undergoing relative attenuation.
In order to effectively predict and control the consequences of fuel-air mixture explosions in enclosed spaces and thereby reduce the casualties and property losses caused by accidents, the relationship between the explosive overpressure characteristics of fuel-air mixtures and the spatial scale of explosions was investigated. Closed square pipes with varying length-diameter ratios, volumes, and lengths were used to examine the impact of fuel-air mixture explosion overpressure characteristics by keeping the initial oil and gas concentration, ignition position, and ignition energy constant. The experimental results show that the rate of overpressure rise goes through three stages: a rapid increase period, a continuous oscillation period, and an attenuation termination period, which reveals the dynamic relationship between reaction rate and heat loss. The reduce of the nozzle area and the increase of the internal surface area of the pipeline can both lead to the decrease of the the maximum overpressure, the average overpressure rise rate, the maximum overpressure rise rate, and the explosion power. The further analysis of the experimental results reveals that the change in the nozzle area will directly affect the flame front area and reaction rate, with a more direct and significant impact on the maximum overpressure. The changes in the inner surface area have a relatively indirect effect on the maximum overpressure by regulating energy transfer and heat loss. Additionally, pipeline length is a crucial factor affecting the time to reach maximum overpressure. The increase of the pipeline not only increases the heat loss but also delays the superposition time point of the reflected wave and the incident wave, with the energy of the reflected wave undergoing relative attenuation.
, Available online , doi: 10.11883/bzycj-2025-0024
Abstract:
To investigate the penetration resistance of metal honeycomb tube-constrained concrete structures under hypervelocity impact, penetration experiments were conducted using a two-stage light gas gun with projectile velocities near 1 500 m/s. The material point method (MPM) was employed to simulate the penetration process and validate the reasonableness of target and projectile parameters. This method was further used to analyze the effects of honeycomb tube parameters, including wall thickness, height, diameter, and material, on the penetration resistance of the target structure. Numerical simulations showed that MPM can accurately simulate high-velocity penetration processes, with simulation results deviating from experimental data by less than 10%. Through orthogonal analysis, the factors influencing penetration depth were ranked in descending order as follows: characteristic tube depth, characteristic inner diameter, characteristic wall thickness, and material. For the cratering effect, the primary influencing factors were identified as characteristic wall thickness, characteristic tube depth, material, and characteristic inner diameter. For the projectiles tested in this study, optimization results indicated the following: A combination of 4 mm wall thickness, 150 mm height, 30 mm incircle diameter, and tungsten alloy demonstrated the best penetration resistance, reducing penetration depth by 25.1% compared to plain concrete. A combination of 4 mm wall thickness, 150 mm height, 90 mm incircle diameter, and aluminum exhibited superior resistance to the cratering effect, decreasing crater radius by 28.7% compared to plain concrete. Multi-objective optimization analysis determined the optimal overall configuration to be: 4 mm wall thickness, 150 mm height, 30 mm incircle diameter, and aluminum.
To investigate the penetration resistance of metal honeycomb tube-constrained concrete structures under hypervelocity impact, penetration experiments were conducted using a two-stage light gas gun with projectile velocities near 1 500 m/s. The material point method (MPM) was employed to simulate the penetration process and validate the reasonableness of target and projectile parameters. This method was further used to analyze the effects of honeycomb tube parameters, including wall thickness, height, diameter, and material, on the penetration resistance of the target structure. Numerical simulations showed that MPM can accurately simulate high-velocity penetration processes, with simulation results deviating from experimental data by less than 10%. Through orthogonal analysis, the factors influencing penetration depth were ranked in descending order as follows: characteristic tube depth, characteristic inner diameter, characteristic wall thickness, and material. For the cratering effect, the primary influencing factors were identified as characteristic wall thickness, characteristic tube depth, material, and characteristic inner diameter. For the projectiles tested in this study, optimization results indicated the following: A combination of 4 mm wall thickness, 150 mm height, 30 mm incircle diameter, and tungsten alloy demonstrated the best penetration resistance, reducing penetration depth by 25.1% compared to plain concrete. A combination of 4 mm wall thickness, 150 mm height, 90 mm incircle diameter, and aluminum exhibited superior resistance to the cratering effect, decreasing crater radius by 28.7% compared to plain concrete. Multi-objective optimization analysis determined the optimal overall configuration to be: 4 mm wall thickness, 150 mm height, 30 mm incircle diameter, and aluminum.
, Available online , doi: 10.11883/bzycj-2025-0058
Abstract:
To address the fracture problem of dynamic submarine cables and their protective sheaths caused by friction and collision with wind turbine platforms under harsh sea conditions, a multi-impact resistant composite protective layer was designed using EVA foam and rubber as the main materials, which possess high elasticity and excellent cushioning properties.Mechanical property tests were conducted on EVA foam materials with various relative densities under different loading conditions using a universal testing machine and drop hammer. Energy absorption efficiency, densification strain, plateau stress and maximum specific energy absorption were introduced to characterize the mechanical properties of EVA foam. The effects of relative density, strain rate and repeated loading on the energy absorption characteristics of EVA foam were revealed.Based on the matching relationship between the energy absorption per unit volume of EVA foam and the kinetic energy of dynamic submarine cables to be absorbed, the optimal thickness of the protective layer was determined, and composite protective layer specimens were fabricated. Subsequently, drop hammer impact tests were performed to compare the cushioning and energy absorption characteristics of the composite protective layer with other materials, preliminarily verifying its high energy absorption efficiency. Further drop hammer impact tests were conducted to investigate the effects of impact energy and loading cycles on the cushioning and energy absorption characteristics of the composite protective layer. The experimental results showed that: (1) Under single impact, the peak force and maximum displacement of the composite protective layer showed a linear positive correlation with the drop hammer mass and impact velocity, with energy absorption efficiency reaching 85 %; (2) Under multiple impacts, the mechanical properties of the composite protective layer exhibited remarkable stability - the maximum displacement in the fourth impact increased by only 5.5 % compared to the first impact, with fluctuations in energy absorption value and instantaneous rebound rate remaining below 5 %. The composite protective layer demonstrates unique mechanical properties that provide effective long-term protection for dynamic submarine cables under harsh marine conditions.
To address the fracture problem of dynamic submarine cables and their protective sheaths caused by friction and collision with wind turbine platforms under harsh sea conditions, a multi-impact resistant composite protective layer was designed using EVA foam and rubber as the main materials, which possess high elasticity and excellent cushioning properties.Mechanical property tests were conducted on EVA foam materials with various relative densities under different loading conditions using a universal testing machine and drop hammer. Energy absorption efficiency, densification strain, plateau stress and maximum specific energy absorption were introduced to characterize the mechanical properties of EVA foam. The effects of relative density, strain rate and repeated loading on the energy absorption characteristics of EVA foam were revealed.Based on the matching relationship between the energy absorption per unit volume of EVA foam and the kinetic energy of dynamic submarine cables to be absorbed, the optimal thickness of the protective layer was determined, and composite protective layer specimens were fabricated. Subsequently, drop hammer impact tests were performed to compare the cushioning and energy absorption characteristics of the composite protective layer with other materials, preliminarily verifying its high energy absorption efficiency. Further drop hammer impact tests were conducted to investigate the effects of impact energy and loading cycles on the cushioning and energy absorption characteristics of the composite protective layer. The experimental results showed that: (1) Under single impact, the peak force and maximum displacement of the composite protective layer showed a linear positive correlation with the drop hammer mass and impact velocity, with energy absorption efficiency reaching 85 %; (2) Under multiple impacts, the mechanical properties of the composite protective layer exhibited remarkable stability - the maximum displacement in the fourth impact increased by only 5.5 % compared to the first impact, with fluctuations in energy absorption value and instantaneous rebound rate remaining below 5 %. The composite protective layer demonstrates unique mechanical properties that provide effective long-term protection for dynamic submarine cables under harsh marine conditions.
, Available online , doi: 10.11883/bzycj-2024-0502
Abstract:
Porous materials are accompanied by pore collapse behavior during impact compression. Based on the shock wave structure observed in experiments carried out by predecessors, the theoretically analysis of the relationship between the shock wave formation process and pore collapse behavior of porous materials is made. Firstly, considering the compression curve characteristics of porous materials and the overtaking of shock wave, it is proposed that the shock wave structure of porous materials has three modes: low pressure single wave mode, double shock wave mode and high pressure single wave mode. These different shock wave modes are mainly caused by the influence of elastic-plastic mechanical behavior in pore collapse on the compression curve of porous materials. Furthermore, combined with the Wu-Jing equation of state, the calculation method of shock compression characteristics compatible with different shock wave modes is developed. The relationship between the Hugoniot Curve of porous material and dense material is established, and the calculation equation of impact specific volume compatible with single shock wave mode is obtained, which can directly calculate the critical specific volume without approximate conditions. In addition, the equation of pore collapse established by Carroll is modified by taking the linear approximation of the variation of porosity with pressure in the elastic stage and the elastic-plastic stage, and considering the relationship between the stress of the matrix material and the macroscopic stress in the porous material. Based on the calculation model of shock compression characteristics considering pore collapse behavior, the Hugoniot data of the material are calculated, and the influence of pore collapse behavior on the shock compression characteristics of porous materials is discussed. The results show that the shock compression characteristics of the material are significantly affected by the pore collapse behavior at lower pressures, and the model in this paper can predict the shock wave parameters of porous materials more accurately.
Porous materials are accompanied by pore collapse behavior during impact compression. Based on the shock wave structure observed in experiments carried out by predecessors, the theoretically analysis of the relationship between the shock wave formation process and pore collapse behavior of porous materials is made. Firstly, considering the compression curve characteristics of porous materials and the overtaking of shock wave, it is proposed that the shock wave structure of porous materials has three modes: low pressure single wave mode, double shock wave mode and high pressure single wave mode. These different shock wave modes are mainly caused by the influence of elastic-plastic mechanical behavior in pore collapse on the compression curve of porous materials. Furthermore, combined with the Wu-Jing equation of state, the calculation method of shock compression characteristics compatible with different shock wave modes is developed. The relationship between the Hugoniot Curve of porous material and dense material is established, and the calculation equation of impact specific volume compatible with single shock wave mode is obtained, which can directly calculate the critical specific volume without approximate conditions. In addition, the equation of pore collapse established by Carroll is modified by taking the linear approximation of the variation of porosity with pressure in the elastic stage and the elastic-plastic stage, and considering the relationship between the stress of the matrix material and the macroscopic stress in the porous material. Based on the calculation model of shock compression characteristics considering pore collapse behavior, the Hugoniot data of the material are calculated, and the influence of pore collapse behavior on the shock compression characteristics of porous materials is discussed. The results show that the shock compression characteristics of the material are significantly affected by the pore collapse behavior at lower pressures, and the model in this paper can predict the shock wave parameters of porous materials more accurately.
, Available online , doi: 10.11883/bzycj-2024-0514
Abstract:
Due to the rapid development of military technology, there are more deployments of new arms, high-tech weapons and large-caliber shells in regional and local warfare, contributing to a sharp surge in the incidences of craniocerebral trauma among military personnel due to blast shockwaves. Thus, blast-induced traumatic brain injury at present is considered as one of the most prominent forms of injury on the battlefield. In order to assess the craniocerebral injury of personnel under the effect of the blast shock wave, it is urgent to establish a set of scientific, rational and comprehensive evaluation methods. Using a realistic physical manikin model with Chinese human body size characteristics and a sensing system to carry out three kinds of shock wave intensity shock tube experiments, this study systematically obtained the change process of head surface overpressure, head centroid acceleration and angular velocity as well as neck force and torque of the realistic physical manikin model with time. Based on the short-term and long-term injury effects of the explosion on the human cranium and brain, based on the 3 ms criterion, head injury criterion (HIC), brain injury criteria (BrIC) and neck injury indicators to determine the damage and the degree of damage to the human body to carry out a comprehensive research and judgment. The results showed that under three different strong shockwave environments, the shock wave overpressure duration was less than 5 ms, acceleration and neck force lasted 5~6 ms, and angular velocity and neck torque lasted 50~244 ms; the peak centroid resultant acceleration in the head of the realistic physical manikin model was (54.60±3.69)g, (102.00±1.72)g and (161.50±6.36)g, and the calculated HIC15 showed that the head injury threshold was not reached; according to the combined determination of head surface pressure load and BrIC, the probability of craniocerebral injury increased significantly, and protective measures should be taken to reduce the risk of injury.
Due to the rapid development of military technology, there are more deployments of new arms, high-tech weapons and large-caliber shells in regional and local warfare, contributing to a sharp surge in the incidences of craniocerebral trauma among military personnel due to blast shockwaves. Thus, blast-induced traumatic brain injury at present is considered as one of the most prominent forms of injury on the battlefield. In order to assess the craniocerebral injury of personnel under the effect of the blast shock wave, it is urgent to establish a set of scientific, rational and comprehensive evaluation methods. Using a realistic physical manikin model with Chinese human body size characteristics and a sensing system to carry out three kinds of shock wave intensity shock tube experiments, this study systematically obtained the change process of head surface overpressure, head centroid acceleration and angular velocity as well as neck force and torque of the realistic physical manikin model with time. Based on the short-term and long-term injury effects of the explosion on the human cranium and brain, based on the 3 ms criterion, head injury criterion (HIC), brain injury criteria (BrIC) and neck injury indicators to determine the damage and the degree of damage to the human body to carry out a comprehensive research and judgment. The results showed that under three different strong shockwave environments, the shock wave overpressure duration was less than 5 ms, acceleration and neck force lasted 5~6 ms, and angular velocity and neck torque lasted 50~244 ms; the peak centroid resultant acceleration in the head of the realistic physical manikin model was (54.60±3.69)g, (102.00±1.72)g and (161.50±6.36)g, and the calculated HIC15 showed that the head injury threshold was not reached; according to the combined determination of head surface pressure load and BrIC, the probability of craniocerebral injury increased significantly, and protective measures should be taken to reduce the risk of injury.
, Available online , doi: 10.11883/bzycj-2024-0493
Abstract:
Explosion venting is one of the effective ways to prevent and control the hazards of combustible gas explosions, but the process of venting there may be a secondary explosion of the external venting gas cloud, how to achieve an effective explosion venting of combustible gas explosions to reduce the hazards posed by the explosion, has become a key direction of the current research. To this end, from the combustible gas explosion characteristics, combustible gas explosion venting characteristics and explosion venting of the external flow field of the secondary explosion and other aspects of the current domestic and foreign combustible gas explosion venting characteristics of the current research situation is summarized and analyzed, and found that the explosion risk of the pluralistic mixed system is difficult to accurately predict and evaluate, the internal and external flow field coupling explosion venting mechanism is not yet in-depth, the characterization of the explosion venting effect and the critical conditions of the secondary explosion is unknown. Based on the above problems, the outlook from the exploration of combustible gas explosion risk and disaster-causing mechanism, deepen the combustible gas explosion venting overpressure and flame evolution characteristics of the study, revealing the formation mechanism of the secondary explosion of the explosion venting external flow field. This provides an important reference for the future study of combustible gas explosion venting.
Explosion venting is one of the effective ways to prevent and control the hazards of combustible gas explosions, but the process of venting there may be a secondary explosion of the external venting gas cloud, how to achieve an effective explosion venting of combustible gas explosions to reduce the hazards posed by the explosion, has become a key direction of the current research. To this end, from the combustible gas explosion characteristics, combustible gas explosion venting characteristics and explosion venting of the external flow field of the secondary explosion and other aspects of the current domestic and foreign combustible gas explosion venting characteristics of the current research situation is summarized and analyzed, and found that the explosion risk of the pluralistic mixed system is difficult to accurately predict and evaluate, the internal and external flow field coupling explosion venting mechanism is not yet in-depth, the characterization of the explosion venting effect and the critical conditions of the secondary explosion is unknown. Based on the above problems, the outlook from the exploration of combustible gas explosion risk and disaster-causing mechanism, deepen the combustible gas explosion venting overpressure and flame evolution characteristics of the study, revealing the formation mechanism of the secondary explosion of the explosion venting external flow field. This provides an important reference for the future study of combustible gas explosion venting.
, Available online , doi: 10.11883/bzycj-2025-0106
Abstract:
To investigate the evolution of phase structure, dislocation distribution, energy absorption capacity, and impact accumulation effect of high-entropy alloys (HEA) under shock loading, molecular dynamics simulations were employed to systematically analyze the dynamic response behavior of Al0.3CoCrFeNi HEA plate subjected to single and secondary impact load. The results show that under the first impact, the phase structure evolution and energy absorption mode of the plastic region of Al0.3CoCrFeNi HEA plate exhibits significant velocity dependence. As the speed increases, the proportion of face-centered cubic structure shows a three-stage downward trend, while the disorder structure increases accordingly. Under low velocity impact (0.5-1.0 km/s), energy is mainly absorbed by dislocation network; at medium velocity impact (1.0-2.0 km/s), both dislocations and disordered atoms contribute; under high velocity impact (2.0-3.0 km/s), disordered atoms dominate energy absorption. Within the velocity range of 0.5-0.8 km/s of the rigid sphere, the dislocation line length increases linearly with the impact velocity. However, at higher impact velocities, the dislocation line length decreases due to the limitation of the plate thickness. The stress analysis shows that when the impact velocity increases, both the maximum stress and the boundary stress of the plastic zone exhibit nonlinear variations characterized by a quadratic relationship. Under the secondary impact, the Al0.3CoCrFeNi HEA plate forms a damage zone resembling a trapezoidal shape after impact. The radius of the pit within this damage zone exhibits a quadratic relationship with the impact velocity. Additionally, the minimum affected area resulting from the secondary impact also demonstrates a quadratic relationship with the impact velocity. Regarding impact resistance, as the initial impact velocity increases, the residual velocity following the secondary impact also rises, indicating a reduction in the resistance capability of HEA. At a distance of 10 nm from the impact center, the ballistic limit velocity decreases nonlinearly with increasing initial impact velocity. However, an increase in the secondary impact velocity mitigates the effects induced by the initial impact.
To investigate the evolution of phase structure, dislocation distribution, energy absorption capacity, and impact accumulation effect of high-entropy alloys (HEA) under shock loading, molecular dynamics simulations were employed to systematically analyze the dynamic response behavior of Al0.3CoCrFeNi HEA plate subjected to single and secondary impact load. The results show that under the first impact, the phase structure evolution and energy absorption mode of the plastic region of Al0.3CoCrFeNi HEA plate exhibits significant velocity dependence. As the speed increases, the proportion of face-centered cubic structure shows a three-stage downward trend, while the disorder structure increases accordingly. Under low velocity impact (0.5-1.0 km/s), energy is mainly absorbed by dislocation network; at medium velocity impact (1.0-2.0 km/s), both dislocations and disordered atoms contribute; under high velocity impact (2.0-3.0 km/s), disordered atoms dominate energy absorption. Within the velocity range of 0.5-0.8 km/s of the rigid sphere, the dislocation line length increases linearly with the impact velocity. However, at higher impact velocities, the dislocation line length decreases due to the limitation of the plate thickness. The stress analysis shows that when the impact velocity increases, both the maximum stress and the boundary stress of the plastic zone exhibit nonlinear variations characterized by a quadratic relationship. Under the secondary impact, the Al0.3CoCrFeNi HEA plate forms a damage zone resembling a trapezoidal shape after impact. The radius of the pit within this damage zone exhibits a quadratic relationship with the impact velocity. Additionally, the minimum affected area resulting from the secondary impact also demonstrates a quadratic relationship with the impact velocity. Regarding impact resistance, as the initial impact velocity increases, the residual velocity following the secondary impact also rises, indicating a reduction in the resistance capability of HEA. At a distance of 10 nm from the impact center, the ballistic limit velocity decreases nonlinearly with increasing initial impact velocity. However, an increase in the secondary impact velocity mitigates the effects induced by the initial impact.
, Available online , doi: 10.11883/bzycj-2024-0442
Abstract:
A closed space model was constructed using steel plates to examine the influence of afterburning energy load generated by explosive detonation products on the damage characteristics of confined space. Additionally, the quasi-static pressure in the confined space was simplified by applying the energy conservation law. Relying on the adiabatic index of the mixture of detonation products and air, as well as the complete afterburning degree of detonation products, a simulation method for the afterburning effect was proposed. This method was used to calculate the afterburning energy of detonation products and determine the beginning and ending times of the afterburning effect. The numerical simulation of implosion ruin in a confined space was carried out by this method. The implosion simulation considering the afterburning energy load was performed by employing two simulation methods: constant reaction rate and linearly increasing reaction rate. The results were compared with the implosion simulation results without considering the afterburning effect. The influence and degree of change of the afterburning effect on the implosion damage characteristics were analyzed. It is found that the afterburning effect with different reaction rates has a significant influence on the detonation damage characteristics, except for the temperature, in confined spaces. Moreover, the enhancement effect of the constant reaction rate is the most significant. It increased the velocity and acceleration loads under implosion in the confined space by 42.67% and 71.21%, respectively. The overpressure and quasi-static pressure were increased by 74.42% and 74.95%, respectively, and the kinetic energy was increased by approximately 212%. The proposed simulation method for the afterburning effect can better simulate the dynamic response of implosion ruin in confined spaces and provides a more accurate simulation method of the afterburning effect for the design and evaluation of explosion-proof structures.
A closed space model was constructed using steel plates to examine the influence of afterburning energy load generated by explosive detonation products on the damage characteristics of confined space. Additionally, the quasi-static pressure in the confined space was simplified by applying the energy conservation law. Relying on the adiabatic index of the mixture of detonation products and air, as well as the complete afterburning degree of detonation products, a simulation method for the afterburning effect was proposed. This method was used to calculate the afterburning energy of detonation products and determine the beginning and ending times of the afterburning effect. The numerical simulation of implosion ruin in a confined space was carried out by this method. The implosion simulation considering the afterburning energy load was performed by employing two simulation methods: constant reaction rate and linearly increasing reaction rate. The results were compared with the implosion simulation results without considering the afterburning effect. The influence and degree of change of the afterburning effect on the implosion damage characteristics were analyzed. It is found that the afterburning effect with different reaction rates has a significant influence on the detonation damage characteristics, except for the temperature, in confined spaces. Moreover, the enhancement effect of the constant reaction rate is the most significant. It increased the velocity and acceleration loads under implosion in the confined space by 42.67% and 71.21%, respectively. The overpressure and quasi-static pressure were increased by 74.42% and 74.95%, respectively, and the kinetic energy was increased by approximately 212%. The proposed simulation method for the afterburning effect can better simulate the dynamic response of implosion ruin in confined spaces and provides a more accurate simulation method of the afterburning effect for the design and evaluation of explosion-proof structures.
, Available online , doi: 10.11883/bzycj-2024-0463
Abstract:
In the construction process of drilling and blasting method for layered rock tunnel, the unbalanced distribution of explosion energy was easy to cause serious over- and under-excavation. The joint dip angle, inter-hole delay, and hole spacing were the main influencing parameters. The simulated rock mass samples with different joint dip angles were prepared by the layered pouring method, and the blasting test of layered rock mass was carried out. Based on the ABAQUS simulation software, the blasting crack propagation and stress wave propagation characteristics of layered rock mass under different joint dip angles were analyzed. The results show that the joint dip angle has a significant guiding effect on the stress wave propagation. By affecting the stress distribution, the peak strain and damage degree at different positions are different, which in turn promotes the crack propagation at the joint surface or around the blast hole. The inter-hole delay plays a key role in regulating the crack propagation path. With the increase of delay time, the stress wave superposition area of the pre-blasting hole and the post-blasting hole gradually shifts from the joint center to the surrounding of the post-blasting hole, resulting in the peak strain and damage value of the joint center increasing first and then decreasing, and the failure area of the rock mass shifts to the post-blasting hole accordingly. However, too long delay weakens the synergistic effect of the double-hole stress wave. The increase of hole spacing weakens the stress superposition in the center of the joint, so that the energy is concentrated around the borehole, and the crack propagation mode changes from joint penetration to radial distribution around the borehole. However, too large a hole spacing is easy to lead to the failure of crack penetration between holes due to insufficient energy attenuation and stress superposition, which significantly reduces the crushing efficiency of rock mass. The research results are helpful to the understanding of blasting crack propagation in layered rock mass.
In the construction process of drilling and blasting method for layered rock tunnel, the unbalanced distribution of explosion energy was easy to cause serious over- and under-excavation. The joint dip angle, inter-hole delay, and hole spacing were the main influencing parameters. The simulated rock mass samples with different joint dip angles were prepared by the layered pouring method, and the blasting test of layered rock mass was carried out. Based on the ABAQUS simulation software, the blasting crack propagation and stress wave propagation characteristics of layered rock mass under different joint dip angles were analyzed. The results show that the joint dip angle has a significant guiding effect on the stress wave propagation. By affecting the stress distribution, the peak strain and damage degree at different positions are different, which in turn promotes the crack propagation at the joint surface or around the blast hole. The inter-hole delay plays a key role in regulating the crack propagation path. With the increase of delay time, the stress wave superposition area of the pre-blasting hole and the post-blasting hole gradually shifts from the joint center to the surrounding of the post-blasting hole, resulting in the peak strain and damage value of the joint center increasing first and then decreasing, and the failure area of the rock mass shifts to the post-blasting hole accordingly. However, too long delay weakens the synergistic effect of the double-hole stress wave. The increase of hole spacing weakens the stress superposition in the center of the joint, so that the energy is concentrated around the borehole, and the crack propagation mode changes from joint penetration to radial distribution around the borehole. However, too large a hole spacing is easy to lead to the failure of crack penetration between holes due to insufficient energy attenuation and stress superposition, which significantly reduces the crushing efficiency of rock mass. The research results are helpful to the understanding of blasting crack propagation in layered rock mass.
, Available online , doi: 10.11883/bzycj-2024-0282
Abstract:
Hydrogen-doped natural gas technology has been gradually used in pipeline transportation, but hydrogen-doped natural gas is prone to leakage and explosion accidents. The study used a 20L spherical device to investigate the effects of hydrogen blending ratio and CO2 addition on the explosion pressure and flame propagation characteristics of hydrogen-doped natural gas, and the chemical reaction kinetics method was used to analyse the explosion mechanism. The results showed that the hydrogen doping ratio has a promoting effect on the hydrogen-doped natural gas explosion pressure parameters and flame propagation speed. As the hydrogen doping ratio increases, the maximum explosion pressure gradually increases, the rapid burn time and sustained burn time are gradually decreasing. The maximum explosion pressure rise rate and flame propagation speed gradually increase when the hydrogen doping ratio is less than 0.5. When the hydrogen doping ratio is greater than 0.5, the maximum explosion pressure rise rate and flame propagation speed rise rapidly. The addition of CO2 has an inhibitory effect on the explosion pressure and flame propagation speed of the mixed gas, but the suppression effect on pressure parameters with high hydrogen doping ratio is poor. Through reaction kinetic analysis, it can be seen that as the hydrogen doping ratio increases, the laminar burning velocity and adiabatic flame temperature gradually increase, the mole fraction of active free radicals and the rate of product increase significantly, and the mixing of hydrogen changes the reaction path of methane. When the hydrogen doping ratio is greater than 0.5, reactions R84, R46 and R3 enter the top ten steps of the reaction, producing H and OH radicals, which promotes the reaction. CO2 can reduce the laminar burning velocity, adiabatic flame temperature, active free radical mole fraction and rate of production of the mixed gas, but adding CO2 does not change the reaction path of methane.
Hydrogen-doped natural gas technology has been gradually used in pipeline transportation, but hydrogen-doped natural gas is prone to leakage and explosion accidents. The study used a 20L spherical device to investigate the effects of hydrogen blending ratio and CO2 addition on the explosion pressure and flame propagation characteristics of hydrogen-doped natural gas, and the chemical reaction kinetics method was used to analyse the explosion mechanism. The results showed that the hydrogen doping ratio has a promoting effect on the hydrogen-doped natural gas explosion pressure parameters and flame propagation speed. As the hydrogen doping ratio increases, the maximum explosion pressure gradually increases, the rapid burn time and sustained burn time are gradually decreasing. The maximum explosion pressure rise rate and flame propagation speed gradually increase when the hydrogen doping ratio is less than 0.5. When the hydrogen doping ratio is greater than 0.5, the maximum explosion pressure rise rate and flame propagation speed rise rapidly. The addition of CO2 has an inhibitory effect on the explosion pressure and flame propagation speed of the mixed gas, but the suppression effect on pressure parameters with high hydrogen doping ratio is poor. Through reaction kinetic analysis, it can be seen that as the hydrogen doping ratio increases, the laminar burning velocity and adiabatic flame temperature gradually increase, the mole fraction of active free radicals and the rate of product increase significantly, and the mixing of hydrogen changes the reaction path of methane. When the hydrogen doping ratio is greater than 0.5, reactions R84, R46 and R3 enter the top ten steps of the reaction, producing H and OH radicals, which promotes the reaction. CO2 can reduce the laminar burning velocity, adiabatic flame temperature, active free radical mole fraction and rate of production of the mixed gas, but adding CO2 does not change the reaction path of methane.
, Available online , doi: 10.11883/bzycj-2024-0283
Abstract:
Steel-concrete-steel composite (SCS) wall has been applied in high-rise buildings and nuclear power plants. Its performance under accidental and extreme loads during the whole life cycle deserves attention. Considering that fires and explosions often occur simultaneously, and that the mechanical properties of steel and concrete are deteriorated significantly at high temperatures, this leads to serious degradation of blast resistance of structural members. In this context, a total of 120 finite element (FE) models of SCS walls under combined fire and explosion were established using ABAQUS software. First, the FE models were verified based on existing fire resistance tests and explosion tests at room temperature on SCS walls. Then, the blast resistance mechanism of SCS walls was analyzed, and the influences of key parameters, including fire duration, explosion charge, steel plate ratio, material strength, tie bars spacing and axial compression ratio, on the explosion resistance were investigated. Finally, based on the single-degree of freedom method, the formulas were proposed to predict the maximum deformation of SCS walls under combined fire exposure and explosion. The results show that SCS walls primarily exhibit overall bending failure under coupled fire exposure and explosion. With the increase of fire duration, the contribution of the steel plate on the fire-exposed side to the energy dissipation decreases, and the plastic deformation of the steel plate on the non-fire-exposed side gradually becomes the main energy dissipation component. Fire duration, explosion charge and steel strength significantly affect the blast resistance of SCS walls under fire conditions. When exposed to fire for 90 minutes, the maximum mid-span deformation decreases by approximately 22%, as the steel yield strength increases from 235MPa to 460MPa. However, the influence of the concrete strength is minor. The maximum deformation of SCS walls can be reasonably predicted by the proposed formulas based on the single-degree of freedom method under coupled fire exposure and explosion.
Steel-concrete-steel composite (SCS) wall has been applied in high-rise buildings and nuclear power plants. Its performance under accidental and extreme loads during the whole life cycle deserves attention. Considering that fires and explosions often occur simultaneously, and that the mechanical properties of steel and concrete are deteriorated significantly at high temperatures, this leads to serious degradation of blast resistance of structural members. In this context, a total of 120 finite element (FE) models of SCS walls under combined fire and explosion were established using ABAQUS software. First, the FE models were verified based on existing fire resistance tests and explosion tests at room temperature on SCS walls. Then, the blast resistance mechanism of SCS walls was analyzed, and the influences of key parameters, including fire duration, explosion charge, steel plate ratio, material strength, tie bars spacing and axial compression ratio, on the explosion resistance were investigated. Finally, based on the single-degree of freedom method, the formulas were proposed to predict the maximum deformation of SCS walls under combined fire exposure and explosion. The results show that SCS walls primarily exhibit overall bending failure under coupled fire exposure and explosion. With the increase of fire duration, the contribution of the steel plate on the fire-exposed side to the energy dissipation decreases, and the plastic deformation of the steel plate on the non-fire-exposed side gradually becomes the main energy dissipation component. Fire duration, explosion charge and steel strength significantly affect the blast resistance of SCS walls under fire conditions. When exposed to fire for 90 minutes, the maximum mid-span deformation decreases by approximately 22%, as the steel yield strength increases from 235MPa to 460MPa. However, the influence of the concrete strength is minor. The maximum deformation of SCS walls can be reasonably predicted by the proposed formulas based on the single-degree of freedom method under coupled fire exposure and explosion.
, Available online , doi: 10.11883/bzycj-2024-0393
Abstract:
Traumatic brain injury (TBI) is the neurological disorder with the highest incidence and prevalence, and poses a huge public health burden for the whole society. An in-depth study of the biomechanics of TBI can help to improve the effectiveness of head protection, develop rapid assessment techniques and take timely interventions, thus reducing the risk of injury deterioration. As a numerical analysis tool, the finite element head model (FEHM) is able to simulate the dynamic response of the head during impact, including the spatial and temporal distribution of stress-strain in brain tissues, and the change of intracranial pressure, which provides an important basis for understanding the mechanical mechanism of traumatic brain injury (TBI). This paper summarizes in detail the current status and development of mainstream finite element models of the human head at home and abroad, traces the development of the models, summarises the characteristics of the models and introduces the research progress of TBI mechanisms based on finite element models. The summary and sorting out of related research will be helpful for the development of new FEHMs and provide theoretical guidance and technical support for the risk assessment of traumatic brain injury and the design of protective equipment.
Traumatic brain injury (TBI) is the neurological disorder with the highest incidence and prevalence, and poses a huge public health burden for the whole society. An in-depth study of the biomechanics of TBI can help to improve the effectiveness of head protection, develop rapid assessment techniques and take timely interventions, thus reducing the risk of injury deterioration. As a numerical analysis tool, the finite element head model (FEHM) is able to simulate the dynamic response of the head during impact, including the spatial and temporal distribution of stress-strain in brain tissues, and the change of intracranial pressure, which provides an important basis for understanding the mechanical mechanism of traumatic brain injury (TBI). This paper summarizes in detail the current status and development of mainstream finite element models of the human head at home and abroad, traces the development of the models, summarises the characteristics of the models and introduces the research progress of TBI mechanisms based on finite element models. The summary and sorting out of related research will be helpful for the development of new FEHMs and provide theoretical guidance and technical support for the risk assessment of traumatic brain injury and the design of protective equipment.
Preparation of NiP@Fe-SBA-15 suppressant and its inhibition mechanism on PP dust deflagration flames
, Available online , doi: 10.11883/bzycj-2024-0434
Abstract:
Polypropylene (PP) is widely utilized in industrial production, yet PP dust generated during its production and transportation can form explosive dust clouds, leading to severe dust explosion accidents that threaten personnel and equipment safety. To address this issue, a novel explosion suppressant, NiP@Fe-SBA-15, was synthesized to inhibit the propagation of PP dust combustion flames. The synthesis involved modifying SBA-15 mesoporous silica with Fe ions and subsequently loading NiP, resulting in a composite powder with uniformly dispersed active components and a well-preserved mesoporous structure. Characterization via SEM-Mapping and N2 adsorption-desorption experiments revealed that NiP@Fe-SBA-15 maintains a high specific surface area, exhibits a regulated pore structure, and shows no significant particle agglomeration. The Hartman tube explosive testing system was employed to evaluate the effect of NiP@Fe-SBA-15 on PP dust deflagration. Results indicated that as the NiP@Fe-SBA-15 additive increased, the flame propagation speed, brightness, and flame length of PP deflagration decreased significantly, with flame propagation almost completely inhibited at a suppressant dosage of 70 wt%. The dual explosion suppression mechanism of NiP@Fe-SBA-15 was analyzed. Physically, NiP@Fe-SBA-15 occupies reaction space, reducing oxygen and combustible volatile concentrations, while the SBA-15 molecular sieve, exposed by thermal decomposition of the suppressant, absorbs heat and forms a physical barrier, thereby reducing combustion intensity. Chemically, NiP decomposition releases Ni· and P· radicals that consume key free radicals (H·, O·, OH·) in combustion reactions, interrupting explosion chain reactions. Meanwhile, Fe-based species rapidly oxidize to Fe3O4, reducing oxygen availability and further weakening combustion intensity. In summary, NiP@Fe-SBA-15 was proven to be an effective explosion suppressant for PP dust explosions, reducing combustion intensity through combined physicochemical synergies. This research provides a new approach to enhancing polypropylene industry safety. Future work will focus on optimizing the industrial application of NiP@Fe-SBA-15 explosion suppressants while addressing cost, environmental sustainability, and stability issues to further advance dust explosion prevention technology.
Polypropylene (PP) is widely utilized in industrial production, yet PP dust generated during its production and transportation can form explosive dust clouds, leading to severe dust explosion accidents that threaten personnel and equipment safety. To address this issue, a novel explosion suppressant, NiP@Fe-SBA-15, was synthesized to inhibit the propagation of PP dust combustion flames. The synthesis involved modifying SBA-15 mesoporous silica with Fe ions and subsequently loading NiP, resulting in a composite powder with uniformly dispersed active components and a well-preserved mesoporous structure. Characterization via SEM-Mapping and N2 adsorption-desorption experiments revealed that NiP@Fe-SBA-15 maintains a high specific surface area, exhibits a regulated pore structure, and shows no significant particle agglomeration. The Hartman tube explosive testing system was employed to evaluate the effect of NiP@Fe-SBA-15 on PP dust deflagration. Results indicated that as the NiP@Fe-SBA-15 additive increased, the flame propagation speed, brightness, and flame length of PP deflagration decreased significantly, with flame propagation almost completely inhibited at a suppressant dosage of 70 wt%. The dual explosion suppression mechanism of NiP@Fe-SBA-15 was analyzed. Physically, NiP@Fe-SBA-15 occupies reaction space, reducing oxygen and combustible volatile concentrations, while the SBA-15 molecular sieve, exposed by thermal decomposition of the suppressant, absorbs heat and forms a physical barrier, thereby reducing combustion intensity. Chemically, NiP decomposition releases Ni· and P· radicals that consume key free radicals (H·, O·, OH·) in combustion reactions, interrupting explosion chain reactions. Meanwhile, Fe-based species rapidly oxidize to Fe3O4, reducing oxygen availability and further weakening combustion intensity. In summary, NiP@Fe-SBA-15 was proven to be an effective explosion suppressant for PP dust explosions, reducing combustion intensity through combined physicochemical synergies. This research provides a new approach to enhancing polypropylene industry safety. Future work will focus on optimizing the industrial application of NiP@Fe-SBA-15 explosion suppressants while addressing cost, environmental sustainability, and stability issues to further advance dust explosion prevention technology.
, Available online , doi: 10.11883/bzycj-2024-0431
Abstract:
Compared to concrete and steel structures, research on the blast resistance of timber structures is relatively scarce. Although experimental studies on the blast performance of light-frame wood walls have been conducted, relevant numerical studies remain limited. This study addresses the numerical modeling of light-frame wood walls under blast loads, with a focus on the determination of the dynamic increase factor (DIF) for nail connections and the failure criteria for wood studs. Based on the partial composite action theory, an analytical expression was derived to describe the relationship between the DIF for nail connections and other mechanical properties of light-frame wood walls, including the stiffness of studs, the stiffness of sheathing panels, and the stiffness of nail connections. A reasonable value for the DIF of nail connections was provided by introducing experimentally measured DIFs for wood studs and wood-frame walls. On this basis, a finite element (FE) model for blast resistance analysis of light-frame wood walls was developed. In this model, the wood studs, sheathing panels, and nail connections were represented using beam elements, shell elements, and discrete beam elements, respectively. The orthotropic characteristics of wood-based structural panels, the nonlinear dynamic behavior of nail connections, and the dynamic elastic-plastic features of wood studs were also appropriately modeled. Verification of the developed model against experimental data indicates that it can accurately predict the dynamic response of light-frame wood walls under blast loads, as well as the time and corresponding peak displacement when wood studs fracture. FE analyses also show that if the variation of the studs’ material properties is reasonably accounted for, the predictions of the dynamic response and failure mode after the fracture of studs are in good agreement with the experimental results. The developed model paves the way for assessing the blast vulnerability of light-frame wood structures in future research.
Compared to concrete and steel structures, research on the blast resistance of timber structures is relatively scarce. Although experimental studies on the blast performance of light-frame wood walls have been conducted, relevant numerical studies remain limited. This study addresses the numerical modeling of light-frame wood walls under blast loads, with a focus on the determination of the dynamic increase factor (DIF) for nail connections and the failure criteria for wood studs. Based on the partial composite action theory, an analytical expression was derived to describe the relationship between the DIF for nail connections and other mechanical properties of light-frame wood walls, including the stiffness of studs, the stiffness of sheathing panels, and the stiffness of nail connections. A reasonable value for the DIF of nail connections was provided by introducing experimentally measured DIFs for wood studs and wood-frame walls. On this basis, a finite element (FE) model for blast resistance analysis of light-frame wood walls was developed. In this model, the wood studs, sheathing panels, and nail connections were represented using beam elements, shell elements, and discrete beam elements, respectively. The orthotropic characteristics of wood-based structural panels, the nonlinear dynamic behavior of nail connections, and the dynamic elastic-plastic features of wood studs were also appropriately modeled. Verification of the developed model against experimental data indicates that it can accurately predict the dynamic response of light-frame wood walls under blast loads, as well as the time and corresponding peak displacement when wood studs fracture. FE analyses also show that if the variation of the studs’ material properties is reasonably accounted for, the predictions of the dynamic response and failure mode after the fracture of studs are in good agreement with the experimental results. The developed model paves the way for assessing the blast vulnerability of light-frame wood structures in future research.
, Available online , doi: 10.11883/bzycj-2024-0361
Abstract:
To study the damage law of calcareous conglomerate under blasting, firstly, the damage fracture process and mechanism of calcareous conglomerate under blasting load were revealed based on the theory of damage fracture mechanics. A meso-scale model of conglomerate, including filler, conglomerate and interfacial transition zone (ITZ), was established by using LS-DYNA and Fortran programming, and the propagation law of explosive stress wave and its damage characteristics were analyzed. The damage fracture process of calcareous conglomerate under blasting can be divided into four stages, namely: compression damage in both gravel and fill; tensile damage in gravel and compression damage in fill; tensile damage in both gravel and fill; and tensile damage at the intersection of gravel and fill. Numerical results show that under blasting loads, the gravel has higher equivalent stresses, the fill has the lowest, stress concentration is evident at the ITZ, and the stress gap between the gravel and the fill decreases as the distance increases. The conglomerate sustains relatively minor damage, with a notable phenomenon of damage occurring around it. However, and the filler experiences significant damage. The expansion of blasting crack in Calcareous conglomerate forms mainly along the direction of stress wave propagation. Cracks tend to develop along the filler with lower physical and mechanical properties, as well as along the junction surfaces. The damage to the gravel is comparatively less severe. Blasting blockiness is mainly manifested as the filler wrapping gravel, and the distribution of blasting blockiness is affected by the bonding force at the intersection surface and the distribution of gravel.
To study the damage law of calcareous conglomerate under blasting, firstly, the damage fracture process and mechanism of calcareous conglomerate under blasting load were revealed based on the theory of damage fracture mechanics. A meso-scale model of conglomerate, including filler, conglomerate and interfacial transition zone (ITZ), was established by using LS-DYNA and Fortran programming, and the propagation law of explosive stress wave and its damage characteristics were analyzed. The damage fracture process of calcareous conglomerate under blasting can be divided into four stages, namely: compression damage in both gravel and fill; tensile damage in gravel and compression damage in fill; tensile damage in both gravel and fill; and tensile damage at the intersection of gravel and fill. Numerical results show that under blasting loads, the gravel has higher equivalent stresses, the fill has the lowest, stress concentration is evident at the ITZ, and the stress gap between the gravel and the fill decreases as the distance increases. The conglomerate sustains relatively minor damage, with a notable phenomenon of damage occurring around it. However, and the filler experiences significant damage. The expansion of blasting crack in Calcareous conglomerate forms mainly along the direction of stress wave propagation. Cracks tend to develop along the filler with lower physical and mechanical properties, as well as along the junction surfaces. The damage to the gravel is comparatively less severe. Blasting blockiness is mainly manifested as the filler wrapping gravel, and the distribution of blasting blockiness is affected by the bonding force at the intersection surface and the distribution of gravel.
, Available online , doi: 10.11883/bzycj-2024-0279
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.
