The afterburning of TNT and structural constraints in confined spaces significantly amplify the blast load,leading to severe structural damage. This study investigates the mechanisms underlying the enhanced dynamic re...The afterburning of TNT and structural constraints in confined spaces significantly amplify the blast load,leading to severe structural damage. This study investigates the mechanisms underlying the enhanced dynamic response of reinforced concrete blast doors with four-sided restraints in confined space. Explosion tests with TNT charges ranging from 0.15 kg to 0.4 kg were conducted in a confined space,capturing overpressure loads and the dynamic response of the blast door. An internal explosion model incorporating the afterburning effect was developed using LS-DYNA software and validated against experimental data. The results reveal that the TNT afterburning effect amplifies both the initial peak overpressure and the quasi-static overpressure, resulting in increased deformation of the blast door.Within the 0.15-0.4 kg charge range, the initial overpressure peak and quasi-static overpressure increased by an average of 1.79 times and 2.21 times, respectively. Additionally, the afterburning effect enhanced the blast door's deflection by 177%. Compared to open-space scenarios, the cumulative deflection of the blast door due to repeated shock wave impacts is significantly greater in confined spaces. Furthermore, the quasi-static pressure arising from the structural constraints sustains the blast door's deflection at a high level.展开更多
In order to study the blast damage effects of aviation kerosene storage tanks,the out-field explosion experiments of 8 m3fixed-roof tanks were carried out.The fragments,shock wave and fireball thermal radiation of the...In order to study the blast damage effects of aviation kerosene storage tanks,the out-field explosion experiments of 8 m3fixed-roof tanks were carried out.The fragments,shock wave and fireball thermal radiation of the tank in the presence of bottom oil,half oil and full oil,as well as empty tank,were investigated under internal explosion by various TNT charge contents(1.8 kg,3.5 kg and 6.2 kg).The results showed that the tank roof was the only fragment produced,and the damage forms could be divided into three types.The increase of TNT charge content and oil volume enlarged the deformation of the tank,while the hole ratio presented a trend of increase first and then decrease.The H_r,maxand V_(max)values positively increased as increasing the TNT charge content and oil volume(from empty to half oil),but decreased in full oil.The Pmaxvalues had a progressive increase with the increment of TNT charge content,but not the case with the increase in oil volumes.The development of fireball was divided into three stages:tank roof‘towed'flame,jet flow flame tumbling and rising,and jet flow flame extinguishing.The Dmaxand Hf,maxvalues both increased as increasing TNT charge content and oil volumes.The oscillation phenomenon of fireball temperature was observed in the cooling process.The average temperature of fireball surface was positively correlated with TNT charge content,and negatively correlated with oil volumes.展开更多
This paper investigates the three-dimensional crack propagation and damage evolution process of metallic column shells under internal explosive loading.The calibration of four typical failure parameters for 40CrMnSiB ...This paper investigates the three-dimensional crack propagation and damage evolution process of metallic column shells under internal explosive loading.The calibration of four typical failure parameters for 40CrMnSiB steel was conducted through experiments and subsequently applied to simulations.The numerical simulation results employing the four failure criteria were compared with the differences and similarities observed in freeze-recovery tests and ultra-high-speed tests.This analysis addressed the critical issue of determining failure criteria for the fracture of a metal shell under internal explosive loads.Building upon this foundation,the damage parameter D_(c),linked to the cumulative crack density,was defined based on the evolution characteristics of a substantial number of cracks.The relationship between the damage parameter and crack velocity over time was established,and the influence of the internal central pressure on the damage parameter and crack velocity was investigated.Variations in the fracture modes were found under different failure criteria,with the principal strain failure criterion proving to be the most effective for simulating 3D crack propagation in a pure shear fracture mode.Through statistical analysis of the shell penetration fracture radius data,it was determined that the fracture radius remained essentially constant during the crack evolution process and could be considered a constant.The propagation velocity of axial cracks ranged between 5300 m/s and 12600 m/s,surpassing the Rayleigh wave velocity of the shell material and decreasing linearly with time.The increase in shell damage exhibited an initial rapid phase,followed by deceleration,demonstrating accelerated damage during the propagation stage of the blast wave and decelerated damage after the arrival of the rarefaction wave.This study provides an effective approach for investigating crack propagation and damage evolution.The derived crack propagation and damage evolution law serves as a valuable reference for the development of crack velocity theory and the construction of shell damage evolution modes.展开更多
Non-cylindrical casings filled with explosives have undergone rapid development in warhead design and explosion control.The fragment spatial distribution of prismatic casings is more complex than that of traditional c...Non-cylindrical casings filled with explosives have undergone rapid development in warhead design and explosion control.The fragment spatial distribution of prismatic casings is more complex than that of traditional cylindrical casings.In this study,numerical and experimental investigations into the fragment spatial distribution of a prismatic casing were conducted.A new numerical method,which adds the Lagrangian marker points to the Eulerian grid,was proposed to track the multi-material interfaces and material dynamic fractures.Physical quantity mappings between the Lagrangian marker points and Eulerian grid were achieved by their topological relationship.Thereafter,the fragment spatial distributions of the prismatic casing with different fragment sizes,fragment shapes,and casing geometries were obtained using the numerical method.Moreover,fragment spatial distribution experiments were conducted on the prismatic casing with different fragment sizes and shapes,and the experimental data were compared with the numerical results.The effects of the fragment and casing geometry on the fragment spatial distributions were determined by analyzing the numerical results and experimental data.Finally,a formula including the casing geometry parameters was fitted to predict the fragment spatial distribution of the prismatic casing under internal explosive loading.展开更多
With the expansion of international terrorism and the potential threat of attacks against civil infrastructure,the dynamic response and failure modes of underground tunnels under explosive loads have become a prominen...With the expansion of international terrorism and the potential threat of attacks against civil infrastructure,the dynamic response and failure modes of underground tunnels under explosive loads have become a prominent research topic.The high cost and inherent danger associated with explosion experiments have limited current research on tunnel internal explosions,particularly in the context of scaled model tests of shield tunnels.This study presents a series of scaled model tests under 1g-condition simulating internal blast events within a shield tunnel based on the prototype of the Shantou Bay Tunnel,considering the influences of surrounding stratum and equivalent explosive yield.Three different TNT explosive yields are considered in the model tests,namely 0.2,0.4,and 1.0 kg.The model tests focus on the damage behavior and collapse modes of the shield tunnel lining under internal explosive loads.The model tests reveal that the shield tunnel is prone to damage at the joints of the tunnel crown and shoulder when subjected to internal explosive loads,with the upper half of the tunnel lining experiencing segment collapse,while the lower half remains largely undamaged.As the TNT equivalent increases,the damage area at the tunnel joints expands,and the number of segment failures in the upper half of the tunnel rises,transitioning from a damaged state to a collapsed state.The influence of“stratum-structure”interaction is investigated by comparing two models,one with overburden soil and the other positioned at the ground surface.The model tests reveal that the presence of soil pressure and confinement can significantly enhance the tunnel resistance to internal blast loads.Based on the observation of the model tests,five different damage modes of segment joints under internal explosion are proposed in this study.展开更多
基金financially supported by the National Natural Science Foundation of China (Grant No. 52278504)the Natural Science Foundation of Jiangsu Province (Grant No. BK20220141)。
文摘The afterburning of TNT and structural constraints in confined spaces significantly amplify the blast load,leading to severe structural damage. This study investigates the mechanisms underlying the enhanced dynamic response of reinforced concrete blast doors with four-sided restraints in confined space. Explosion tests with TNT charges ranging from 0.15 kg to 0.4 kg were conducted in a confined space,capturing overpressure loads and the dynamic response of the blast door. An internal explosion model incorporating the afterburning effect was developed using LS-DYNA software and validated against experimental data. The results reveal that the TNT afterburning effect amplifies both the initial peak overpressure and the quasi-static overpressure, resulting in increased deformation of the blast door.Within the 0.15-0.4 kg charge range, the initial overpressure peak and quasi-static overpressure increased by an average of 1.79 times and 2.21 times, respectively. Additionally, the afterburning effect enhanced the blast door's deflection by 177%. Compared to open-space scenarios, the cumulative deflection of the blast door due to repeated shock wave impacts is significantly greater in confined spaces. Furthermore, the quasi-static pressure arising from the structural constraints sustains the blast door's deflection at a high level.
基金supported by National Natural Science Foundation of China Innovation Group (Grant No.12221002)Beijing Natural Science Foundation (Grant No.L212018)。
文摘In order to study the blast damage effects of aviation kerosene storage tanks,the out-field explosion experiments of 8 m3fixed-roof tanks were carried out.The fragments,shock wave and fireball thermal radiation of the tank in the presence of bottom oil,half oil and full oil,as well as empty tank,were investigated under internal explosion by various TNT charge contents(1.8 kg,3.5 kg and 6.2 kg).The results showed that the tank roof was the only fragment produced,and the damage forms could be divided into three types.The increase of TNT charge content and oil volume enlarged the deformation of the tank,while the hole ratio presented a trend of increase first and then decrease.The H_r,maxand V_(max)values positively increased as increasing the TNT charge content and oil volume(from empty to half oil),but decreased in full oil.The Pmaxvalues had a progressive increase with the increment of TNT charge content,but not the case with the increase in oil volumes.The development of fireball was divided into three stages:tank roof‘towed'flame,jet flow flame tumbling and rising,and jet flow flame extinguishing.The Dmaxand Hf,maxvalues both increased as increasing TNT charge content and oil volumes.The oscillation phenomenon of fireball temperature was observed in the cooling process.The average temperature of fireball surface was positively correlated with TNT charge content,and negatively correlated with oil volumes.
基金supported by the National Natural Science Foundation of China (Grant No.12302437)Natural Science Foundation of Jiangsu Province (BK20230939)China Postdoctoral Science Foundation (2021M701710)。
文摘This paper investigates the three-dimensional crack propagation and damage evolution process of metallic column shells under internal explosive loading.The calibration of four typical failure parameters for 40CrMnSiB steel was conducted through experiments and subsequently applied to simulations.The numerical simulation results employing the four failure criteria were compared with the differences and similarities observed in freeze-recovery tests and ultra-high-speed tests.This analysis addressed the critical issue of determining failure criteria for the fracture of a metal shell under internal explosive loads.Building upon this foundation,the damage parameter D_(c),linked to the cumulative crack density,was defined based on the evolution characteristics of a substantial number of cracks.The relationship between the damage parameter and crack velocity over time was established,and the influence of the internal central pressure on the damage parameter and crack velocity was investigated.Variations in the fracture modes were found under different failure criteria,with the principal strain failure criterion proving to be the most effective for simulating 3D crack propagation in a pure shear fracture mode.Through statistical analysis of the shell penetration fracture radius data,it was determined that the fracture radius remained essentially constant during the crack evolution process and could be considered a constant.The propagation velocity of axial cracks ranged between 5300 m/s and 12600 m/s,surpassing the Rayleigh wave velocity of the shell material and decreasing linearly with time.The increase in shell damage exhibited an initial rapid phase,followed by deceleration,demonstrating accelerated damage during the propagation stage of the blast wave and decelerated damage after the arrival of the rarefaction wave.This study provides an effective approach for investigating crack propagation and damage evolution.The derived crack propagation and damage evolution law serves as a valuable reference for the development of crack velocity theory and the construction of shell damage evolution modes.
基金supported by the National Natural Science Foundation of China(Grant No.11822203and 11702026)。
文摘Non-cylindrical casings filled with explosives have undergone rapid development in warhead design and explosion control.The fragment spatial distribution of prismatic casings is more complex than that of traditional cylindrical casings.In this study,numerical and experimental investigations into the fragment spatial distribution of a prismatic casing were conducted.A new numerical method,which adds the Lagrangian marker points to the Eulerian grid,was proposed to track the multi-material interfaces and material dynamic fractures.Physical quantity mappings between the Lagrangian marker points and Eulerian grid were achieved by their topological relationship.Thereafter,the fragment spatial distributions of the prismatic casing with different fragment sizes,fragment shapes,and casing geometries were obtained using the numerical method.Moreover,fragment spatial distribution experiments were conducted on the prismatic casing with different fragment sizes and shapes,and the experimental data were compared with the numerical results.The effects of the fragment and casing geometry on the fragment spatial distributions were determined by analyzing the numerical results and experimental data.Finally,a formula including the casing geometry parameters was fitted to predict the fragment spatial distribution of the prismatic casing under internal explosive loading.
基金funding from the National Natural Foundation of China(Grant Nos.52178385 and 52020105002).
文摘With the expansion of international terrorism and the potential threat of attacks against civil infrastructure,the dynamic response and failure modes of underground tunnels under explosive loads have become a prominent research topic.The high cost and inherent danger associated with explosion experiments have limited current research on tunnel internal explosions,particularly in the context of scaled model tests of shield tunnels.This study presents a series of scaled model tests under 1g-condition simulating internal blast events within a shield tunnel based on the prototype of the Shantou Bay Tunnel,considering the influences of surrounding stratum and equivalent explosive yield.Three different TNT explosive yields are considered in the model tests,namely 0.2,0.4,and 1.0 kg.The model tests focus on the damage behavior and collapse modes of the shield tunnel lining under internal explosive loads.The model tests reveal that the shield tunnel is prone to damage at the joints of the tunnel crown and shoulder when subjected to internal explosive loads,with the upper half of the tunnel lining experiencing segment collapse,while the lower half remains largely undamaged.As the TNT equivalent increases,the damage area at the tunnel joints expands,and the number of segment failures in the upper half of the tunnel rises,transitioning from a damaged state to a collapsed state.The influence of“stratum-structure”interaction is investigated by comparing two models,one with overburden soil and the other positioned at the ground surface.The model tests reveal that the presence of soil pressure and confinement can significantly enhance the tunnel resistance to internal blast loads.Based on the observation of the model tests,five different damage modes of segment joints under internal explosion are proposed in this study.
