2024 Vol. 44, No. 10
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2024, 44(10): 101001.
doi: 10.11883/bzycj-2024-0297
Abstract:
The mechanical properties of materials or structures under dynamic compression-shear combined loading conditions significantly influence their engineering applications. However, existing experimental methodologies for dynamic combined loading confront challenges, such as the difficulty in synchronously applying compression and shear waves to test specimens, in addition to the high cost of experimental equipment. This study introduces a novel experimental technique that utilizes compression-torsion coupling metamaterials for the conversion of stress waves, enabling synchronous dynamic compression-shear combined loading on a one-dimensional Hopkinson pressure bar. This technique offers several advantages, including precise load synchronization, a controllable shear-compression ratio, simplicity, convenience, and low cost. A detailed discussion is presented on the issue of triangular torsion signals that arise when the amplitude of torsional waves converted from compression-torsion metamaterials reaches considerable levels, coupled with insufficient inertial confinement in the transmission bar of the split Hopkinson pressure bar system. Additionally, corresponding solutions to this issue are proposed. Experimental tests were conducted on three materials with distinct yield stresses: titanium, 304 stainless steel, and 316L stainless steel, validating the effectiveness of this experimental technique. Furthermore, leveraging finite element models, an in-depth analysis was conducted on the influence of the geometric parameters of the compression-torsion coupling metamaterials on their compression-torsion coefficients and load-bearing capacities. By integrating these findings with experimental results, the applicability of this experimental technique was discussed, predicting its capability to test materials with strengths up to approximately 1 GPa and to apply shear-compression ratios up to 1.18 to specimens, providing a reference for its application in a broader range of fields. This innovative integration of metamaterials with traditional experimental equipment opens up new avenues for realizing more complex dynamic loading experiments.
The mechanical properties of materials or structures under dynamic compression-shear combined loading conditions significantly influence their engineering applications. However, existing experimental methodologies for dynamic combined loading confront challenges, such as the difficulty in synchronously applying compression and shear waves to test specimens, in addition to the high cost of experimental equipment. This study introduces a novel experimental technique that utilizes compression-torsion coupling metamaterials for the conversion of stress waves, enabling synchronous dynamic compression-shear combined loading on a one-dimensional Hopkinson pressure bar. This technique offers several advantages, including precise load synchronization, a controllable shear-compression ratio, simplicity, convenience, and low cost. A detailed discussion is presented on the issue of triangular torsion signals that arise when the amplitude of torsional waves converted from compression-torsion metamaterials reaches considerable levels, coupled with insufficient inertial confinement in the transmission bar of the split Hopkinson pressure bar system. Additionally, corresponding solutions to this issue are proposed. Experimental tests were conducted on three materials with distinct yield stresses: titanium, 304 stainless steel, and 316L stainless steel, validating the effectiveness of this experimental technique. Furthermore, leveraging finite element models, an in-depth analysis was conducted on the influence of the geometric parameters of the compression-torsion coupling metamaterials on their compression-torsion coefficients and load-bearing capacities. By integrating these findings with experimental results, the applicability of this experimental technique was discussed, predicting its capability to test materials with strengths up to approximately 1 GPa and to apply shear-compression ratios up to 1.18 to specimens, providing a reference for its application in a broader range of fields. This innovative integration of metamaterials with traditional experimental equipment opens up new avenues for realizing more complex dynamic loading experiments.
2024, 44(10): 101401.
doi: 10.11883/bzycj-2023-0472
Abstract:
It is of great scientific significance and application value to study the anti-penetration performance of continuous fiber-reinforced high-porosity composites. First, the ballistic penetration experiments of 20 mm thick continuous fiber-reinforced high-porosity composites were carried out by using two-stage light gas gun firing Q235 steel projectiles of diameter 4.5 mm. Based on the analysis of the initial and final velocities of bullet penetration, the ballistic limit of the material is obtained. By observing the damage patterns of the target plate, these patterns are divided into three types from low to high according to the initial velocity of the projectiles: back-crack type, back-burst type and penetrated type. The anti-penetration performance of this composite material is compared with other materials by specific energy absorption, showing that the anti-penetration performance of the composite against low-speed penetration up to 600 m/s is better than those of steel, aluminum, Kevlar and glass fiber composite. Then, an orthogonal anisotropic continuum damage constitutive model is proposed for the continuous fiber-reinforced high-porosity composites. This constitutive model is written as a subroutine and embedded in the finite element software by secondary development. On this basis, the finite element simulations of ballistic penetrations of continuous fiber reinforced high-porosity composites are conducted. The validity of the constitutive and finite element models is verified by comparing the final velocity, ballistic limit and damage range of the back surface obtained from experiment and simulation. Furthermore, the damage mechanism of the penetration process is analyzed by observing the shape of the bullet hole, stress distribution and damage distribution obtained from the finite element simulation. The results show that the formation of the bullet hole during the penetration of spherical projectile is caused by shear damage, the debonding of fiber and matrix is caused by the combined action of compression and shear, the delamination damage of the target plate is caused by the tension wave created by the reflection of compression wave, and the fiber breakage belongs to tension damage. Besides, the kinetic energy, internal energy and their proportion to the kinetic energy change of the bullet are compared with the initial velocity. It is pointed out that most of the kinetic energy of the projectile is transformed into the kinetic energy of the fragment of target plates and the plastic deformation energy of the projectile. The research results provide a reference for the multifunctional integration of these composite materials in heat protection, penetration protection and load bearing.
It is of great scientific significance and application value to study the anti-penetration performance of continuous fiber-reinforced high-porosity composites. First, the ballistic penetration experiments of 20 mm thick continuous fiber-reinforced high-porosity composites were carried out by using two-stage light gas gun firing Q235 steel projectiles of diameter 4.5 mm. Based on the analysis of the initial and final velocities of bullet penetration, the ballistic limit of the material is obtained. By observing the damage patterns of the target plate, these patterns are divided into three types from low to high according to the initial velocity of the projectiles: back-crack type, back-burst type and penetrated type. The anti-penetration performance of this composite material is compared with other materials by specific energy absorption, showing that the anti-penetration performance of the composite against low-speed penetration up to 600 m/s is better than those of steel, aluminum, Kevlar and glass fiber composite. Then, an orthogonal anisotropic continuum damage constitutive model is proposed for the continuous fiber-reinforced high-porosity composites. This constitutive model is written as a subroutine and embedded in the finite element software by secondary development. On this basis, the finite element simulations of ballistic penetrations of continuous fiber reinforced high-porosity composites are conducted. The validity of the constitutive and finite element models is verified by comparing the final velocity, ballistic limit and damage range of the back surface obtained from experiment and simulation. Furthermore, the damage mechanism of the penetration process is analyzed by observing the shape of the bullet hole, stress distribution and damage distribution obtained from the finite element simulation. The results show that the formation of the bullet hole during the penetration of spherical projectile is caused by shear damage, the debonding of fiber and matrix is caused by the combined action of compression and shear, the delamination damage of the target plate is caused by the tension wave created by the reflection of compression wave, and the fiber breakage belongs to tension damage. Besides, the kinetic energy, internal energy and their proportion to the kinetic energy change of the bullet are compared with the initial velocity. It is pointed out that most of the kinetic energy of the projectile is transformed into the kinetic energy of the fragment of target plates and the plastic deformation energy of the projectile. The research results provide a reference for the multifunctional integration of these composite materials in heat protection, penetration protection and load bearing.
2024, 44(10): 101402.
doi: 10.11883/bzycj-2023-0424
Abstract:
In order to investigate the dynamic compression behavior of carbon nanotubes reinforced concrete under impact loading, the impact compression tests were carried out by using a split Hopkinson pressure bar (SHPB) test device with a diameter of 100 mm. The impact velocities in the SHPB tests were about 6.8, 7.8, 8.8, 9.8 and 10.8 m/s, respectively. The contents of carbon nanotubes in concrete (as a percentage of cement mass) were 0% (i.e. ordinary concrete, as a baseline of comparison), 0.10%, 0.20%, 0.30% and 0.40%, respectively. Then, based on the test results, the evolution laws of dynamic compressive strength, compression deformation, and energy dissipation characteristics of concrete under different impact velocities and carbon nanotubes contents were compared and analyzed. The experimental results show that the dynamic strength characteristics of carbon nanotubes reinforced concrete have significant loading rate sensitivity. The dynamic compressive strength and dynamic enhancement factor show linear positive correlations with impact velocity. When the loading level remains the same, the dynamic compressive strength increases first and then decreases slightly with the increase of carbon nanotubes content, and the growth rate can reach 23.7% compared to ordinary concrete. The variation characteristics of ultimate strain and impact toughness of carbon nanotubes reinforced concrete are similar, which gradually increase with the increase of impact velocity, and have a certain impact velocity strengthening effect, but there is no obvious linear relationship with the impact velocity. Toughness is a comprehensive reflection of material strength and deformation. Therefore, at the same loading level, when the content of carbon nanotubes was 0.30%, the impact toughness of concrete achieved a relative maximum, being about 10% higher than that of ordinary concrete. The appropriate addition of carbon nanotubes can effectively enhance the integrity and compactness of the internal structure of concrete, thereby improving its dynamic mechanical properties and energy dissipation performance.
In order to investigate the dynamic compression behavior of carbon nanotubes reinforced concrete under impact loading, the impact compression tests were carried out by using a split Hopkinson pressure bar (SHPB) test device with a diameter of 100 mm. The impact velocities in the SHPB tests were about 6.8, 7.8, 8.8, 9.8 and 10.8 m/s, respectively. The contents of carbon nanotubes in concrete (as a percentage of cement mass) were 0% (i.e. ordinary concrete, as a baseline of comparison), 0.10%, 0.20%, 0.30% and 0.40%, respectively. Then, based on the test results, the evolution laws of dynamic compressive strength, compression deformation, and energy dissipation characteristics of concrete under different impact velocities and carbon nanotubes contents were compared and analyzed. The experimental results show that the dynamic strength characteristics of carbon nanotubes reinforced concrete have significant loading rate sensitivity. The dynamic compressive strength and dynamic enhancement factor show linear positive correlations with impact velocity. When the loading level remains the same, the dynamic compressive strength increases first and then decreases slightly with the increase of carbon nanotubes content, and the growth rate can reach 23.7% compared to ordinary concrete. The variation characteristics of ultimate strain and impact toughness of carbon nanotubes reinforced concrete are similar, which gradually increase with the increase of impact velocity, and have a certain impact velocity strengthening effect, but there is no obvious linear relationship with the impact velocity. Toughness is a comprehensive reflection of material strength and deformation. Therefore, at the same loading level, when the content of carbon nanotubes was 0.30%, the impact toughness of concrete achieved a relative maximum, being about 10% higher than that of ordinary concrete. The appropriate addition of carbon nanotubes can effectively enhance the integrity and compactness of the internal structure of concrete, thereby improving its dynamic mechanical properties and energy dissipation performance.
2024, 44(10): 101403.
doi: 10.11883/bzycj-2024-0017
Abstract:
The weathering effect can lead to the development of pores in rock material, which affects its engineering properties seriously. Therefore, studying the influence of the weathering effect on the mechanical properties and anti-penetration properties of granite is of great significance to evaluate the damage effectiveness of penetration warheads and analyze the protection capability of underground facilities. The two kinds of granite with different weathering degrees were selected to systematically investigate their physical properties, static/dynamic compressive properties, and anti-penetration properties with the experiment methods, such as the X-ray diffraction (XRD) test, the static uniaxial compression test, the static triaxial compression test, the dynamic uniaxial compression test, the dynamic triaxial compression test, and the two-stage light gas gun test. Finally, the results indicate that the weathering effect can cause a decrease in biotite and microcline, an increase in porosity, loose internal structure, and obvious defects in granite, based on the X-ray diffraction analysis technique. Besides, the weathering effect can also lead to deterioration in granite’s compressive strength, weakened strain rate effect, and the shift of the failure mode from brittle failure to weak shear failure. Under static and dynamic triaxial compression, as for the two kinds of weathered granite, static and dynamic compressive strength rises significantly with the increase of confining pressure, while moderately weathered granite is more sensitive to confining pressure, compared with the slightly weathered granite. Under the condition of high-speed penetration, the speed varying from 873 m/s to1040 m/s, there is little difference in anti-penetration performance for the two kinds of weathered granite, in which case both of the non-dimensional penetration depths are generally no more than three times the length of the projectiles. Moreover, no obvious penetration trajectory zones exit in weathered granite targets while there are significant crushed zones around the projectiles, the length of which can reach up to 5−8 times the diameter of the projectiles.
The weathering effect can lead to the development of pores in rock material, which affects its engineering properties seriously. Therefore, studying the influence of the weathering effect on the mechanical properties and anti-penetration properties of granite is of great significance to evaluate the damage effectiveness of penetration warheads and analyze the protection capability of underground facilities. The two kinds of granite with different weathering degrees were selected to systematically investigate their physical properties, static/dynamic compressive properties, and anti-penetration properties with the experiment methods, such as the X-ray diffraction (XRD) test, the static uniaxial compression test, the static triaxial compression test, the dynamic uniaxial compression test, the dynamic triaxial compression test, and the two-stage light gas gun test. Finally, the results indicate that the weathering effect can cause a decrease in biotite and microcline, an increase in porosity, loose internal structure, and obvious defects in granite, based on the X-ray diffraction analysis technique. Besides, the weathering effect can also lead to deterioration in granite’s compressive strength, weakened strain rate effect, and the shift of the failure mode from brittle failure to weak shear failure. Under static and dynamic triaxial compression, as for the two kinds of weathered granite, static and dynamic compressive strength rises significantly with the increase of confining pressure, while moderately weathered granite is more sensitive to confining pressure, compared with the slightly weathered granite. Under the condition of high-speed penetration, the speed varying from 873 m/s to
2024, 44(10): 101404.
doi: 10.11883/bzycj-2024-0021
Abstract:
Terrorist attacks and local wars occur frequently, which makes the risk of buildings subjected to multiple explosions increasing. Most of the existing research focuses on the single explosion scenario, and there are few studies on the damage effect of reinforced concrete structures under multiple explosions. In order to study the damage effect of reinforcement concrete beams under secondary explosion and offset the shortcomings of the existing research, relevant numerical analysis was carried out. The damage parameters of the K&C concrete constitutive model were modified firstly. And the arbitrary Lagrangian-Eulerian method for fluid-structure interaction was used to simulate the secondary explosion experiment of reinforced concrete beam with the full restart function of LS-DYNA. The numerical analysis results were well consistent with the test results, verifying the effectiveness of the simulation method and the modified constitutive model. On this basis, the secondary explosion simulation conditions were expanded. The effects of various parameters, including scaled distance, concrete compressive strength, longitudinal reinforcement ratio and transverse reinforcement details, on the damage effect of typical size reinforcement concrete beams under secondary explosion were further analyzed. The results show that due to the compressive membrane action of reinforcement concrete beam, keeping the total equivalent TNT weight of the explosion unchanged, the damage of RC component caused by one single explosion is more serious than the cumulative damage caused by two successive explosions. The concrete compressive strength has a more significant effect on the blast resistance performance of RC beams under secondary explosion, the higher the concrete strength, the lower the damage degree of the beam under the secondary explosion. Increasing the longitudinal reinforcement ratio has no obvious effect on improving the blast resistance performance of the beam and reducing the transverse reinforcement spacing can effectively decrease the shear failure degree of reinforcement concrete beam which makes the blast resistance performance of RC beams under secondary explosion and near explosion improved. The iso-damage curves of reinforcement concrete beams with two different design parameters are further calculated and the corresponding damage degree zoning maps are established.
Terrorist attacks and local wars occur frequently, which makes the risk of buildings subjected to multiple explosions increasing. Most of the existing research focuses on the single explosion scenario, and there are few studies on the damage effect of reinforced concrete structures under multiple explosions. In order to study the damage effect of reinforcement concrete beams under secondary explosion and offset the shortcomings of the existing research, relevant numerical analysis was carried out. The damage parameters of the K&C concrete constitutive model were modified firstly. And the arbitrary Lagrangian-Eulerian method for fluid-structure interaction was used to simulate the secondary explosion experiment of reinforced concrete beam with the full restart function of LS-DYNA. The numerical analysis results were well consistent with the test results, verifying the effectiveness of the simulation method and the modified constitutive model. On this basis, the secondary explosion simulation conditions were expanded. The effects of various parameters, including scaled distance, concrete compressive strength, longitudinal reinforcement ratio and transverse reinforcement details, on the damage effect of typical size reinforcement concrete beams under secondary explosion were further analyzed. The results show that due to the compressive membrane action of reinforcement concrete beam, keeping the total equivalent TNT weight of the explosion unchanged, the damage of RC component caused by one single explosion is more serious than the cumulative damage caused by two successive explosions. The concrete compressive strength has a more significant effect on the blast resistance performance of RC beams under secondary explosion, the higher the concrete strength, the lower the damage degree of the beam under the secondary explosion. Increasing the longitudinal reinforcement ratio has no obvious effect on improving the blast resistance performance of the beam and reducing the transverse reinforcement spacing can effectively decrease the shear failure degree of reinforcement concrete beam which makes the blast resistance performance of RC beams under secondary explosion and near explosion improved. The iso-damage curves of reinforcement concrete beams with two different design parameters are further calculated and the corresponding damage degree zoning maps are established.
2024, 44(10): 101405.
doi: 10.11883/bzycj-2024-0077
Abstract:
In order to study the anti-explosion ability of reinforced masonry wall and the reinforcement performance of polyurea on the wall, LS-DYNA software was used to numerically simulate the dynamic response of unreinforced masonry wall, reinforced masonry wall, and masonry wall strengthened with polyurea respectively. The anti-gas explosion performance of different walls under gas explosion load with peak value of 5, 10, 20 and 30 kPa was obtained. The reinforcing effect of vertical reinforcement in ash joint and polyurea were compared and analyzed. The results show that: (1) The anti-gas explosion capability of the unreinforced wall is relatively weak, which generally causes irreparable damage under the load of 20 kPa and collapses under the load of 30 kPa. (2) The explosion resistance of the masonry wall can be enhanced by the vertical displacement of rebar in the ash joint and the spraying of polyurea on the wall surface. Under the load of 20 kPa, the peak displacement at mid-span of each reinforced wall is smaller than that of the unreinforced wall, and the damage is lighter, which is repairable. Among them, the anti-explosion effect of double-sided spraying polyurea on unreinforced wall surface is the best, and there is no collapse damage under the load of 30 kPa. The reinforcing effect of vertical reinforcement in ash joint and polyurea spraying on the back surface are the second. (3) The three groups of reinforced walls with polyurea can all withstand 30 kPa gas explosion load. Cracks occur in the middle of the wall strengthened by spraying on the explosive side, fragments splash, the mid-span peak displacement is the largest. Local damage occurs at both ends of the wall strengthened by back side and double-sided spraying, and the walls are basically complete, and the mid-span peak displacement of the wall strengthened by double-side spraying is the smallest. It is shown that spraying polyurea on both sides on the basis of vertical reinforcement in ash joint has the best explosion resistance effect, and can also bear greater gas explosion load. The research results can provide reference for the reinforcement of reinforced masonry wall against gas explosion.
In order to study the anti-explosion ability of reinforced masonry wall and the reinforcement performance of polyurea on the wall, LS-DYNA software was used to numerically simulate the dynamic response of unreinforced masonry wall, reinforced masonry wall, and masonry wall strengthened with polyurea respectively. The anti-gas explosion performance of different walls under gas explosion load with peak value of 5, 10, 20 and 30 kPa was obtained. The reinforcing effect of vertical reinforcement in ash joint and polyurea were compared and analyzed. The results show that: (1) The anti-gas explosion capability of the unreinforced wall is relatively weak, which generally causes irreparable damage under the load of 20 kPa and collapses under the load of 30 kPa. (2) The explosion resistance of the masonry wall can be enhanced by the vertical displacement of rebar in the ash joint and the spraying of polyurea on the wall surface. Under the load of 20 kPa, the peak displacement at mid-span of each reinforced wall is smaller than that of the unreinforced wall, and the damage is lighter, which is repairable. Among them, the anti-explosion effect of double-sided spraying polyurea on unreinforced wall surface is the best, and there is no collapse damage under the load of 30 kPa. The reinforcing effect of vertical reinforcement in ash joint and polyurea spraying on the back surface are the second. (3) The three groups of reinforced walls with polyurea can all withstand 30 kPa gas explosion load. Cracks occur in the middle of the wall strengthened by spraying on the explosive side, fragments splash, the mid-span peak displacement is the largest. Local damage occurs at both ends of the wall strengthened by back side and double-sided spraying, and the walls are basically complete, and the mid-span peak displacement of the wall strengthened by double-side spraying is the smallest. It is shown that spraying polyurea on both sides on the basis of vertical reinforcement in ash joint has the best explosion resistance effect, and can also bear greater gas explosion load. The research results can provide reference for the reinforcement of reinforced masonry wall against gas explosion.
2024, 44(10): 101406.
doi: 10.11883/bzycj-2024-0041
Abstract:
To investigate the velocity distribution characteristics of elliptical section warhead (ECSW) fragments under different initiation modes, a numerical simulation model was established for five ECSWs with different shape ratios. Numerical simulations were conducted to investigate the velocity distribution and energy output characteristics of fragments from ECSW under five different initiation modes: central single-point initiation, dual-point initiation at the midpoint of the minor (or major) axis, four-point initiation at the midpoint of the major and minor axes, as well as surface-initiated detonation. The research findings suggest that the maximum radial velocity of fragments follows a consistent logarithmic growth pattern in the radial direction across various initiation modes, increasing from the major axis to the minor axis direction. With an increase in the shape ratio, the difference in fragment velocities between the major and minor axis directions gradually decreases. However, the maximum velocity profiles of fragments from elliptical section warheads exhibit noticeable differences in average velocities under different initiation modes. Surface-initiated detonation produces the highest average radial velocity, whereas single-point initiation leads to the lowest. As the number of initiation points increases, the overall average fragment velocity on the maximum velocity profile gradually rises. In the axial direction, the influence of rarefaction waves leads to the maximum fragment velocities occurring near the 1/4 position from the non-initiating end at different azimuthal angles. Initiation points along the minor axis enhance the fragment velocity in the major axis direction near the initiating end compared to initiating points along the major axis. However, there are no significant variations in the axial velocity distribution of fragments in the minor axis direction. The different initiation modes have negligible effects on the energy output characteristics of elliptical section charges. Approximately 27% of the charge energy is converted into shell kinetic energy, while 50% is dissipated through casing fracture deformation and air shock wave propagation.
To investigate the velocity distribution characteristics of elliptical section warhead (ECSW) fragments under different initiation modes, a numerical simulation model was established for five ECSWs with different shape ratios. Numerical simulations were conducted to investigate the velocity distribution and energy output characteristics of fragments from ECSW under five different initiation modes: central single-point initiation, dual-point initiation at the midpoint of the minor (or major) axis, four-point initiation at the midpoint of the major and minor axes, as well as surface-initiated detonation. The research findings suggest that the maximum radial velocity of fragments follows a consistent logarithmic growth pattern in the radial direction across various initiation modes, increasing from the major axis to the minor axis direction. With an increase in the shape ratio, the difference in fragment velocities between the major and minor axis directions gradually decreases. However, the maximum velocity profiles of fragments from elliptical section warheads exhibit noticeable differences in average velocities under different initiation modes. Surface-initiated detonation produces the highest average radial velocity, whereas single-point initiation leads to the lowest. As the number of initiation points increases, the overall average fragment velocity on the maximum velocity profile gradually rises. In the axial direction, the influence of rarefaction waves leads to the maximum fragment velocities occurring near the 1/4 position from the non-initiating end at different azimuthal angles. Initiation points along the minor axis enhance the fragment velocity in the major axis direction near the initiating end compared to initiating points along the major axis. However, there are no significant variations in the axial velocity distribution of fragments in the minor axis direction. The different initiation modes have negligible effects on the energy output characteristics of elliptical section charges. Approximately 27% of the charge energy is converted into shell kinetic energy, while 50% is dissipated through casing fracture deformation and air shock wave propagation.
2024, 44(10): 101407.
doi: 10.11883/bzycj-2023-0455
Abstract:
Explosive welding production in a vacuum explosion containment vessel can not only restrict the shock wave and noise generated by explosive explosion in a certain space range, but also effectively improve the quality of explosive welding products. Meanwhile, it also alleviates the problems of unstable product quality and rainy season shutdown caused by the influence of weather and climate during explosive welding production, which is an invention that can promote the development of the explosive processing industry. In order to develop a super large vacuum explosion containment vessel for explosive welding, it is necessary to explore the internal blast load and dynamic response of vacuum explosion containment vessel with sand covered for explosive welding. In order to meet the requirements of the experiment, a 0.55 m3 small cylindrical vacuum explosion containment vessel with the cap covered by a certain thickness of sand was designed, and a series of vacuum explosion experiments were carried out in it. At the same time, using the AUTODYN finite element analysis program, the numerical simulation analysis of the corresponding experimental groups is carried out. The evolution of shock wave inside the container, the distribution of blast load, the dynamic response of the structure, and the mechanism of sand covering on the end of the container on the damping of the plate structure are explored in depth. By analyzing the results of experiment and numerical simulation, it is concluded that the peak value of the second impulse of the time-history curve of the blast load in the explosion containment vessel is obviously higher than that of the first impulse, and the superposition and reflection of the shock wave always occur in the inner wall of the cover. With the decrease of vacuum degree inside the container, the peak value of the blast load is weakened obviously. According to the time-history curves of blast load and dynamic strain calculated by the numerical simulation, the dynamic response of the container cover is divided into four development phases: step-up phase, impulse follower phase, inertial lag phase and static pressure stabilization phase. With the decrease of vacuum degree, the amplitude of dynamic response is weakened obviously. With the increase of the thickness of sand cover, the dynamic response of explosion vessel is gradually weakened. Ultimately, it is concluded that reducing the environmental pressure inside the vessel and increasing the thickness of the sand covered on the cap of the container can be used as an effective method to reduce the forced vibration of the explosion containment vessel. The conclusions of the study are useful for the structural design of super large vacuum explosion containment vessels.
Explosive welding production in a vacuum explosion containment vessel can not only restrict the shock wave and noise generated by explosive explosion in a certain space range, but also effectively improve the quality of explosive welding products. Meanwhile, it also alleviates the problems of unstable product quality and rainy season shutdown caused by the influence of weather and climate during explosive welding production, which is an invention that can promote the development of the explosive processing industry. In order to develop a super large vacuum explosion containment vessel for explosive welding, it is necessary to explore the internal blast load and dynamic response of vacuum explosion containment vessel with sand covered for explosive welding. In order to meet the requirements of the experiment, a 0.55 m3 small cylindrical vacuum explosion containment vessel with the cap covered by a certain thickness of sand was designed, and a series of vacuum explosion experiments were carried out in it. At the same time, using the AUTODYN finite element analysis program, the numerical simulation analysis of the corresponding experimental groups is carried out. The evolution of shock wave inside the container, the distribution of blast load, the dynamic response of the structure, and the mechanism of sand covering on the end of the container on the damping of the plate structure are explored in depth. By analyzing the results of experiment and numerical simulation, it is concluded that the peak value of the second impulse of the time-history curve of the blast load in the explosion containment vessel is obviously higher than that of the first impulse, and the superposition and reflection of the shock wave always occur in the inner wall of the cover. With the decrease of vacuum degree inside the container, the peak value of the blast load is weakened obviously. According to the time-history curves of blast load and dynamic strain calculated by the numerical simulation, the dynamic response of the container cover is divided into four development phases: step-up phase, impulse follower phase, inertial lag phase and static pressure stabilization phase. With the decrease of vacuum degree, the amplitude of dynamic response is weakened obviously. With the increase of the thickness of sand cover, the dynamic response of explosion vessel is gradually weakened. Ultimately, it is concluded that reducing the environmental pressure inside the vessel and increasing the thickness of the sand covered on the cap of the container can be used as an effective method to reduce the forced vibration of the explosion containment vessel. The conclusions of the study are useful for the structural design of super large vacuum explosion containment vessels.
2024, 44(10): 101408.
doi: 10.11883/bzycj-2023-0465
Abstract:
To investigate the influence of typical metal powders on the shock wave effect and thermal damage performance of fuel air explosive (FAE), the explosion characteristics, flame structure and temperature distribution characteristics of epoxypropane (PO) with different types and contents of metal powders were experimentally studied using a 20 L spherical liquid explosion test system. The temperature field of explosion flame was reconstructed by the colorimetric temperature measurement method with a high-speed camera, which is based on the gray-body radiation theory and a self-written python code. The tungsten lamp was used to calibrate the measuring accuracy of the temperature mapping system, and the fitting relationship between the temperatures and the gray values of the high-speed images is derived to obtain the conversion coefficient. The experimental results show that the optimal mass concentration of pure PO was 780 g/m3, both the explosion overpressure (∆pmax) and the explosion pressure rise rate ((dp/dt)max) reached the maximum, ∆pmax=0.799 MPa and (dp/dt)max=52.438 MPa/s, respectively. The maximum explosion overpressure, maximum explosion pressure rise rate and maximum average temperature of PO added with Al, Ti and Mg powders all increase with the increase of mass ratios (I), while the trend of maximum pressure rise time is opposite. The variation rules of the maximum explosion overpressure and maximum average temperature are consistent, the order of their values is: Al/PO, Mg/PO, Ti/PO. When I=40%, the maximum explosion overpressure value of the three solid-liquid mixed fuels increases by 12.00%, 8.41% and 11.54%, respectively, compared with pure PO. In addition, the variation rules of the maximum explosion pressure rise rate and the combustion rate are consistent, the order of their values is: Al/PO, Mg/PO, Ti/PO. When I=40%, the maximum explosion pressure rise rate value of the three solid-liquid mixed fuels increases by 41.91%, 39.60% and 45.29%, respectively, compared with the pure PO. The results indicate that different high-energy metal powders have varied advantages in improving the explosion performance of PO, so metal powders should be appropriately selected as energetic additives according to the damage performance index in the formulation design of FAE.
To investigate the influence of typical metal powders on the shock wave effect and thermal damage performance of fuel air explosive (FAE), the explosion characteristics, flame structure and temperature distribution characteristics of epoxypropane (PO) with different types and contents of metal powders were experimentally studied using a 20 L spherical liquid explosion test system. The temperature field of explosion flame was reconstructed by the colorimetric temperature measurement method with a high-speed camera, which is based on the gray-body radiation theory and a self-written python code. The tungsten lamp was used to calibrate the measuring accuracy of the temperature mapping system, and the fitting relationship between the temperatures and the gray values of the high-speed images is derived to obtain the conversion coefficient. The experimental results show that the optimal mass concentration of pure PO was 780 g/m3, both the explosion overpressure (∆pmax) and the explosion pressure rise rate ((dp/dt)max) reached the maximum, ∆pmax=0.799 MPa and (dp/dt)max=52.438 MPa/s, respectively. The maximum explosion overpressure, maximum explosion pressure rise rate and maximum average temperature of PO added with Al, Ti and Mg powders all increase with the increase of mass ratios (I), while the trend of maximum pressure rise time is opposite. The variation rules of the maximum explosion overpressure and maximum average temperature are consistent, the order of their values is: Al/PO, Mg/PO, Ti/PO. When I=40%, the maximum explosion overpressure value of the three solid-liquid mixed fuels increases by 12.00%, 8.41% and 11.54%, respectively, compared with pure PO. In addition, the variation rules of the maximum explosion pressure rise rate and the combustion rate are consistent, the order of their values is: Al/PO, Mg/PO, Ti/PO. When I=40%, the maximum explosion pressure rise rate value of the three solid-liquid mixed fuels increases by 41.91%, 39.60% and 45.29%, respectively, compared with the pure PO. The results indicate that different high-energy metal powders have varied advantages in improving the explosion performance of PO, so metal powders should be appropriately selected as energetic additives according to the damage performance index in the formulation design of FAE.
2024, 44(10): 102101.
doi: 10.11883/bzycj-2023-0199
Abstract:
As a typical characteristic of fireball phenomena, thermal radiation plays an important role in damage assessments. Up to now, many studies of thermal radiation using theoretical, numerical, and experimental methods have been carried out and empirical formulas in forms of yield or density are constructed to feature the extremal characteristic of fireball thermal radiation. However, due to the combined action of radiation free path (RFP) and fireball characteristic length (FCL), it is difficult to identify these formula’s application scope, and further theoretical studies are needed to take the scale effect (SE) into account. By radiation heat conduction approximation model under optical thickness assumption, scale effect similarity parameter (SESP) was theoretically derived and its scope of application is further verified by high-precision numerical method. The numerical code is developed within a framework of Euler method, and adaptive mesh refinement method is employed to improve the precision in the radiation front. The results of theoretical analysis show that SESP is consistent with existed conclusions regarding the thermal radiation of fireball at different altitudes, and it can be applied to the analysis of laboratory scale fireball. Meanwhile, numerical results also show that both scale effects at different altitudes and laboratory scale can be characterized by SESP.
As a typical characteristic of fireball phenomena, thermal radiation plays an important role in damage assessments. Up to now, many studies of thermal radiation using theoretical, numerical, and experimental methods have been carried out and empirical formulas in forms of yield or density are constructed to feature the extremal characteristic of fireball thermal radiation. However, due to the combined action of radiation free path (RFP) and fireball characteristic length (FCL), it is difficult to identify these formula’s application scope, and further theoretical studies are needed to take the scale effect (SE) into account. By radiation heat conduction approximation model under optical thickness assumption, scale effect similarity parameter (SESP) was theoretically derived and its scope of application is further verified by high-precision numerical method. The numerical code is developed within a framework of Euler method, and adaptive mesh refinement method is employed to improve the precision in the radiation front. The results of theoretical analysis show that SESP is consistent with existed conclusions regarding the thermal radiation of fireball at different altitudes, and it can be applied to the analysis of laboratory scale fireball. Meanwhile, numerical results also show that both scale effects at different altitudes and laboratory scale can be characterized by SESP.
2024, 44(10): 103301.
doi: 10.11883/bzycj-2022-0309
Abstract:
The accurate prediction of the critical penetration speed of a rigid body is a key issue in the study of high-strength steel projectile penetration into concrete targets at high velocities. This paper conducts experimental research on the penetration of C40 concrete targets by high-strength steel (G50) ogive-nosed long rod projectiles at the velocities of1010 to 1660 m/s using a two-stage light gas gun, obtaining experimental data on the critical penetration velocity and penetration depth of the rigid body. Theoretical analysis of the critical penetration velocity of the rigid body and the penetration depth considering the projectile head erosion is also carried out, and the following conclusions are drawn: (1) the interval of the critical penetration velocity for G50 ogive-nosed long rod projectiles penetrating C40 concrete targets is 1320 to 1520 m/s; (2) based on existing penetration models, a new theoretical model for the critical penetration velocity of the rigid body was established, and the calculated results of the model are in good agreement with the experimental results of this paper and the literature; (3) a penetration depth model considering head erosion was established, which also matches the experimental results well; (4) the yield strength of the projectile has a significant effect on the critical penetration velocity of the rigid body, the unconfined compressive strength of the target has a minor effect on the critical penetration velocity, and the shape coefficient and size of the projectile before the experiment have no significant effect on the critical penetration velocity.
The accurate prediction of the critical penetration speed of a rigid body is a key issue in the study of high-strength steel projectile penetration into concrete targets at high velocities. This paper conducts experimental research on the penetration of C40 concrete targets by high-strength steel (G50) ogive-nosed long rod projectiles at the velocities of
2024, 44(10): 103302.
doi: 10.11883/bzycj-2022-0310
Abstract:
In order to study the influence of projectile material parameters (mainly strength, toughness, etc.) on the penetration depth of hypervelocity penetrating concrete targets, experiments of 93W alloy column-shaped projectiles with different material properties penetrating concrete targets at2300 –3600 m/s were carried out on a 57/10 two-stage light gas gun. The projectile velocity was measured by a laser velocimetry system, of which the uncertainty is less than 1%. The experimental data of penetration depth and residual projectile length of different projectiles were obtained by computed tomography (CT) diagnosis technology, which can achieve a measurement accuracy of 0.1 mm. Combined with the experimental results and numerical simulation of Euler type finite element method in the literature, the influences of material parameters on the penetration depth and length of the residual projectile at different impact velocities were analyzed. Numerical simulation was carried out based on the AUTODYN software. In the simulation process, tungsten alloy was described by the Grüneisen equation of state and Steinberg constitutive model, while concrete was described by the pressure-porosity equation of state and RHT dynamic damage constitutive model. The conclusions obtained are as follows. (1) If the toughness of the projectile material increases and the strength does not change, the characteristic parameters of the residual projectile, the penetration depth, and the velocity of the corresponding maximum penetration depth do not change significantly. (2) If the strength of the projectile material increases and the toughness is constant, the ability of the projectile to resist erosion can be enhanced, the residual length of the projectile increases, and the critical transition speed increases, thereby increasing the rigid penetration depth and total penetration depth. At the same time, the velocity corresponding to the maximum value of the projectile penetration depth increases.
In order to study the influence of projectile material parameters (mainly strength, toughness, etc.) on the penetration depth of hypervelocity penetrating concrete targets, experiments of 93W alloy column-shaped projectiles with different material properties penetrating concrete targets at
2024, 44(10): 105101.
doi: 10.11883/bzycj-2024-0068
Abstract:
In order to make a rapid assessment and design optimization of the protective performance of flexibly supported plate structure subjected to underwater explosion, a high-confidence simulation method is first established for the protective performance of flexibly supported plate structure subjected to underwater explosion. Then, underwater explosion tests were conducted on the flexibly supported plate structure to validate the computational accuracy of the developed high-confidence simulation method by comparing the deformation between the simulation results and the experimental results. The thickness of the blast-facing panel, the thickness of the flexible supports, and the thickness of the stiffened web are identified as the three key characteristic parameters that affect the protective performance of the flexibly supported plate. Utilizing optimized Latin-hypercube sampling method, 15 sample conditions are extracted from the sample space. The validated high-confidence simulation method is then used to generate protective performance data for these 15 sample conditions, which is subsequently employed to construct a proxy model for rapid assessment of the protective performance of the flexibly supported plates by using a radial basis function (RBF) neural network. The accuracy of the proxy model is assessed by using 5 randomly selected conditions, and the results show that the prediction error is within 7%, indicating a high level of prediction accuracy. The multi-island genetic algorithm (MIGA) is applied to the proxy model to perform multi-objective optimization and obtain a pareto set of solutions. The condition with the maximum specific ultimate energy absorption per unit mass is selected as the optimal structural parameters for the flexibly supported plate, achieving the goals on enhancing the ultimate protective performance and reducing the total structural mass. The rapid prediction and optimization method developed in this study provides significant technical support for the design and optimization of flexibly supported plate, and ensures both effective protection and weight savings.
In order to make a rapid assessment and design optimization of the protective performance of flexibly supported plate structure subjected to underwater explosion, a high-confidence simulation method is first established for the protective performance of flexibly supported plate structure subjected to underwater explosion. Then, underwater explosion tests were conducted on the flexibly supported plate structure to validate the computational accuracy of the developed high-confidence simulation method by comparing the deformation between the simulation results and the experimental results. The thickness of the blast-facing panel, the thickness of the flexible supports, and the thickness of the stiffened web are identified as the three key characteristic parameters that affect the protective performance of the flexibly supported plate. Utilizing optimized Latin-hypercube sampling method, 15 sample conditions are extracted from the sample space. The validated high-confidence simulation method is then used to generate protective performance data for these 15 sample conditions, which is subsequently employed to construct a proxy model for rapid assessment of the protective performance of the flexibly supported plates by using a radial basis function (RBF) neural network. The accuracy of the proxy model is assessed by using 5 randomly selected conditions, and the results show that the prediction error is within 7%, indicating a high level of prediction accuracy. The multi-island genetic algorithm (MIGA) is applied to the proxy model to perform multi-objective optimization and obtain a pareto set of solutions. The condition with the maximum specific ultimate energy absorption per unit mass is selected as the optimal structural parameters for the flexibly supported plate, achieving the goals on enhancing the ultimate protective performance and reducing the total structural mass. The rapid prediction and optimization method developed in this study provides significant technical support for the design and optimization of flexibly supported plate, and ensures both effective protection and weight savings.
