2024 Vol. 44, No. 2
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2024, 44(2): 021001.
doi: 10.11883/bzycj-2023-0214
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Abstract:
The remarkable energy absorption properties of the negative Poissonʼs ratio structure offer extensive prospects for applications in blast protection. However, the existing in-plane configurations of two-dimensional auxetic honeycomb cores always represent anisotropic behavior. To further enhance the blast resistance of sandwich panels, a three-dimensional sinusoidal curved-edge sandwich panel with a negative Poissonʼs ratio effect in both the X and Y directions for blast protection was proposed. The dynamic response and energy absorption characteristics under air blast load were studied by numerical simulation. Deformation modes and axial deflection distribution caused by plastic stretching and bending of the back face sheet were investigated in detail. The effects of stand-off distance (SOD), explosive mass, panel thickness, and key geometric parameters of the core layer on deformation and energy absorption were discussed. The results show that the dynamic response process of the sandwich panel can be divided into three stages: core compression, overall deformation, and free vibration. Moreover, it is found that there is no significant difference in the ability to resist deformation of the sandwich structure along the longitudinal (X) and transverse (Y) directions. As the TNT mass increases and the SOD decreases, the central displacement of the back face sheet of the sandwich panel increases, leading to a decrease in the energy absorption ratio of the core layer. Furthermore, utilizing a sandwich panel with a thin front panel and a thick back panel can increase the energy absorption proportion of the core layer. When increasing the thickness of the front and back panels by the same amount, the thickness of the front panel has a more significant effect on reducing the center displacement of the back panel. When the core thickness decreases from 0.6 mm to 0.2 mm, the back panel center displacement decreases by 49.0%, and the total energy absorption increases by 86.7%. As the core amplitude increases from 0.2mm to 1.0mm, the back panel center displacement decreases by 20.7%, with the total energy absorption remaining roughly constant. With an increase in core height from 10mm to 18mm, the back panel center displacement decreases by 88.3%, and the total energy absorption increases by 56.9%. Furthermore, a decrease in core aspect ratio from 0.56 to 0.2 results in a 39% reduction in back panel center displacement and a 47.4% increase in total energy absorption. The results of this study can guide the design of energy-absorbing protection for sandwich panels.
The remarkable energy absorption properties of the negative Poissonʼs ratio structure offer extensive prospects for applications in blast protection. However, the existing in-plane configurations of two-dimensional auxetic honeycomb cores always represent anisotropic behavior. To further enhance the blast resistance of sandwich panels, a three-dimensional sinusoidal curved-edge sandwich panel with a negative Poissonʼs ratio effect in both the X and Y directions for blast protection was proposed. The dynamic response and energy absorption characteristics under air blast load were studied by numerical simulation. Deformation modes and axial deflection distribution caused by plastic stretching and bending of the back face sheet were investigated in detail. The effects of stand-off distance (SOD), explosive mass, panel thickness, and key geometric parameters of the core layer on deformation and energy absorption were discussed. The results show that the dynamic response process of the sandwich panel can be divided into three stages: core compression, overall deformation, and free vibration. Moreover, it is found that there is no significant difference in the ability to resist deformation of the sandwich structure along the longitudinal (X) and transverse (Y) directions. As the TNT mass increases and the SOD decreases, the central displacement of the back face sheet of the sandwich panel increases, leading to a decrease in the energy absorption ratio of the core layer. Furthermore, utilizing a sandwich panel with a thin front panel and a thick back panel can increase the energy absorption proportion of the core layer. When increasing the thickness of the front and back panels by the same amount, the thickness of the front panel has a more significant effect on reducing the center displacement of the back panel. When the core thickness decreases from 0.6 mm to 0.2 mm, the back panel center displacement decreases by 49.0%, and the total energy absorption increases by 86.7%. As the core amplitude increases from 0.2mm to 1.0mm, the back panel center displacement decreases by 20.7%, with the total energy absorption remaining roughly constant. With an increase in core height from 10mm to 18mm, the back panel center displacement decreases by 88.3%, and the total energy absorption increases by 56.9%. Furthermore, a decrease in core aspect ratio from 0.56 to 0.2 results in a 39% reduction in back panel center displacement and a 47.4% increase in total energy absorption. The results of this study can guide the design of energy-absorbing protection for sandwich panels.
2024, 44(2): 021201.
doi: 10.11883/bzycj-2023-0183
Abstract:
The explosive implosion magnetic flux generator (EIMFG) could realize ultrahigh magnetic field by using explosive implosion to compress and cumulate inner magnetic flux into a smaller volume near axis. The EIMFG was designed by using magneto-hydrodynamics code of SSS-MHD and simulation shown that around 42% of initial magnetic flux would be finally compressed and cumulated into a volume of 7 mm in diameter near axis. The initial magnetic field system including specific solenoid, power source and large current switch was built up and had the ability of over 20 T of initial magnetic field producing in a cylinder space of 135 mm in diameter. A magnetic optical measurement system was also built up and suitable to dynamic detonation environment. Finally, a 20 kg TNT explosive sale EIMFG setup named CJ-150 was built up and axial maximum magnetic field up to 906 T was recorded using Faraday optical method. The original magneto-optical signal was clear with high quality, and uncertainty of maximum magnetic field data was 5.35%. The magnetic loading by Lorenz force was proved isentropic and uniform around from the measurement results of photonic Doppler velocimeter (PDV) probes which were set inside the sample tube. The CJ-150 setup is proved working stably and suitable to be used in physics experiment. Analysis show that CJ-150 could produce over 1000 T of ultrahigh magnetic field in over 10-1 cm3 volume and realize over 500 GPa of ultrahigh isentropic compression on large size sample.
The explosive implosion magnetic flux generator (EIMFG) could realize ultrahigh magnetic field by using explosive implosion to compress and cumulate inner magnetic flux into a smaller volume near axis. The EIMFG was designed by using magneto-hydrodynamics code of SSS-MHD and simulation shown that around 42% of initial magnetic flux would be finally compressed and cumulated into a volume of 7 mm in diameter near axis. The initial magnetic field system including specific solenoid, power source and large current switch was built up and had the ability of over 20 T of initial magnetic field producing in a cylinder space of 135 mm in diameter. A magnetic optical measurement system was also built up and suitable to dynamic detonation environment. Finally, a 20 kg TNT explosive sale EIMFG setup named CJ-150 was built up and axial maximum magnetic field up to 906 T was recorded using Faraday optical method. The original magneto-optical signal was clear with high quality, and uncertainty of maximum magnetic field data was 5.35%. The magnetic loading by Lorenz force was proved isentropic and uniform around from the measurement results of photonic Doppler velocimeter (PDV) probes which were set inside the sample tube. The CJ-150 setup is proved working stably and suitable to be used in physics experiment. Analysis show that CJ-150 could produce over 1000 T of ultrahigh magnetic field in over 10-1 cm3 volume and realize over 500 GPa of ultrahigh isentropic compression on large size sample.
2024, 44(2): 022301.
doi: 10.11883/bzycj-2023-0300
Abstract:
Based on the ignition experiment of HMX-based PBX explosive with long tube and strong constraint condition, numerical simulation is carried out by adopting the evolution growth model of explosive explosion reaction and multi-material arbitrary Lagrangian-Eulerian algorithm. The influence of ignition mode on the evolution law of explosive reaction is analyzed, and the characteristic image of explosive reaction evolution process under weak impact ignition condition is also obtained. Phenomenological model and numerical simulation method of PBX explosive ignition experiment under strong constraint conditions are constructed for two ignition modes of black powder and detonator, respectively. The characteristic images of explosive column reaction evolution process in steel pipe are obtained by numerical simulation, and the expansion process of cylinder shell is in good agreement with the experimental result. The study shows that there are great differences in the evolution process of explosive reaction under different ignition modes. If the detonator is used for ignition, the detonation reaction of PBX explosive will occur in a few microseconds; when the black powder is used for ignition while the long tube is strongly constrained, the PBX explosive will change from slow combustion to violent explosion in a few milliseconds. With the cracking and disintegration of the shell, the pressure in the tube will drop sharply, inhibiting the transition to detonation behavior, so the whole reaction evolution process under this ignition mode can be divided into four stages. The combustion propagation on the surface of explosive column near the tube wall takes precedence over the matrix reaction in the center of explosive column, which is an important feature of the evolution process of non-impact ignition reaction. The characteristic image and physical quantity curve obtained in this study reflect the evolution law of explosive reaction under the condition of weak impact ignition, which has important value for deepening the understanding of the hazard risk of explosive charge after accidental ignition.
Based on the ignition experiment of HMX-based PBX explosive with long tube and strong constraint condition, numerical simulation is carried out by adopting the evolution growth model of explosive explosion reaction and multi-material arbitrary Lagrangian-Eulerian algorithm. The influence of ignition mode on the evolution law of explosive reaction is analyzed, and the characteristic image of explosive reaction evolution process under weak impact ignition condition is also obtained. Phenomenological model and numerical simulation method of PBX explosive ignition experiment under strong constraint conditions are constructed for two ignition modes of black powder and detonator, respectively. The characteristic images of explosive column reaction evolution process in steel pipe are obtained by numerical simulation, and the expansion process of cylinder shell is in good agreement with the experimental result. The study shows that there are great differences in the evolution process of explosive reaction under different ignition modes. If the detonator is used for ignition, the detonation reaction of PBX explosive will occur in a few microseconds; when the black powder is used for ignition while the long tube is strongly constrained, the PBX explosive will change from slow combustion to violent explosion in a few milliseconds. With the cracking and disintegration of the shell, the pressure in the tube will drop sharply, inhibiting the transition to detonation behavior, so the whole reaction evolution process under this ignition mode can be divided into four stages. The combustion propagation on the surface of explosive column near the tube wall takes precedence over the matrix reaction in the center of explosive column, which is an important feature of the evolution process of non-impact ignition reaction. The characteristic image and physical quantity curve obtained in this study reflect the evolution law of explosive reaction under the condition of weak impact ignition, which has important value for deepening the understanding of the hazard risk of explosive charge after accidental ignition.
2024, 44(2): 023101.
doi: 10.11883/bzycj-2023-0235
Abstract:
As common structures in hydraulic engineering, the arch structures may suffer from explosion load during their operation life. In order to explore the dynamic response characteristics and failure features of reinforced concrete arches subjected to underwater explosions, two reinforced concrete arch specimens were fabricated and underwater explosion tests were carried out. The tests consisted of two groups: external explosion and internal explosion. 10 g emulsion explosives were used, and the minimum distance between the explosion source and the structure was 10 cm (the explosives were placed directly above or below the arch). The time history curves of water pressure and structural acceleration at typical sections of the arches during the explosion tests were recorded. Based on the Arbitrary Lagrange-Euler (ALE) algorithm, a multi-material dynamic coupling model, including air, water, explosive, and reinforced concrete arch was established. The initiation of explosive, the propagation of shock wave, the interaction between fluid and solid, and the dynamic response of the structure were considered in the numerical model. The reliability of the numerical model was verified by comparing the numerical results and the experimental results. With the calibrated numerical model, the difference of dynamic response of reinforced concrete arches under external explosion and internal explosion was further studied. The results show that more energy acts on the concrete arch, and the structural response is stronger when subjected to internal explosion. Large cracks occur at the vault and waist induced by external explosion. Compared with the external explosion, the number of cracks significantly increases under internal explosion, and cracks also appear at the spandrel. The ability of reinforced concrete arch to resist external explosive loads is significantly stronger than that of internal explosive loads although the explosive weight is the same. For concrete arches that are vulnerable to external explosions, high strength concrete or reinforced reinforcement can be appropriately used in the arch vault and waist. For concrete arches that may be subjected to internal explosions, protective nets can be set to make the explosion occur at a longer distance away from the structures, or high strength materials can be used to resist the overall deformation.
As common structures in hydraulic engineering, the arch structures may suffer from explosion load during their operation life. In order to explore the dynamic response characteristics and failure features of reinforced concrete arches subjected to underwater explosions, two reinforced concrete arch specimens were fabricated and underwater explosion tests were carried out. The tests consisted of two groups: external explosion and internal explosion. 10 g emulsion explosives were used, and the minimum distance between the explosion source and the structure was 10 cm (the explosives were placed directly above or below the arch). The time history curves of water pressure and structural acceleration at typical sections of the arches during the explosion tests were recorded. Based on the Arbitrary Lagrange-Euler (ALE) algorithm, a multi-material dynamic coupling model, including air, water, explosive, and reinforced concrete arch was established. The initiation of explosive, the propagation of shock wave, the interaction between fluid and solid, and the dynamic response of the structure were considered in the numerical model. The reliability of the numerical model was verified by comparing the numerical results and the experimental results. With the calibrated numerical model, the difference of dynamic response of reinforced concrete arches under external explosion and internal explosion was further studied. The results show that more energy acts on the concrete arch, and the structural response is stronger when subjected to internal explosion. Large cracks occur at the vault and waist induced by external explosion. Compared with the external explosion, the number of cracks significantly increases under internal explosion, and cracks also appear at the spandrel. The ability of reinforced concrete arch to resist external explosive loads is significantly stronger than that of internal explosive loads although the explosive weight is the same. For concrete arches that are vulnerable to external explosions, high strength concrete or reinforced reinforcement can be appropriately used in the arch vault and waist. For concrete arches that may be subjected to internal explosions, protective nets can be set to make the explosion occur at a longer distance away from the structures, or high strength materials can be used to resist the overall deformation.
2024, 44(2): 023102.
doi: 10.11883/bzycj-2022-0541
Abstract:
As the most widely used construction material, concrete is common in military protection and civil transportation infrastructures. During its services life, concrete may bear dynamic loads such as high-speed penetration, blast and impact of vehicle, ship, rockfall and so on. On the mesoscale, concrete is three-phase material composed of mortar, coarse aggregates and interface transition zone (ITZ). The concrete 3D mesoscale model was established to analyze the crack generation and development, damage evolution, dynamic strength and its influencing factors of concrete. Firstly, randomly distributed convex polyhedron aggregates of random shapes and sizes were modeled based on the conventional “take-and-place” method and Monte Carlo algorithm, and drop of aggregates under gravity were simulated in finite element software LS-DYNA to make aggregates more dense, improving aggregate volume fraction to 50%. After that, aggregate size was reduced by a trial value to control aggregate volume fraction conveniently. Then, aggregates and mortar were meshed with tetrahedral elements to display their actual physical shapes. Besides, ITZ was represented by interface cohesive contact which equals zero-thickness bonding elements to improve computational efficiency. Furthermore, SHPB simulations of different coarse aggregates sizes concrete were conducted and the accuracy of finite element model, parameter determination method and numerical simulation methods were proved by comparing test and simulated bar strain-time history, dynamic stress-strain curves and failure patterns of specimens. Finally, influences of the aggregate size (4−8, 10−14 and 22−26 mm), volume fraction (20%, 30% and 40%) and type (limestone, granite and basalt) on concrete dynamic compressive strength under the strain rate within 30−100 s−1 were analyzed. It shows that the dynamic compressive strength of concrete increases first and then decreases with the increase of aggregate size; the dynamic compressive strength of concrete increases with the increase of volume fraction; the dynamic compressive strength of concrete increases with the increase of aggregate strength.
As the most widely used construction material, concrete is common in military protection and civil transportation infrastructures. During its services life, concrete may bear dynamic loads such as high-speed penetration, blast and impact of vehicle, ship, rockfall and so on. On the mesoscale, concrete is three-phase material composed of mortar, coarse aggregates and interface transition zone (ITZ). The concrete 3D mesoscale model was established to analyze the crack generation and development, damage evolution, dynamic strength and its influencing factors of concrete. Firstly, randomly distributed convex polyhedron aggregates of random shapes and sizes were modeled based on the conventional “take-and-place” method and Monte Carlo algorithm, and drop of aggregates under gravity were simulated in finite element software LS-DYNA to make aggregates more dense, improving aggregate volume fraction to 50%. After that, aggregate size was reduced by a trial value to control aggregate volume fraction conveniently. Then, aggregates and mortar were meshed with tetrahedral elements to display their actual physical shapes. Besides, ITZ was represented by interface cohesive contact which equals zero-thickness bonding elements to improve computational efficiency. Furthermore, SHPB simulations of different coarse aggregates sizes concrete were conducted and the accuracy of finite element model, parameter determination method and numerical simulation methods were proved by comparing test and simulated bar strain-time history, dynamic stress-strain curves and failure patterns of specimens. Finally, influences of the aggregate size (4−8, 10−14 and 22−26 mm), volume fraction (20%, 30% and 40%) and type (limestone, granite and basalt) on concrete dynamic compressive strength under the strain rate within 30−100 s−1 were analyzed. It shows that the dynamic compressive strength of concrete increases first and then decreases with the increase of aggregate size; the dynamic compressive strength of concrete increases with the increase of volume fraction; the dynamic compressive strength of concrete increases with the increase of aggregate strength.
2024, 44(2): 023103.
doi: 10.11883/bzycj-2023-0176
Abstract:
Ultra-high molecular weight polyethylene (UHMWPE) fibers are widely used in explosive fragment protection due to their high modulus, high strength, and low density. To study the effect of UHMWPE backplate thickness on the penetration resistance effect of aluminum composite panel, the digital image correlation method (DIC) and computed tomography (CT) were used to obtain the dynamic response and local failure of UHMWPE. A finite element model of a tungsten ball penetrating an Al/PE composite plate with different speeds (500, 1000, and 1500 m/s) was established, and the simulated results were found to be in good agreement with the experimental results. The influence of PE backplate thickness on the energy absorption performance and strain of the composite target plate was mainly studied, and the thickness of the backplate was 1.6-20 mm. The results demonstrate that the aluminum plate undergoes adiabatic shear failure under the impact, and the fiber layers are laid orthogonally to produce fiber bulges and bifurcated strain bands under tension. The fiber bulge and cross-shaped strain band bifurcation phenomenon occur when the fragments penetrate the orthogonally laid fibers. With the increase of the PE plate thickness, the main failure of the fiber layers changes from shear failure to tensile failure, and the strain band of the fiber layers changes from cross shape to X shape. Increasing the thickness of the PE plate hinders the movement of the plug body of the aluminum block, thereby increasing the time and kinetic energy consumption of the fragment penetrating the aluminum plate. When the impact velocity is 500, 1000 and 1500 m/s, the optimal areal density absorption energy thickness respectively is 6.4, 12, and 16 mm, and the surface density energy absorption respectively is 14.55, 49.51 and 98.07 J·(kg·m2). The influence of PE composite plate thickness on energy absorption performance first rises rapidly to the threshold and then slowly decreases, this result shows that increasing the PE plate thickness is limited in improving its energy absorption performance after reaching a certain thickness.
Ultra-high molecular weight polyethylene (UHMWPE) fibers are widely used in explosive fragment protection due to their high modulus, high strength, and low density. To study the effect of UHMWPE backplate thickness on the penetration resistance effect of aluminum composite panel, the digital image correlation method (DIC) and computed tomography (CT) were used to obtain the dynamic response and local failure of UHMWPE. A finite element model of a tungsten ball penetrating an Al/PE composite plate with different speeds (500, 1000, and 1500 m/s) was established, and the simulated results were found to be in good agreement with the experimental results. The influence of PE backplate thickness on the energy absorption performance and strain of the composite target plate was mainly studied, and the thickness of the backplate was 1.6-20 mm. The results demonstrate that the aluminum plate undergoes adiabatic shear failure under the impact, and the fiber layers are laid orthogonally to produce fiber bulges and bifurcated strain bands under tension. The fiber bulge and cross-shaped strain band bifurcation phenomenon occur when the fragments penetrate the orthogonally laid fibers. With the increase of the PE plate thickness, the main failure of the fiber layers changes from shear failure to tensile failure, and the strain band of the fiber layers changes from cross shape to X shape. Increasing the thickness of the PE plate hinders the movement of the plug body of the aluminum block, thereby increasing the time and kinetic energy consumption of the fragment penetrating the aluminum plate. When the impact velocity is 500, 1000 and 1500 m/s, the optimal areal density absorption energy thickness respectively is 6.4, 12, and 16 mm, and the surface density energy absorption respectively is 14.55, 49.51 and 98.07 J·(kg·m2). The influence of PE composite plate thickness on energy absorption performance first rises rapidly to the threshold and then slowly decreases, this result shows that increasing the PE plate thickness is limited in improving its energy absorption performance after reaching a certain thickness.
2024, 44(2): 023104.
doi: 10.11883/bzycj-2023-0182
Abstract:
The critical condition of tensile tearing failure of stiffened plate under impact load was studied. Firstly, the unidirectional stiffened plate with fixed support under uniform impact load was simplified into beam structure model attached with band plate. Based on the theoretical solution of the impact deformation of the fixed beam, the theoretical solution of the maximum deformation of the stiffened plate was given. At the same time, the applicable condition for calculating the large deformation of the unidirectional stiffened plate by using the “beam theory” model was given. Then, the motion mode of the fixed beam under strong impact load was divided into four stages. Based on the composite motion model, the relation between the tensile strain at the end of fixed beam and the maximum deformation of beam was corrected. Finally, taking equivalent strain equal to failure strain as the tensile tear condition, the critical condition of tensile tear of stiffened plate under impact load was established. In this paper, three unidirectional stiffened plates of T profile with different stiffness were selected, and the maximum deformation and critical tensile tearing load of the stiffened plates were analyzed by commercial finite element software LS-DYNA. The numerical simulation results show that the theoretical solution of maximum deformation of unidirectional stiffened plate and the critical condition of tensile tear failure based on the “beam theory” are applicable, and The error of theoretical and numerical simulation is less than 15%. Therefore, the theory in this paper can be applied to practical engineering prediction and has certain guiding significance.
The critical condition of tensile tearing failure of stiffened plate under impact load was studied. Firstly, the unidirectional stiffened plate with fixed support under uniform impact load was simplified into beam structure model attached with band plate. Based on the theoretical solution of the impact deformation of the fixed beam, the theoretical solution of the maximum deformation of the stiffened plate was given. At the same time, the applicable condition for calculating the large deformation of the unidirectional stiffened plate by using the “beam theory” model was given. Then, the motion mode of the fixed beam under strong impact load was divided into four stages. Based on the composite motion model, the relation between the tensile strain at the end of fixed beam and the maximum deformation of beam was corrected. Finally, taking equivalent strain equal to failure strain as the tensile tear condition, the critical condition of tensile tear of stiffened plate under impact load was established. In this paper, three unidirectional stiffened plates of T profile with different stiffness were selected, and the maximum deformation and critical tensile tearing load of the stiffened plates were analyzed by commercial finite element software LS-DYNA. The numerical simulation results show that the theoretical solution of maximum deformation of unidirectional stiffened plate and the critical condition of tensile tear failure based on the “beam theory” are applicable, and The error of theoretical and numerical simulation is less than 15%. Therefore, the theory in this paper can be applied to practical engineering prediction and has certain guiding significance.
2024, 44(2): 023201.
doi: 10.11883/bzycj-2023-0184
Abstract:
The real gas flows of a reflected high-enthalpy shock tunnel are investigated by quasi-one-dimensional numerical simulation based on cubic equations of state, focusing on the influence of high-pressure real gas effect on the spatio-temporal structure of the full-field flow and the flow parameters in the stagnation zone right before the nozzle throat. In the numerical simulations, the thermochemical non-equilibrium due to high temperature caused by shock waves is considered. By embedding cubic equations of state into gas dynamics relations, theoretical analysis is also performed to find out the mechanism of high-pressure effect on the shock tube flow. It is shown that for shock tunnel flows driven by cold and high-pressure gas, the use of a real gas equation of state that takes into account molecular volume and intermolecular forces can more accurately describe the thermodynamic states of gas and the flow conditions in shock tunnels. The high-pressure real gas effect mainly occurs in the cold driving gas, which increases the local sound speed and hence increases the propagation speed of the incident and reflected rarefaction waves; on the other hand, the high-pressure real gas effect plays a weak role in the driven section where the high-temperature gas effect is significant, while it has little effect on the intensity of the shock wave generated by the shock tube as well as the flow state behind the shock. The increase of rarefaction wave speed changes the intersecting time and space of the wave system, which may alter the order of arrival of the reflected rarefaction wave and the contact surface in the stagnation zone. Under this circumstance, the early arrival of rarefaction wave shortens the effective test time of the shock tunnel. For the tested shock tunnel configuration, the high-pressure real gas effect reduces the effective test time by about 38% under the condition of 150 MPa hydrogen driving 110 kPa nitrogen. Both lengthening of the driver section and using high-temperature driver gas can effectively dissolve the influence of the aforementioned high-pressure effect.
The real gas flows of a reflected high-enthalpy shock tunnel are investigated by quasi-one-dimensional numerical simulation based on cubic equations of state, focusing on the influence of high-pressure real gas effect on the spatio-temporal structure of the full-field flow and the flow parameters in the stagnation zone right before the nozzle throat. In the numerical simulations, the thermochemical non-equilibrium due to high temperature caused by shock waves is considered. By embedding cubic equations of state into gas dynamics relations, theoretical analysis is also performed to find out the mechanism of high-pressure effect on the shock tube flow. It is shown that for shock tunnel flows driven by cold and high-pressure gas, the use of a real gas equation of state that takes into account molecular volume and intermolecular forces can more accurately describe the thermodynamic states of gas and the flow conditions in shock tunnels. The high-pressure real gas effect mainly occurs in the cold driving gas, which increases the local sound speed and hence increases the propagation speed of the incident and reflected rarefaction waves; on the other hand, the high-pressure real gas effect plays a weak role in the driven section where the high-temperature gas effect is significant, while it has little effect on the intensity of the shock wave generated by the shock tube as well as the flow state behind the shock. The increase of rarefaction wave speed changes the intersecting time and space of the wave system, which may alter the order of arrival of the reflected rarefaction wave and the contact surface in the stagnation zone. Under this circumstance, the early arrival of rarefaction wave shortens the effective test time of the shock tunnel. For the tested shock tunnel configuration, the high-pressure real gas effect reduces the effective test time by about 38% under the condition of 150 MPa hydrogen driving 110 kPa nitrogen. Both lengthening of the driver section and using high-temperature driver gas can effectively dissolve the influence of the aforementioned high-pressure effect.
2024, 44(2): 023202.
doi: 10.11883/bzycj-2023-0262
Abstract:
The purpose of this research work is to look into the time-space evolution of plasma pressure for femtosecond pulse laser shock peening (fs-LSP). In this study, propose a model to understand plasma pressure over time-space process in fs-LSP based on the first principle, improved two temperature equations, and plasma hydrodynamic equations. Firstly analyze the plasma plume front location with respect to time by solving the plasma hydrodynamic equations. The simulated results by the electron DOS (density of state) femtosecond pulse laser shock peening model are in better agreement with the experiment results than the QEOS (quotidian equation of state) femtosecond pulse laser shock peening model. The DOS femtosecond pulse laser shock peening model was shown to be effective and superior. Then use the DOS model to calculate how the electron heat capacity and electron-phonon coefficient with respect to electron temperature. Electron heat capacity calculated by the QEOS model is larger than calculated by the electron DOS model, whereas the electron-phonon coefficient is the reverse. Moreover, the electron-phonon coefficient calculated by the QEOS model shows linear variation with respect to the electron temperature, which is the reverse of that calculated by the electron DOS model. Therefore, the electron DOS effect should be considered in two-temperature equations. Next see a graph of electron and lattice temperature with respect to time using the modified two-temperature equations to calculate. Increasing laser energy, decreasing pulse width, and considering the electron DOS effect will increase the electron’s peak temperature, and equilibrium temperature of electron and lattice systems, and reduce the electron-phonon relaxation time. Finally, we utilize the results of the two temperature equations as the initial condition to substitute into the plasma hydrodynamic equations to compute the plasma pressure. plasma peak pressure will rise as laser energy is increased, the pulse width is decreased, and the electron DOS effect is taken into account.
The purpose of this research work is to look into the time-space evolution of plasma pressure for femtosecond pulse laser shock peening (fs-LSP). In this study, propose a model to understand plasma pressure over time-space process in fs-LSP based on the first principle, improved two temperature equations, and plasma hydrodynamic equations. Firstly analyze the plasma plume front location with respect to time by solving the plasma hydrodynamic equations. The simulated results by the electron DOS (density of state) femtosecond pulse laser shock peening model are in better agreement with the experiment results than the QEOS (quotidian equation of state) femtosecond pulse laser shock peening model. The DOS femtosecond pulse laser shock peening model was shown to be effective and superior. Then use the DOS model to calculate how the electron heat capacity and electron-phonon coefficient with respect to electron temperature. Electron heat capacity calculated by the QEOS model is larger than calculated by the electron DOS model, whereas the electron-phonon coefficient is the reverse. Moreover, the electron-phonon coefficient calculated by the QEOS model shows linear variation with respect to the electron temperature, which is the reverse of that calculated by the electron DOS model. Therefore, the electron DOS effect should be considered in two-temperature equations. Next see a graph of electron and lattice temperature with respect to time using the modified two-temperature equations to calculate. Increasing laser energy, decreasing pulse width, and considering the electron DOS effect will increase the electron’s peak temperature, and equilibrium temperature of electron and lattice systems, and reduce the electron-phonon relaxation time. Finally, we utilize the results of the two temperature equations as the initial condition to substitute into the plasma hydrodynamic equations to compute the plasma pressure. plasma peak pressure will rise as laser energy is increased, the pulse width is decreased, and the electron DOS effect is taken into account.
2024, 44(2): 023301.
doi: 10.11883/bzycj-2023-0071
Abstract:
A series of high-speed ballistic impact tests were conducted on a two-stage light gas gun to investigate the perforation behaviors of Inconel 718 (IN718) superalloy plates. The IN718 targets were prepared with 2 mm thickness, and the 5 mm diameter SS304 spheres were used as projectiles. The impact velocity ranged from 548.2 m/s to 1 067.0 m/s. The shadow graphs of the impact process were captured by using a high-speed camera at a frame rate of 160 000 frames per second. The projectile residual velocities after perforation were then obtained from snapshots and analyzed. The Rechi-Ipson model was employed for the investigated projectile-target combination by fitting the projectile initial velocity-residual velocity relationship, and the ballistic limit velocity 561.0 m/s was then verified. The maximum deformation deflection of the ballistic impact-recovered plates was measured using a height gauge. The optical morphology of the postmortem target was captured, the deformation and failure modes of the target material were observed, while the bullet hole diameters were measured. The experimental results reveal that within the investigated impact velocity range, as the impact velocity increases, the failure mode of the target material changes from tension-dominated failure to tension/shear-dominated failure. The perforation failure mode of the plates is closely associated with the impact velocity. The energy absorption efficiency of the target plates decreases with the increase of projectile’s initial kinetic energy, and it approaches a constant of 0.7. The deformation of the plates decreases with the increase of impact velocity, with the maximum deformation deflection occurring near the ballistic limit. The bullet hole diameters on the front and rear side both increase with the increase of impact velocity, and the bullet hole diameter on the rear side is greater than that on the front side. It is evident that investigating the deformation, failure modes, and ballistic properties of IN718 superalloy under high-speed ballistic impact is essential for its industrial applications.
A series of high-speed ballistic impact tests were conducted on a two-stage light gas gun to investigate the perforation behaviors of Inconel 718 (IN718) superalloy plates. The IN718 targets were prepared with 2 mm thickness, and the 5 mm diameter SS304 spheres were used as projectiles. The impact velocity ranged from 548.2 m/s to 1 067.0 m/s. The shadow graphs of the impact process were captured by using a high-speed camera at a frame rate of 160 000 frames per second. The projectile residual velocities after perforation were then obtained from snapshots and analyzed. The Rechi-Ipson model was employed for the investigated projectile-target combination by fitting the projectile initial velocity-residual velocity relationship, and the ballistic limit velocity 561.0 m/s was then verified. The maximum deformation deflection of the ballistic impact-recovered plates was measured using a height gauge. The optical morphology of the postmortem target was captured, the deformation and failure modes of the target material were observed, while the bullet hole diameters were measured. The experimental results reveal that within the investigated impact velocity range, as the impact velocity increases, the failure mode of the target material changes from tension-dominated failure to tension/shear-dominated failure. The perforation failure mode of the plates is closely associated with the impact velocity. The energy absorption efficiency of the target plates decreases with the increase of projectile’s initial kinetic energy, and it approaches a constant of 0.7. The deformation of the plates decreases with the increase of impact velocity, with the maximum deformation deflection occurring near the ballistic limit. The bullet hole diameters on the front and rear side both increase with the increase of impact velocity, and the bullet hole diameter on the rear side is greater than that on the front side. It is evident that investigating the deformation, failure modes, and ballistic properties of IN718 superalloy under high-speed ballistic impact is essential for its industrial applications.
2024, 44(2): 023302.
doi: 10.11883/bzycj-2022-0282
Abstract:
Aiming to evaluate the penetration resistance of the ultra high performance concrete (UHPC) target, both penetration tests and numerical simulations were carried out on UHPC targets. Firstly, the\begin{document}$\varnothing $\end{document} ![]()
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Aiming to evaluate the penetration resistance of the ultra high performance concrete (UHPC) target, both penetration tests and numerical simulations were carried out on UHPC targets. Firstly, the
2024, 44(2): 025101.
doi: 10.11883/bzycj-2023-0166
Abstract:
An appropriate material model can accurately predict the mechanical behavior and damage mode of foam concrete subjected to blast loadings, and it has great significance on the design of composite protective structure. The purpose of this paper is to apply the new dynamic plastic-damage model for foam concrete presented by author to protective structures. Firstly, the new foam concrete model was briefly introduced. The model includes the definition of plasticity by introducing a yield function, flow rule and hardening law, the introduction of strain-rate effect and the definition of damage using plastic strain or related quantities. Subsequently, in order to validate the new model, the blast tests on the composite protective structure sandwiched by foam concrete with different strength were conducted and the stress waves at specific location and damage in foam concrete were recorded. Furthermore, the numerical results predicted by the new foam concrete model were compared to those predicted by the Soil and Foam model in the LS-DYNA. Finally, blast response of composite protective structure sandwiched by gradient foam concrete was numerically investigated based on the validated numerical model. The influences of arrangement and layers in gradient foam concrete layer on the anti-blast capability of composite protective structure were discussed by various working conditions. The results indicate that the numerical predictions excellently agreed with corresponding test data, demonstrating the accuracy of material model for foam concrete under blast loadings. Compared with the Soil and Foam model, the new model predicted better in terms of amplitude and duration of load on the structural layer, as well as the damage and failure in foam concrete layer. The gradient foam concrete numerical result showed that the arrangement and layers of foam concrete with different strength had an effect on the stress duration acting on the structure layer and the damage of the distribution layer. The new dynamic plastic-damage model for foam concrete has a broad application prospect in the research of protective structures
An appropriate material model can accurately predict the mechanical behavior and damage mode of foam concrete subjected to blast loadings, and it has great significance on the design of composite protective structure. The purpose of this paper is to apply the new dynamic plastic-damage model for foam concrete presented by author to protective structures. Firstly, the new foam concrete model was briefly introduced. The model includes the definition of plasticity by introducing a yield function, flow rule and hardening law, the introduction of strain-rate effect and the definition of damage using plastic strain or related quantities. Subsequently, in order to validate the new model, the blast tests on the composite protective structure sandwiched by foam concrete with different strength were conducted and the stress waves at specific location and damage in foam concrete were recorded. Furthermore, the numerical results predicted by the new foam concrete model were compared to those predicted by the Soil and Foam model in the LS-DYNA. Finally, blast response of composite protective structure sandwiched by gradient foam concrete was numerically investigated based on the validated numerical model. The influences of arrangement and layers in gradient foam concrete layer on the anti-blast capability of composite protective structure were discussed by various working conditions. The results indicate that the numerical predictions excellently agreed with corresponding test data, demonstrating the accuracy of material model for foam concrete under blast loadings. Compared with the Soil and Foam model, the new model predicted better in terms of amplitude and duration of load on the structural layer, as well as the damage and failure in foam concrete layer. The gradient foam concrete numerical result showed that the arrangement and layers of foam concrete with different strength had an effect on the stress duration acting on the structure layer and the damage of the distribution layer. The new dynamic plastic-damage model for foam concrete has a broad application prospect in the research of protective structures
2024, 44(2): 025102.
doi: 10.11883/bzycj-2023-0126
Abstract:
The reported study focuses on the investigation of the impact response of a titanium alloy directional detonation container when it is subjected to explosives at different positions. Through experimental and numerical simulation studies, the explosion resistance of the container and the flight angle of the impact plug are investigated when 100 g of TNT is placed in different positions. In order to restrict the motion of the container, the axial force on the container is analyzed. The results show that the container undergoes elastic deformation when the explosive is located on the axis. When it is in close contact with the middle of the inner wall, the outer wall of the container bulges and cracks. When it is in close contact with the near end of the inner wall, the outer wall of the container protrudes. Under the action of 100 g of TNT, the average velocity of the impact plug outlet is 124.45 m/s, and the maximum deviation angle is 2.3°. The explosive position has little influence on the velocity of the plug outlet. When the explosive is located at the front and rear ends of the axis, the axial force increases by 173% and 116%, respectively, compared to that when the explosive is located at the center of the axis. The study can provide reference to the design of directional detonation container and connection structure of civil aircraft.
The reported study focuses on the investigation of the impact response of a titanium alloy directional detonation container when it is subjected to explosives at different positions. Through experimental and numerical simulation studies, the explosion resistance of the container and the flight angle of the impact plug are investigated when 100 g of TNT is placed in different positions. In order to restrict the motion of the container, the axial force on the container is analyzed. The results show that the container undergoes elastic deformation when the explosive is located on the axis. When it is in close contact with the middle of the inner wall, the outer wall of the container bulges and cracks. When it is in close contact with the near end of the inner wall, the outer wall of the container protrudes. Under the action of 100 g of TNT, the average velocity of the impact plug outlet is 124.45 m/s, and the maximum deviation angle is 2.3°. The explosive position has little influence on the velocity of the plug outlet. When the explosive is located at the front and rear ends of the axis, the axial force increases by 173% and 116%, respectively, compared to that when the explosive is located at the center of the axis. The study can provide reference to the design of directional detonation container and connection structure of civil aircraft.
2024, 44(2): 025201.
doi: 10.11883/bzycj-2023-0217
Abstract:
In tunnel blasting and excavation engineering, blasting vibration is the main harmful effect affecting safety and stability. In order to investigate the generation mechanism and propagation patterns of seismic waves resulting from blasting in tunnel contexts, a theoretical model based on plane strain conditions is developed to depict the tunnel surface vibration caused by blasting. Then, a solution in integral form is derived to describe the surface vibration field generated from tunnel blasting. Utilizing the Longnan tunnel blasting project as a contextual backdrop, a finite element numerical model is established to recreate the conditions. This allows for the validation of both the numerical simulations and theoretical solutions through on-site tests. To elucidate the propagation characteristics of distinct types of seismic waves resulting from blasting, a method adopting a high-resolution Radon transform approach is devised to separate the tunnel blasting seismic wave field. By combining theoretical analysis with numerical simulation, the propagation characteristics of P-waves, S-waves, and R-waves are ascertained. Further, by synthesizing theoretical results and wave field separation results, the seismic wave action partition of tunnel blasting is proposed. The results show that tunnel blasting excites P-waves and S-waves, while R-waves surge swiftly upon encountering the free surface. The triad of wave categories displays exponential attenuation tendencies, with S-waves demonstrating a swifter decay rate than P-waves, and P-waves outpacing R-waves in this regard. In terms of directional dominance, the main component in the vertical direction changes from S-wave to R-wave, and the main component in the horizontal direction changes from S-wave to P-wave, and then P-wave changes to R-wave. A detailed spatial analysis further elucidates this scenario. Under the working conditions of grade Ⅳ surrounding rock, the seismic wave action zone of tunnel blasting is as follows: the area of 0–6.44 m away from the tunnel axis to the tunnel face is regarded as the near area of blasting, where the dominant wave type is horizontal S-wave; the area of 6.44–21.23 m is regarded as the middle area of blasting, where the dominant wave type is horizontal P-wave; and the area beyond 21.23 m is regarded as blasting far zone, where the dominant wave type is vertical R-wave. In addition, a linear relationship exists between the boundary point of the blasting zone and the maximum amount of charge in a single section, and the position of the blasting zone in the tunnel can be obtained through the amount of blasting charge, which can be used for the analysis of the safety and stability of the tunnel.
In tunnel blasting and excavation engineering, blasting vibration is the main harmful effect affecting safety and stability. In order to investigate the generation mechanism and propagation patterns of seismic waves resulting from blasting in tunnel contexts, a theoretical model based on plane strain conditions is developed to depict the tunnel surface vibration caused by blasting. Then, a solution in integral form is derived to describe the surface vibration field generated from tunnel blasting. Utilizing the Longnan tunnel blasting project as a contextual backdrop, a finite element numerical model is established to recreate the conditions. This allows for the validation of both the numerical simulations and theoretical solutions through on-site tests. To elucidate the propagation characteristics of distinct types of seismic waves resulting from blasting, a method adopting a high-resolution Radon transform approach is devised to separate the tunnel blasting seismic wave field. By combining theoretical analysis with numerical simulation, the propagation characteristics of P-waves, S-waves, and R-waves are ascertained. Further, by synthesizing theoretical results and wave field separation results, the seismic wave action partition of tunnel blasting is proposed. The results show that tunnel blasting excites P-waves and S-waves, while R-waves surge swiftly upon encountering the free surface. The triad of wave categories displays exponential attenuation tendencies, with S-waves demonstrating a swifter decay rate than P-waves, and P-waves outpacing R-waves in this regard. In terms of directional dominance, the main component in the vertical direction changes from S-wave to R-wave, and the main component in the horizontal direction changes from S-wave to P-wave, and then P-wave changes to R-wave. A detailed spatial analysis further elucidates this scenario. Under the working conditions of grade Ⅳ surrounding rock, the seismic wave action zone of tunnel blasting is as follows: the area of 0–6.44 m away from the tunnel axis to the tunnel face is regarded as the near area of blasting, where the dominant wave type is horizontal S-wave; the area of 6.44–21.23 m is regarded as the middle area of blasting, where the dominant wave type is horizontal P-wave; and the area beyond 21.23 m is regarded as blasting far zone, where the dominant wave type is vertical R-wave. In addition, a linear relationship exists between the boundary point of the blasting zone and the maximum amount of charge in a single section, and the position of the blasting zone in the tunnel can be obtained through the amount of blasting charge, which can be used for the analysis of the safety and stability of the tunnel.
