2023 Vol. 43, No. 7
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2023, 43(7): 071101.
doi: 10.11883/bzycj-2022-0251
Abstract:
Energetic materials are a novel class of substances that can produce chemical reactions, releasing significant amounts of energy when exposed to high temperatures and pressures. Metallic energetic materials have become a key component in modern weaponry and equipment due to their exceptional properties, including high density, strength, and stability. These materials possess significant potential for use in fragmentation warheads and other military applications. Among various characters, the mechanical properties of materials directly affect the penetration ability of the weapons equipment on the target and determine the final damage power of the target, which has always been one of the key parameters in the application of the weapons and equipment. In order to achieve high armor-piercing ability and high energy release characteristics of metallic energetic materials, extensive research has been conducted by scholars on their mechanical characteristics. In this paper, the current research status on the mechanical behavior of metallic energetic materials is reviewed, including a brief introduction of the preparation technology and mechanical property testing system of metallic energetic materials, as well as a detailed review of research progress in their mechanical properties, microscopic analysis, and theoretical studies. It is concluded that there have been significant achievements in studying the mechanical properties of these materials, but there remains a lack of investigation into their behavior under complex environmental conditions and other key processes. At the same time, there is a lack of research on the influence of material microscopic properties on their mechanical properties and the correlation mechanism between microscopic and macroscopic behaviors. Furthermore, an accurate mechanical theoretical model that can effectively capture the complex conditions of materials such as temperature, loading rate, and stress has yet to be established. Therefore, the development of metallic energetic materials with superior performance, investigation into the mechanical properties of metallic energetic fragments under complex conditions, exploration of the correlation mechanism between micro and macro behavior, and establishment and refinement of material constitutive models will be the key issue for advancing the engineering application of metallic energetic materials.
Energetic materials are a novel class of substances that can produce chemical reactions, releasing significant amounts of energy when exposed to high temperatures and pressures. Metallic energetic materials have become a key component in modern weaponry and equipment due to their exceptional properties, including high density, strength, and stability. These materials possess significant potential for use in fragmentation warheads and other military applications. Among various characters, the mechanical properties of materials directly affect the penetration ability of the weapons equipment on the target and determine the final damage power of the target, which has always been one of the key parameters in the application of the weapons and equipment. In order to achieve high armor-piercing ability and high energy release characteristics of metallic energetic materials, extensive research has been conducted by scholars on their mechanical characteristics. In this paper, the current research status on the mechanical behavior of metallic energetic materials is reviewed, including a brief introduction of the preparation technology and mechanical property testing system of metallic energetic materials, as well as a detailed review of research progress in their mechanical properties, microscopic analysis, and theoretical studies. It is concluded that there have been significant achievements in studying the mechanical properties of these materials, but there remains a lack of investigation into their behavior under complex environmental conditions and other key processes. At the same time, there is a lack of research on the influence of material microscopic properties on their mechanical properties and the correlation mechanism between microscopic and macroscopic behaviors. Furthermore, an accurate mechanical theoretical model that can effectively capture the complex conditions of materials such as temperature, loading rate, and stress has yet to be established. Therefore, the development of metallic energetic materials with superior performance, investigation into the mechanical properties of metallic energetic fragments under complex conditions, exploration of the correlation mechanism between micro and macro behavior, and establishment and refinement of material constitutive models will be the key issue for advancing the engineering application of metallic energetic materials.
2023, 43(7): 072201.
doi: 10.11883/bzycj-2022-0468
Abstract:
In order to study the dynamic response and failure characteristics of the concrete girder with single box and three chambers under near-field explosion, the explosion test and numerical simulation of a scaled specimen were carried out. The girder specimen was designed and manufactured by the scale of 1∶3 according to the prototype bridge girder. The bottom of the specimen was supported by six brick supports. The TNT grain was located at 0.4 m above the top plate center of the middle chamber with an equivalent of 3 kg and a proportional distance of 0.77 m/kg1/3. The reflected overpressure, reinforcement strain, vertical displacement and acceleration of bottom plate and the shape of breach were measured and analyzed. The effectiveness of the explosion load in the test was verified by comparing the measured reflection overpressure with the calculated value by the CONWEP empirical formula. The LS-DYNA software was used to simulate the explosion response of the box girder. The SOLIDWORKS software and HYPERMESH software were used to establish the finite element model of the specimen. The Solid 164 element was used to simulate the concrete, and Beam 188 element was used to simulate the steel rebar. The LOAD BLAST ENHANCED (LBE) method was used to apply explosive loads. The *MAT_CONCRETE_DAMAGE_REL3 material model and *MAT_PLASTIC_KINEMATIC model were used to simulate the concrete and rebar, respectively, to consider the effects caused by high strain and large deformation. The keyword *MAT_ADD_EROSION was used to define the failure of concrete. The reliability of numerical simulation method was verified with the test data. Finally, the effects of TNT equivalent, detonation location, concrete strength, and reinforcement ratio on the explosion resistance of the box girder were analyzed. The results show that when a TNT grain of 3 kg is detonated at 0.4 m above the center of the middle chamber of the box girder, an elliptical penetration breach is formed in the center of top plate of the middle chamber, with the length values along the transverse and longitudinal bridge directions being 41.50 and 45.50 cm, respectively. The concrete on the bottom surface of the top plate of the middle chamber peels off in a large area, presenting a trumpet-shaped punching failure feature. The extra-wide cross-section of multi-chamber box girder makes the explosive responses unevenly distributing along the transverse bridge direction. The peak values of vertical displacement and rebar strain of the bottom plate of the girder increase with the increase of the charge. Using the least square method, the corresponding fitting curve expressions are obtained. Under the working conditions of different detonation positions, the vertical displacement of the bottom plate center of the middle chamber is greater than those of the chamber centers on both sides. The results can provide a basis for the anti-explosive evaluation and protection of similar extra-wide concrete box girder.
In order to study the dynamic response and failure characteristics of the concrete girder with single box and three chambers under near-field explosion, the explosion test and numerical simulation of a scaled specimen were carried out. The girder specimen was designed and manufactured by the scale of 1∶3 according to the prototype bridge girder. The bottom of the specimen was supported by six brick supports. The TNT grain was located at 0.4 m above the top plate center of the middle chamber with an equivalent of 3 kg and a proportional distance of 0.77 m/kg1/3. The reflected overpressure, reinforcement strain, vertical displacement and acceleration of bottom plate and the shape of breach were measured and analyzed. The effectiveness of the explosion load in the test was verified by comparing the measured reflection overpressure with the calculated value by the CONWEP empirical formula. The LS-DYNA software was used to simulate the explosion response of the box girder. The SOLIDWORKS software and HYPERMESH software were used to establish the finite element model of the specimen. The Solid 164 element was used to simulate the concrete, and Beam 188 element was used to simulate the steel rebar. The LOAD BLAST ENHANCED (LBE) method was used to apply explosive loads. The *MAT_CONCRETE_DAMAGE_REL3 material model and *MAT_PLASTIC_KINEMATIC model were used to simulate the concrete and rebar, respectively, to consider the effects caused by high strain and large deformation. The keyword *MAT_ADD_EROSION was used to define the failure of concrete. The reliability of numerical simulation method was verified with the test data. Finally, the effects of TNT equivalent, detonation location, concrete strength, and reinforcement ratio on the explosion resistance of the box girder were analyzed. The results show that when a TNT grain of 3 kg is detonated at 0.4 m above the center of the middle chamber of the box girder, an elliptical penetration breach is formed in the center of top plate of the middle chamber, with the length values along the transverse and longitudinal bridge directions being 41.50 and 45.50 cm, respectively. The concrete on the bottom surface of the top plate of the middle chamber peels off in a large area, presenting a trumpet-shaped punching failure feature. The extra-wide cross-section of multi-chamber box girder makes the explosive responses unevenly distributing along the transverse bridge direction. The peak values of vertical displacement and rebar strain of the bottom plate of the girder increase with the increase of the charge. Using the least square method, the corresponding fitting curve expressions are obtained. Under the working conditions of different detonation positions, the vertical displacement of the bottom plate center of the middle chamber is greater than those of the chamber centers on both sides. The results can provide a basis for the anti-explosive evaluation and protection of similar extra-wide concrete box girder.
2023, 43(7): 072301.
doi: 10.11883/bzycj-2022-0555
Abstract:
In order to explore the cook-off response characteristics of the JH-14C booster explosive with a shell under different external temperatures, a set of experimental devices was designed for measuring the cook-off response temperatures at multiple points of the JH-14C booster explosive and for monitoring the deformation of the shell. The explosive temperatures were measured from its edge to its center. The strain-time curves of the shell were recorded by a dynamic strain indicator and a high-temperature strain gauge. The cook-off experiments with the heating rates of 1.0 ℃/min and 3.3 ℃/h were conducted. The temperature was raised at different points of the explosive and the strains at different points of the shell were obtained. The intensity of the shock wave in the process of the slow cook-off experiment is calculated by using the thin-walled cylinder principle, and the violence of the reaction of the JH-14C booster explosive with a shell is quantitatively characterized by using the intensity of blast loading. The response characteristics of the JH-14C booster explosive with a shell in the slow cook-off experiment is revealed. Though the relationship between the shell strain results and the reaction intensities, a method is proposed to describe the reaction level of the JH-14C booster explosive with a shell. Based on the thermodynamics and the chemical reaction of the explosive, the heat conduction model is established. The decomposition reaction of the explosive is described by the Arrhenius equation. A back propagation (BP) neural network is used to invert the heat reaction parameters of the JH-14C booster explosive. Comparison between the experimental and simulated results shows that the presented model can be used to obtain the cook-off response characteristics of the explosive obtained by simulation with high precision. The internal temperature field response of the projectile body is also studied under different heating rates. The results exhibit that the lower the heating rate, the higher the response temperature of the charge and the more intense the reaction. With the decrease of the heating rate, the ignition area of the explosive gradually shifts from the outer edges of both ends to the inside of the explosive.
In order to explore the cook-off response characteristics of the JH-14C booster explosive with a shell under different external temperatures, a set of experimental devices was designed for measuring the cook-off response temperatures at multiple points of the JH-14C booster explosive and for monitoring the deformation of the shell. The explosive temperatures were measured from its edge to its center. The strain-time curves of the shell were recorded by a dynamic strain indicator and a high-temperature strain gauge. The cook-off experiments with the heating rates of 1.0 ℃/min and 3.3 ℃/h were conducted. The temperature was raised at different points of the explosive and the strains at different points of the shell were obtained. The intensity of the shock wave in the process of the slow cook-off experiment is calculated by using the thin-walled cylinder principle, and the violence of the reaction of the JH-14C booster explosive with a shell is quantitatively characterized by using the intensity of blast loading. The response characteristics of the JH-14C booster explosive with a shell in the slow cook-off experiment is revealed. Though the relationship between the shell strain results and the reaction intensities, a method is proposed to describe the reaction level of the JH-14C booster explosive with a shell. Based on the thermodynamics and the chemical reaction of the explosive, the heat conduction model is established. The decomposition reaction of the explosive is described by the Arrhenius equation. A back propagation (BP) neural network is used to invert the heat reaction parameters of the JH-14C booster explosive. Comparison between the experimental and simulated results shows that the presented model can be used to obtain the cook-off response characteristics of the explosive obtained by simulation with high precision. The internal temperature field response of the projectile body is also studied under different heating rates. The results exhibit that the lower the heating rate, the higher the response temperature of the charge and the more intense the reaction. With the decrease of the heating rate, the ignition area of the explosive gradually shifts from the outer edges of both ends to the inside of the explosive.
2023, 43(7): 072302.
doi: 10.11883/bzycj-2022-0452
Abstract:
A device was developed to experimentally explore the influences of the ignition energy on the combustion and explosion characteristics of single-base propellant. In order to control the ignition energy on the single-base propellant, the black powders with different masses were used to ignite the propellant in the combustion and explosion experiment. By analyzing the ablative traces on the inner wall of the witness plate and the confining steel cylinder, the combustion and explosion development process of the single-base propellant was discussed, and the influences of different ignition energies on the combustion and explosion characteristics of the single-base-propellant were obtained. The results show that, at the beginning of ignition, the combustion reaction of the propellant in the confining steel cylinder is incomplete and the reaction is weak according to the larger ablation trace diameter and lighter ablation trace color. After propagating a distance away from the ignition side, the combustion reaction becomes stronger, but the reaction is still incomplete at this time, smaller ablation diameter and deeper ablation color. While propagating to the end of the confinging steel cylinder, the propellant reaction is complete and the severity of reaction is relatively large, seen from the smaller ablation diameter and the lighter ablation color. At the ignition energies of 4.0, 5.0 and 8.0 kJ, the growth distances from initial ignition to rapid increase of reaction intensity were 54.66, 53.95 and 19.38 cm, respectively. At the ignition energy of 20.0 kJ, the propellant reaction is already strong at the beginning and grows stronger enough to produce obvious dents on the witness plate while propagating to the end. Also at this ignition energy, slow combustion, fast combustion and deflagration occur in the reacion of the propellant, respectively at different positions in the confining steel cylinder. The study enlights that the ignition energy has reference significance for the design of propellant charge.
A device was developed to experimentally explore the influences of the ignition energy on the combustion and explosion characteristics of single-base propellant. In order to control the ignition energy on the single-base propellant, the black powders with different masses were used to ignite the propellant in the combustion and explosion experiment. By analyzing the ablative traces on the inner wall of the witness plate and the confining steel cylinder, the combustion and explosion development process of the single-base propellant was discussed, and the influences of different ignition energies on the combustion and explosion characteristics of the single-base-propellant were obtained. The results show that, at the beginning of ignition, the combustion reaction of the propellant in the confining steel cylinder is incomplete and the reaction is weak according to the larger ablation trace diameter and lighter ablation trace color. After propagating a distance away from the ignition side, the combustion reaction becomes stronger, but the reaction is still incomplete at this time, smaller ablation diameter and deeper ablation color. While propagating to the end of the confinging steel cylinder, the propellant reaction is complete and the severity of reaction is relatively large, seen from the smaller ablation diameter and the lighter ablation color. At the ignition energies of 4.0, 5.0 and 8.0 kJ, the growth distances from initial ignition to rapid increase of reaction intensity were 54.66, 53.95 and 19.38 cm, respectively. At the ignition energy of 20.0 kJ, the propellant reaction is already strong at the beginning and grows stronger enough to produce obvious dents on the witness plate while propagating to the end. Also at this ignition energy, slow combustion, fast combustion and deflagration occur in the reacion of the propellant, respectively at different positions in the confining steel cylinder. The study enlights that the ignition energy has reference significance for the design of propellant charge.
2023, 43(7): 073101.
doi: 10.11883/bzycj-2022-0525
Abstract:
Ω-shaped composite tubes have certain application potential in terms of collision energy absorption and lightweight. To study the effects of ply orientation and loading rate on the energy absorption characteristics of the Ω-shaped composite tubes, quasi-static and dynamic axial compression experiments were carried out on carbon-fiber-reinforced composite Ω-shaped tubes by using an electronic universal testing machine and a high-speed hydraulic servo testing machine, respectively. In addition, the failure modes and evaluation index relevant to energy absorption were analyzed based on the crushing load-displacement curves and failure morphologies. In the experiments, the Ω-shaped tubes with three ply orientations, namely [0/90]3s, [0/45/90/−45]3 and [±45]3s, were compressed under quasi-static and dynamic loading rates. Under quasi-static loading, the specimens with [0/90]3s and [0/45/90/−45]3 ply orientations both showed progressive failure, while the specimens with [±45]3s ply orientation showed a catastrophic failure mode. The specific energy absorption (SEA) of the specimens with [±45]3s ply orientation is about half of those of the other two specimens due to different failure modes. Under the dynamic loading, the Ω-shaped tubes with three ply orientations, where the SEA almost remains the same, were all featured by the progressive crushing. Moreover, the SEAs of the specimens with [0/90]3s and [0/45/90/−45]3 ply orientations under dynamic loading are reduced by 29.70% and 20.97%, respectively, compared with those under quasi-static loading. However, the SEA of the specimens with [±45]3s ply orientation is 46.10% higher than that under quasi-static loading. The change of failure modes is the main reason for the increase of the SEA. Under quasi-static loading, the ply orientation has a certain effect on the SEA of the Ω-shaped tube, while under dynamic loading, its influence is relatively weak. The main reasons are as follows. Under a low loading rate, buckling fracture and interlaminar delamination of fiber and matrix gradually occur, resulting in a global response of the structure. On the other hand, under a higher loading rate, the contact time between the Ω-shaped tubes and the indenter is short, leading to a localized response, which is dominated by the loading rate, while the failure mode is less affected by the ply orientations.
Ω-shaped composite tubes have certain application potential in terms of collision energy absorption and lightweight. To study the effects of ply orientation and loading rate on the energy absorption characteristics of the Ω-shaped composite tubes, quasi-static and dynamic axial compression experiments were carried out on carbon-fiber-reinforced composite Ω-shaped tubes by using an electronic universal testing machine and a high-speed hydraulic servo testing machine, respectively. In addition, the failure modes and evaluation index relevant to energy absorption were analyzed based on the crushing load-displacement curves and failure morphologies. In the experiments, the Ω-shaped tubes with three ply orientations, namely [0/90]3s, [0/45/90/−45]3 and [±45]3s, were compressed under quasi-static and dynamic loading rates. Under quasi-static loading, the specimens with [0/90]3s and [0/45/90/−45]3 ply orientations both showed progressive failure, while the specimens with [±45]3s ply orientation showed a catastrophic failure mode. The specific energy absorption (SEA) of the specimens with [±45]3s ply orientation is about half of those of the other two specimens due to different failure modes. Under the dynamic loading, the Ω-shaped tubes with three ply orientations, where the SEA almost remains the same, were all featured by the progressive crushing. Moreover, the SEAs of the specimens with [0/90]3s and [0/45/90/−45]3 ply orientations under dynamic loading are reduced by 29.70% and 20.97%, respectively, compared with those under quasi-static loading. However, the SEA of the specimens with [±45]3s ply orientation is 46.10% higher than that under quasi-static loading. The change of failure modes is the main reason for the increase of the SEA. Under quasi-static loading, the ply orientation has a certain effect on the SEA of the Ω-shaped tube, while under dynamic loading, its influence is relatively weak. The main reasons are as follows. Under a low loading rate, buckling fracture and interlaminar delamination of fiber and matrix gradually occur, resulting in a global response of the structure. On the other hand, under a higher loading rate, the contact time between the Ω-shaped tubes and the indenter is short, leading to a localized response, which is dominated by the loading rate, while the failure mode is less affected by the ply orientations.
2023, 43(7): 073102.
doi: 10.11883/bzycj-2022-0493
Abstract:
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Adiabatic shearing is a common failure mechanism for additively manufactured metals and alloys under dynamic loads. Cylindrical samples (
2023, 43(7): 073103.
doi: 10.11883/bzycj-2023-0019
Abstract:
In order to study the dynamic response of a sandwich panel cored by butterfly-shaped honeycomb with negative Poisson’s ratio to low-velocity impact, a mass-spring (MS) model is applied to obtain the contact force between the spherical impactor and the honeycomb sandwich panel. Meanwhile, based on the Hamilton’s principle and the first-order shear deformation theory, the equation of motion for the butterfly-shaped honeycomb sandwich panel with negative Poisson’s ratio is derived. Besides, the Navier method and Duhamel’s integral are used to solve the vibration displacement of the honeycomb sandwich panel. To validate the theoretical model, the results are compared with the results of ABAQUS’ numerical simulation or published literature. It is shown that the maximum relative error between the numerical modeling results of the first five order natural frequencies and the results of theoretical model calculated in this paper is 6.52%, the maximum relative error between the numerical modeling results of the honeycomb sandwich panel under low-velocity impact and the calculated results of the theoretical model in this paper is 6.84%, and the maximum relative error of the contact force between the theoretical model in this paper and the published studies is 8%, thus verifying the validity of the theoretical model. The results show that the maximum lateral displacement of the honeycomb sandwich panel increases with the increasing velocity of the spherical impactor. Under the same impact load, the impact resistance of the honeycomb sandwich panel increases with the increase of the wall thickness of the unit cell, and decreases with the increase of the unit cell angle. The impact resistance of the honeycomb sandwich panel increases by 3.7% when the thickness of the unit cell wall changes from 1 mm to 3 mm. The lateral displacement of the butterfly-shaped honeycomb sandwich panel decreases while the contact force between the impactor and the honeycomb sandwich panel increases with the increase of the length-width ratio and the height ratio. When the width-length ratio of the honeycomb sandwich panel changes from 1∶1 to 1∶2, the maximum lateral displacement of the honeycomb sandwich panel decreases by 6.1%, and when the height ratio of the top skin layer to the honeycomb core layer changes from 1∶6 to 1∶14, the maximum lateral displacement of the honeycomb sandwich panel decreases by 5.4%, which indicates that the impact resistance of the honeycomb sandwich panel is enhanced and the energy absorption effect is obvious.
In order to study the dynamic response of a sandwich panel cored by butterfly-shaped honeycomb with negative Poisson’s ratio to low-velocity impact, a mass-spring (MS) model is applied to obtain the contact force between the spherical impactor and the honeycomb sandwich panel. Meanwhile, based on the Hamilton’s principle and the first-order shear deformation theory, the equation of motion for the butterfly-shaped honeycomb sandwich panel with negative Poisson’s ratio is derived. Besides, the Navier method and Duhamel’s integral are used to solve the vibration displacement of the honeycomb sandwich panel. To validate the theoretical model, the results are compared with the results of ABAQUS’ numerical simulation or published literature. It is shown that the maximum relative error between the numerical modeling results of the first five order natural frequencies and the results of theoretical model calculated in this paper is 6.52%, the maximum relative error between the numerical modeling results of the honeycomb sandwich panel under low-velocity impact and the calculated results of the theoretical model in this paper is 6.84%, and the maximum relative error of the contact force between the theoretical model in this paper and the published studies is 8%, thus verifying the validity of the theoretical model. The results show that the maximum lateral displacement of the honeycomb sandwich panel increases with the increasing velocity of the spherical impactor. Under the same impact load, the impact resistance of the honeycomb sandwich panel increases with the increase of the wall thickness of the unit cell, and decreases with the increase of the unit cell angle. The impact resistance of the honeycomb sandwich panel increases by 3.7% when the thickness of the unit cell wall changes from 1 mm to 3 mm. The lateral displacement of the butterfly-shaped honeycomb sandwich panel decreases while the contact force between the impactor and the honeycomb sandwich panel increases with the increase of the length-width ratio and the height ratio. When the width-length ratio of the honeycomb sandwich panel changes from 1∶1 to 1∶2, the maximum lateral displacement of the honeycomb sandwich panel decreases by 6.1%, and when the height ratio of the top skin layer to the honeycomb core layer changes from 1∶6 to 1∶14, the maximum lateral displacement of the honeycomb sandwich panel decreases by 5.4%, which indicates that the impact resistance of the honeycomb sandwich panel is enhanced and the energy absorption effect is obvious.
2023, 43(7): 073104.
doi: 10.11883/bzycj-2022-0254
Abstract:
As a traditional energy absorbing and shock absorbing protective material, polyurethane has high requirements for its dynamic mechanical properties. An effective way to improve the impact resistance of polyurethane is to add ceramic balls as reinforcement in polyurethane matrix. The existing research on ceramic ball reinforced materials mainly focuses on nano and micro scale. The dynamic response of Al2O3 ceramic ball reinforced polyurethane matrix composites under small equivalent explosion load was simulated by establishing a numerical model of polyurethane embedded millimeter ceramic ball and using ALE algorithm of LS-DYNA and the correctness of the numerical model was verified by the empirical formula of henrych’s free field explosion overpressure and the penetration experiment of polyurethane-ceramic sphere composite plate. The deformation process of the composite plate was obtained and through the comparison of the acceleration of the composite plate and the pure polyurethane, it was found that the acceleration of the ceramic ball and the polyurethane always maintain the opposite direction, which proves that the existence of the ceramic ball reduces the overall acceleration fluctuation range; Furthermore, the effects of explosion equivalent on the velocity, displacement and energy absorption of composite plates and the effects of different explosion equivalent and ceramic ball size on the properties of composite materials under a certain areal density were discussed. The results show that the overall acceleration fluctuation range of polyurethane-ceramic balls composite material is about 1×105 m/s2 lower than that of pure polyurethane. With the increase of explosive equivalent, the deflection of the composite increased steadily to 1 mm, and the energy absorption proportion of polyurethane increased from 69.6% to 80.3%. Under the same areal density, both the deformation resistance of the composite plate and the overall acceleration fluctuation range increases with the increase of the diameter of the ceramic ball.
As a traditional energy absorbing and shock absorbing protective material, polyurethane has high requirements for its dynamic mechanical properties. An effective way to improve the impact resistance of polyurethane is to add ceramic balls as reinforcement in polyurethane matrix. The existing research on ceramic ball reinforced materials mainly focuses on nano and micro scale. The dynamic response of Al2O3 ceramic ball reinforced polyurethane matrix composites under small equivalent explosion load was simulated by establishing a numerical model of polyurethane embedded millimeter ceramic ball and using ALE algorithm of LS-DYNA and the correctness of the numerical model was verified by the empirical formula of henrych’s free field explosion overpressure and the penetration experiment of polyurethane-ceramic sphere composite plate. The deformation process of the composite plate was obtained and through the comparison of the acceleration of the composite plate and the pure polyurethane, it was found that the acceleration of the ceramic ball and the polyurethane always maintain the opposite direction, which proves that the existence of the ceramic ball reduces the overall acceleration fluctuation range; Furthermore, the effects of explosion equivalent on the velocity, displacement and energy absorption of composite plates and the effects of different explosion equivalent and ceramic ball size on the properties of composite materials under a certain areal density were discussed. The results show that the overall acceleration fluctuation range of polyurethane-ceramic balls composite material is about 1×105 m/s2 lower than that of pure polyurethane. With the increase of explosive equivalent, the deflection of the composite increased steadily to 1 mm, and the energy absorption proportion of polyurethane increased from 69.6% to 80.3%. Under the same areal density, both the deformation resistance of the composite plate and the overall acceleration fluctuation range increases with the increase of the diameter of the ceramic ball.
2023, 43(7): 073201.
doi: 10.11883/bzycj-2022-0538
Abstract:
Contact explosion experiments were conducted to assess the damage capacity of a cylindrical charge contact explosion on a concrete obstacle. A characterization method for the damage level of a concrete obstacle was proposed based on the experimental results. Subsequently, numerical simulations were performed to study the influence of charge mass and placement location on the residual height of a concrete obstacle. To validate the numerical model and applied material parameters, the results of the numerical simulations were compared with the experimental results. Based on the numerical results, the vulnerability of the concrete obstacle under contact explosions of different charge placements was characterized using the damage iso-curve method. The shape and center position of the damage zone on the top and side of the obstacle were obtained. Considering the randomness of charge placement after deployment in actual use, a model for calculating the vulnerable area was established to investigate the overall vulnerability of the obstacle. The relationship between the charge mass and the vulnerable area of different damage levels of the obstacle when the charge exploded on the top and side was obtained. The research results indicate that the shape of the damage zone on the top of the obstacle is approximately a square, with the center coinciding with the center of the top surface. The shape of the damage zone on the side is approximately a rounded trapezoid, with the center located about 10 cm below the geometric center of the side surface. Based on the calculated results of the vulnerable area, the difference in vulnerability between the top and side of the obstacle under contact explosion was compared. When the mass of the cylindrical charge is between 0.5 kg and 10.79 kg, the concrete obstacle is more vulnerable to damage when subjected to a contact explosion on the side. The findings of this research can provide support and guidance for the demolition of concrete obstacles, the design of obstacle-breaking projectiles, and the evaluation of their damage effectiveness.
Contact explosion experiments were conducted to assess the damage capacity of a cylindrical charge contact explosion on a concrete obstacle. A characterization method for the damage level of a concrete obstacle was proposed based on the experimental results. Subsequently, numerical simulations were performed to study the influence of charge mass and placement location on the residual height of a concrete obstacle. To validate the numerical model and applied material parameters, the results of the numerical simulations were compared with the experimental results. Based on the numerical results, the vulnerability of the concrete obstacle under contact explosions of different charge placements was characterized using the damage iso-curve method. The shape and center position of the damage zone on the top and side of the obstacle were obtained. Considering the randomness of charge placement after deployment in actual use, a model for calculating the vulnerable area was established to investigate the overall vulnerability of the obstacle. The relationship between the charge mass and the vulnerable area of different damage levels of the obstacle when the charge exploded on the top and side was obtained. The research results indicate that the shape of the damage zone on the top of the obstacle is approximately a square, with the center coinciding with the center of the top surface. The shape of the damage zone on the side is approximately a rounded trapezoid, with the center located about 10 cm below the geometric center of the side surface. Based on the calculated results of the vulnerable area, the difference in vulnerability between the top and side of the obstacle under contact explosion was compared. When the mass of the cylindrical charge is between 0.5 kg and 10.79 kg, the concrete obstacle is more vulnerable to damage when subjected to a contact explosion on the side. The findings of this research can provide support and guidance for the demolition of concrete obstacles, the design of obstacle-breaking projectiles, and the evaluation of their damage effectiveness.
2023, 43(7): 073301.
doi: 10.11883/bzycj-2022-0275
Abstract:
In order to gain insight into the mechanism of catastrophic damage due to the hydrodynamic ram effect caused by projectiles with high-velocity striking fluid-filled containers such as aircraft fuel tanks, an ballistic shock experiment was carried out by using projectiles to penetrate riveted fuel tanks. The dynamic responses of the rear wall were observed with a three-dimensional digital image correlation technique, and the experimental data were obtained, such as the deformations of the tanks and the diameters of the hole under projectile impact. Also, the fluid-solid coupling finite element model was established based on the experiment to simulate the impact process and the hydrodynamic ram effect under the projectile velocity from 780 to 1600 m/s by analyzing the variation of projectile velocities influencing the kinetic energy reductions, projectile accelerations, the distribution of liquid pressure in the box and the deformation and tearing of the tank wall and rivets. The results show that the finite element simulation results are consistent with the experimental ones. The kinetic energy loss of the projectile, the deformation of the tank, and the peak pressure of the fuel are proportional to the projectile velocity. When the projectile velocity reached 1400 m/s, cracks began to appear on the rear wall of the fuel tank, showing a petal-type hole damage. When the projectile velocity reached 1600 m/s, the rivet began to break.
In order to gain insight into the mechanism of catastrophic damage due to the hydrodynamic ram effect caused by projectiles with high-velocity striking fluid-filled containers such as aircraft fuel tanks, an ballistic shock experiment was carried out by using projectiles to penetrate riveted fuel tanks. The dynamic responses of the rear wall were observed with a three-dimensional digital image correlation technique, and the experimental data were obtained, such as the deformations of the tanks and the diameters of the hole under projectile impact. Also, the fluid-solid coupling finite element model was established based on the experiment to simulate the impact process and the hydrodynamic ram effect under the projectile velocity from 780 to 1600 m/s by analyzing the variation of projectile velocities influencing the kinetic energy reductions, projectile accelerations, the distribution of liquid pressure in the box and the deformation and tearing of the tank wall and rivets. The results show that the finite element simulation results are consistent with the experimental ones. The kinetic energy loss of the projectile, the deformation of the tank, and the peak pressure of the fuel are proportional to the projectile velocity. When the projectile velocity reached 1400 m/s, cracks began to appear on the rear wall of the fuel tank, showing a petal-type hole damage. When the projectile velocity reached 1600 m/s, the rivet began to break.
2023, 43(7): 073302.
doi: 10.11883/bzycj-2022-0266
Abstract:
Based on high-speed photography technology, the oblique water-entry experiments of high-speed projectile under multiple conditions are carried out. During the experiment, five experiments were conducted for each condition, and the same phenomenon appeared in the experiment. A self-programing is utilized to capture the image’s pixels and extract the experimental data for the experimental photographs. By analyzing the formation, development, and collapse processes of the oblique water-entry cavity of high-speed projectile, the evolution characteristics of projectile cavitation during tail-slapping are concluded. In addition, by comparing and analyzing the variations of the cavity size, and the velocity and acceleration of projectiles with different initial velocities of the water-entry of the projectile, the influence of the initial velocities of the water-entry of the projectile on cavitation evolution characteristics and water-entry motion traits is summarized. The results show that after the tail-slapping of the projectile, part of the projectile tail penetrates through the original cavity and gets wet, and a new tail-slapping cavity is generated backward from the projectile tail. The tail-slapping cavity fits closely with the original cavity. At the end of the tail-slapping, the location of the tail-slapping cavity under the water is basically unchanged. The tail-slapping cavity is pulled away from the surface of the original cavity of the projectile and collapses, while the original cavity at the same depth accelerates and collapses under the influence of the jet generated by the tail-slapping. With the increase of the initial velocities of the water-entry of the projectile, the size of the tail-slapping cavity and the length of the original gradually increase, and so does the maximum wet area of the tail. With the increase of the number of tail-slapping, the velocity attenuation amplitude and the energy loss of the projectile in each tail-slapping increase, and the capacity of the speed storage of the projectile decreases.
Based on high-speed photography technology, the oblique water-entry experiments of high-speed projectile under multiple conditions are carried out. During the experiment, five experiments were conducted for each condition, and the same phenomenon appeared in the experiment. A self-programing is utilized to capture the image’s pixels and extract the experimental data for the experimental photographs. By analyzing the formation, development, and collapse processes of the oblique water-entry cavity of high-speed projectile, the evolution characteristics of projectile cavitation during tail-slapping are concluded. In addition, by comparing and analyzing the variations of the cavity size, and the velocity and acceleration of projectiles with different initial velocities of the water-entry of the projectile, the influence of the initial velocities of the water-entry of the projectile on cavitation evolution characteristics and water-entry motion traits is summarized. The results show that after the tail-slapping of the projectile, part of the projectile tail penetrates through the original cavity and gets wet, and a new tail-slapping cavity is generated backward from the projectile tail. The tail-slapping cavity fits closely with the original cavity. At the end of the tail-slapping, the location of the tail-slapping cavity under the water is basically unchanged. The tail-slapping cavity is pulled away from the surface of the original cavity of the projectile and collapses, while the original cavity at the same depth accelerates and collapses under the influence of the jet generated by the tail-slapping. With the increase of the initial velocities of the water-entry of the projectile, the size of the tail-slapping cavity and the length of the original gradually increase, and so does the maximum wet area of the tail. With the increase of the number of tail-slapping, the velocity attenuation amplitude and the energy loss of the projectile in each tail-slapping increase, and the capacity of the speed storage of the projectile decreases.
2023, 43(7): 073303.
doi: 10.11883/bzycj-2022-0506
Abstract:
The torpedo may be damaged by impact while entering the water. Due to changes in shape, the place where cabins are connected is more stressed and is usually more dangerous. The trajectory of a torpedo is stable when it enters the water vertically for a short time. Based on this, the axial motion and mechanical characteristics of the torpedo’s cabins and connecting parts were studied. Firstly, the arbitrary Lagrangian-Eulerian (ALE) algorithm and penalty function method were used to establish the numerical model of fluid-structure coupling calculation, and its effectiveness was then verified by comparing it with the existing experiment. Next, four sets of solid grids and five sets of fluid grids were established, and the changes of the maximum acceleration and the maximum pressure were analyzed. The independence of the grid was verified through comparison. The vertical water-entry processes of the torpedoes with different head shapes and connection forms were simulated and compared with those of integral torpedoes. The results show that the acceleration increases instantaneously after the torpedo hits the water, then fluctuates in the positive and negative directions around zero and becomes smaller and smaller. The sharper the head, the weaker the impact. The response characteristics of each cabin are different. Since the stress is transmitted backward in the form of waves, the response order of each cabin depends on the distance from the head, and the strength will gradually decrease. The adjacent shells are no longer relatively stationary, and the connector between them will be continuously pulled and pressed, leading to significant changes in their appearances and positions. When the adjacent shells tend to move away from each other, there will be gaps, and the stress of the connectors will also reach the maximum, which is dangerous to the torpedo. It is recommended to add sealing rings or other fixed devices in the project to strengthen the protection of connection parts.
The torpedo may be damaged by impact while entering the water. Due to changes in shape, the place where cabins are connected is more stressed and is usually more dangerous. The trajectory of a torpedo is stable when it enters the water vertically for a short time. Based on this, the axial motion and mechanical characteristics of the torpedo’s cabins and connecting parts were studied. Firstly, the arbitrary Lagrangian-Eulerian (ALE) algorithm and penalty function method were used to establish the numerical model of fluid-structure coupling calculation, and its effectiveness was then verified by comparing it with the existing experiment. Next, four sets of solid grids and five sets of fluid grids were established, and the changes of the maximum acceleration and the maximum pressure were analyzed. The independence of the grid was verified through comparison. The vertical water-entry processes of the torpedoes with different head shapes and connection forms were simulated and compared with those of integral torpedoes. The results show that the acceleration increases instantaneously after the torpedo hits the water, then fluctuates in the positive and negative directions around zero and becomes smaller and smaller. The sharper the head, the weaker the impact. The response characteristics of each cabin are different. Since the stress is transmitted backward in the form of waves, the response order of each cabin depends on the distance from the head, and the strength will gradually decrease. The adjacent shells are no longer relatively stationary, and the connector between them will be continuously pulled and pressed, leading to significant changes in their appearances and positions. When the adjacent shells tend to move away from each other, there will be gaps, and the stress of the connectors will also reach the maximum, which is dangerous to the torpedo. It is recommended to add sealing rings or other fixed devices in the project to strengthen the protection of connection parts.
2023, 43(7): 074101.
doi: 10.11883/bzycj-2023-0007
Abstract:
The triaxial accelerometer can simultaneously detect and measure shock loads along the three coordinate axes in the three-dimensional space. Therefore, it has a wide range of applications in the fields of spatial vibration test, spatial impact test, and so on. Before being put into practical use, triaxial accelerometers must be calibrated for their sensitivity coefficients to ensure the validity and accuracy of measurements. Unlike the calibration of single-axis accelerometers, there is a major difficulty in the calibration technologies of the triaxial accelerometers, that is, how to realize the excitation of three-dimensional shock loads synchronously, since the pulse width of the shock loads are usually as short as a few milliseconds. On the other hand, tracing and measuring the acceleration excited during shock process is also the key to the shock calibration of accelerometers. In order to address the aforementioned problems, a drop table equipped with a shock amplifier was used to excite acceleration loads vertically upward. Then, with the help of an anvil which has a bevel, the vertical acceleration excited on shock amplifier was decomposed to each sensitive axis of the triaxial accelerometer based the principle of vector decomposition. By means of this approach, synchronous shock loading of the triaxial accelerometer was then realized. High-speed camera and image processing based on MATLAB were used to trace and measure the acceleration excited in the synchronous shock calibration of triaxial accelerometers. Experiments were conducted to verify the effectiveness of the motion measurement method based on high-speed camera and MATLAB image processing. The sensitivity matrix of the triaxial accelerometer, which takes into consideration both the main sensitivity coefficients and the coupling sensitivity coefficients, was solved using the least-square method. At last, the measurement accuracy of the accelerometer calibrated using the synchronous method was compared with the measurement accuracy of the accelerometer calibrated using the conventional asynchronous method. The research results indicate that the conventional drop table could excite a wide range (102g~104g) of acceleration by equipping a shock amplifier. In addition, the motion measurement method based on high-speed camera and MATLAB image processing is valid in acceleration traceability or measurement in the shock calibration of accelerometer. Furthermore, compared to the measurement accuracy of the accelerometer calibrated by the asynchronous method, the measurement accuracy of the triaxial accelerometer could be guaranteed and improved by using the synchronous method. Therefore, in engineering, the triaxial accelerometer ought to be calibrated using synchronous methods rather than asynchronous methods to guarantee the validity and accuracy of measurements.
The triaxial accelerometer can simultaneously detect and measure shock loads along the three coordinate axes in the three-dimensional space. Therefore, it has a wide range of applications in the fields of spatial vibration test, spatial impact test, and so on. Before being put into practical use, triaxial accelerometers must be calibrated for their sensitivity coefficients to ensure the validity and accuracy of measurements. Unlike the calibration of single-axis accelerometers, there is a major difficulty in the calibration technologies of the triaxial accelerometers, that is, how to realize the excitation of three-dimensional shock loads synchronously, since the pulse width of the shock loads are usually as short as a few milliseconds. On the other hand, tracing and measuring the acceleration excited during shock process is also the key to the shock calibration of accelerometers. In order to address the aforementioned problems, a drop table equipped with a shock amplifier was used to excite acceleration loads vertically upward. Then, with the help of an anvil which has a bevel, the vertical acceleration excited on shock amplifier was decomposed to each sensitive axis of the triaxial accelerometer based the principle of vector decomposition. By means of this approach, synchronous shock loading of the triaxial accelerometer was then realized. High-speed camera and image processing based on MATLAB were used to trace and measure the acceleration excited in the synchronous shock calibration of triaxial accelerometers. Experiments were conducted to verify the effectiveness of the motion measurement method based on high-speed camera and MATLAB image processing. The sensitivity matrix of the triaxial accelerometer, which takes into consideration both the main sensitivity coefficients and the coupling sensitivity coefficients, was solved using the least-square method. At last, the measurement accuracy of the accelerometer calibrated using the synchronous method was compared with the measurement accuracy of the accelerometer calibrated using the conventional asynchronous method. The research results indicate that the conventional drop table could excite a wide range (102g~104g) of acceleration by equipping a shock amplifier. In addition, the motion measurement method based on high-speed camera and MATLAB image processing is valid in acceleration traceability or measurement in the shock calibration of accelerometer. Furthermore, compared to the measurement accuracy of the accelerometer calibrated by the asynchronous method, the measurement accuracy of the triaxial accelerometer could be guaranteed and improved by using the synchronous method. Therefore, in engineering, the triaxial accelerometer ought to be calibrated using synchronous methods rather than asynchronous methods to guarantee the validity and accuracy of measurements.
2023, 43(7): 074102.
doi: 10.11883/bzycj-2022-0392
Abstract:
In recent years, the new measurement method of shock wave reflection overpressure peak by using the direct proportional relationship between the pressure to be measured and the diaphragm acceleration has been verified by shock-tube verification experiments. This method has the advantages of no calibration, simple fabrication, low cost and high measurement accuracy. In order to optimize the main parameters of the thin-diaphragm pressure sensor and to obtain the uncertainty of pressure measurement, numerical simulations were carried out. Specifically, the numerical simulation based on step pressure was carried out to analyze the influences of diaphragm thickness, pressure to be measured, fitting parameters and other factors on the pressure measurement. The numerical simulation based on blast pressure was carried out to analyze the influence of rapid pressure drop on measurement. The displacement or velocity signal of the thin diaphragm was fitted to obtain the diaphragm’s acceleration value at the beginning of impact, which was further used to calculate the pressure peak to be measured. By comparing the calculated pressure with the standard pressure, the optimum values of fitting time, fitting polynomial degree, diaphragm thickness and other factors were obtained. And the main technical specifications of the thin diaphragm pressure sensor were obtained. In particular, the polynomial fitting method was applied to carry out data processing, which can effectively avoid the model error introduced by linear fitting. This method obviously improved the measurement accuracy of the sensor and was a great improvement. In addition, shock-tube experiments were carried out to verify some conclusions by numerical simulation. In summary, the optimal parameters of the diaphragm pressure sensor were obtained: the thickness of the stainless steel diaphragm is 50－70 µm, velocity data is fitted by second-order polynomial, and fitting time is about 0.8 µs. And the relative error of shock wave reflection overpressure peak measurement can be controlled within 3%. Relevant conclusions can provide references for the popularization and application of the diaphragm pressure sensors.
In recent years, the new measurement method of shock wave reflection overpressure peak by using the direct proportional relationship between the pressure to be measured and the diaphragm acceleration has been verified by shock-tube verification experiments. This method has the advantages of no calibration, simple fabrication, low cost and high measurement accuracy. In order to optimize the main parameters of the thin-diaphragm pressure sensor and to obtain the uncertainty of pressure measurement, numerical simulations were carried out. Specifically, the numerical simulation based on step pressure was carried out to analyze the influences of diaphragm thickness, pressure to be measured, fitting parameters and other factors on the pressure measurement. The numerical simulation based on blast pressure was carried out to analyze the influence of rapid pressure drop on measurement. The displacement or velocity signal of the thin diaphragm was fitted to obtain the diaphragm’s acceleration value at the beginning of impact, which was further used to calculate the pressure peak to be measured. By comparing the calculated pressure with the standard pressure, the optimum values of fitting time, fitting polynomial degree, diaphragm thickness and other factors were obtained. And the main technical specifications of the thin diaphragm pressure sensor were obtained. In particular, the polynomial fitting method was applied to carry out data processing, which can effectively avoid the model error introduced by linear fitting. This method obviously improved the measurement accuracy of the sensor and was a great improvement. In addition, shock-tube experiments were carried out to verify some conclusions by numerical simulation. In summary, the optimal parameters of the diaphragm pressure sensor were obtained: the thickness of the stainless steel diaphragm is 50－70 µm, velocity data is fitted by second-order polynomial, and fitting time is about 0.8 µs. And the relative error of shock wave reflection overpressure peak measurement can be controlled within 3%. Relevant conclusions can provide references for the popularization and application of the diaphragm pressure sensors.
