2006 Vol. 26, No. 2
Display Method:
2006, 26(2): 97-104.
doi: 10.11883/1001-1455(2006)02-0097-08
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Abstract:
Assuming that the main effect of the voids is to reduce the area over which the stress acts in the early stage and the stress decreases to porosity-dependent value in the void coalescence stages, the stress relaxation equations in the spall process are given and a void coalescence-based spall model is proposed. The stress(or pressure)-dependent spall porosities given by Thomason, Tonks, et al and Cochran et al are respectively combined with conservation equations, equation of state and constitutive equations for the damaged aggregate to establish a series of close equations for all variables including damage. The void coalescence-based spall model is applied to numerical simulations of one-dimensional spall tests. The spall strength and the critical damage in the proposed spall model can be initially estimated and final determination of them should make the calcualted results of spall test under initial and boundary conditions consistent with the experimental velocity(stress) profile and the observed damage at spall plane. The calculated results based on the pressure-dependent spall porosities given by Tonk et al and Cochran et al are consistent but different from the calculated results based on Thomasons stress-dependent spall porosity.
Assuming that the main effect of the voids is to reduce the area over which the stress acts in the early stage and the stress decreases to porosity-dependent value in the void coalescence stages, the stress relaxation equations in the spall process are given and a void coalescence-based spall model is proposed. The stress(or pressure)-dependent spall porosities given by Thomason, Tonks, et al and Cochran et al are respectively combined with conservation equations, equation of state and constitutive equations for the damaged aggregate to establish a series of close equations for all variables including damage. The void coalescence-based spall model is applied to numerical simulations of one-dimensional spall tests. The spall strength and the critical damage in the proposed spall model can be initially estimated and final determination of them should make the calcualted results of spall test under initial and boundary conditions consistent with the experimental velocity(stress) profile and the observed damage at spall plane. The calculated results based on the pressure-dependent spall porosities given by Tonk et al and Cochran et al are consistent but different from the calculated results based on Thomasons stress-dependent spall porosity.
2006, 26(2): 105-214.
doi: 10.11883/1001-1455(2006)02-0105-10
Abstract:
The normal and oblique penetration tests of reduced-scale earth penetrating weapon(EPW) are conducted. Various projectile structures and concrete targets as well as the experimental method are designed. The impact velocities vary in the range of 620～820 m/s, and the integrity of projectile structures are clarified. A large amount of experimental results of normal/oblique penetrations are summarized and the theoretical analyses are further conducted on the impact appearance, terminal ballistic effect and the damage of projectile bodies, etc.
The normal and oblique penetration tests of reduced-scale earth penetrating weapon(EPW) are conducted. Various projectile structures and concrete targets as well as the experimental method are designed. The impact velocities vary in the range of 620～820 m/s, and the integrity of projectile structures are clarified. A large amount of experimental results of normal/oblique penetrations are summarized and the theoretical analyses are further conducted on the impact appearance, terminal ballistic effect and the damage of projectile bodies, etc.
2006, 26(2): 115-120.
doi: 10.11883/1001-1455(2006)02-0115-06
Abstract:
The free-surface velocity profiles of HR2, DT2 and FeMnNi under one-dimensional shock loading were measured by using double-sensitivity VISAR. Combined with the analysis of recovered fragments, dynamic behaviors and spallation phenomena of these materials were studied. Typical triple-wave configurations with phase transition were recorded in DT2 and FeMnNi, but only elastic-plastic double waves were observed in HR2, although the metallographic characters were changed after impact. Multi-spallation and shallow spallation phenomena of DT2 and FeMnNi under homo-thickness target impact were discussed.
The free-surface velocity profiles of HR2, DT2 and FeMnNi under one-dimensional shock loading were measured by using double-sensitivity VISAR. Combined with the analysis of recovered fragments, dynamic behaviors and spallation phenomena of these materials were studied. Typical triple-wave configurations with phase transition were recorded in DT2 and FeMnNi, but only elastic-plastic double waves were observed in HR2, although the metallographic characters were changed after impact. Multi-spallation and shallow spallation phenomena of DT2 and FeMnNi under homo-thickness target impact were discussed.
2006, 26(2): 121-124.
doi: 10.11883/1001-1455(2006)02-0121-04
Abstract:
Tests were performed to investigate the dynamic anomalous response of circular plates impacted by projectiles. Different response modes of the circular plates under different impact velocities have been described. Here exists anomalous response in the narrow velocity ranges. 'Anomalous' here means that the final deflection may be in the direction opposite that of the load. Displacement-history curves of the representative points in the circular plates were experimentally recorded. Experimental results confirm the objectivity of dynamic anomalous behavior and show that this behavior may happen under certain circumstances.
Tests were performed to investigate the dynamic anomalous response of circular plates impacted by projectiles. Different response modes of the circular plates under different impact velocities have been described. Here exists anomalous response in the narrow velocity ranges. 'Anomalous' here means that the final deflection may be in the direction opposite that of the load. Displacement-history curves of the representative points in the circular plates were experimentally recorded. Experimental results confirm the objectivity of dynamic anomalous behavior and show that this behavior may happen under certain circumstances.
2006, 26(2): 125-128.
doi: 10.11883/1001-1455(2006)02-0125-04
Abstract:
A void growth equation is derived for elastic-plastic deformation process by means of representative volume element (RVE). The distribution of the void number density has been numerically investigated under the condition of the same ratio of inner and outer diameters for all voids. Influences of initial damage on development of spalling damage have been indicated by analyzing the distribution of void number density, the cumulative percentage of void volume and the volume fraction of the different-seize voids.
A void growth equation is derived for elastic-plastic deformation process by means of representative volume element (RVE). The distribution of the void number density has been numerically investigated under the condition of the same ratio of inner and outer diameters for all voids. Influences of initial damage on development of spalling damage have been indicated by analyzing the distribution of void number density, the cumulative percentage of void volume and the volume fraction of the different-seize voids.
2006, 26(2): 129-133.
doi: 10.11883/1001-1455(2006)02-0129-05
Abstract:
The high-speed photography was applied to observe the expanding fracture of 45 steel cylinder shells driven by detonation.The clear photos of expanding process of steel cylinder shells were obtained. The fracture strains of the expanding steel shells increase with the strain-rate, and decrease when the strain-rate arrived at a certain constant. The plasticity peak during dynamic fracture was experimentally observed. The strain-rate according to the peak of fracture strain is around 7.1104 s-1.
The high-speed photography was applied to observe the expanding fracture of 45 steel cylinder shells driven by detonation.The clear photos of expanding process of steel cylinder shells were obtained. The fracture strains of the expanding steel shells increase with the strain-rate, and decrease when the strain-rate arrived at a certain constant. The plasticity peak during dynamic fracture was experimentally observed. The strain-rate according to the peak of fracture strain is around 7.1104 s-1.
2006, 26(2): 134-139.
doi: 10.11883/1001-1455(2006)02-0134-06
Abstract:
Interfacial friction effects between specimens and bars in SHPB technique were studied. Five materials with different features,silicon rubber, polyurethane foam, Comp.B explosive, PBX-HMX(97%) polymer bonded explosive and 6061-T6 aluminum alloy,were chosed as specimens. Experimental results show that interfacial friction effects in SHPB tests are related with the tested material properties. Based on the isotropic elastic hypothesis, a theoretic analysis is made on an energy conservation consideration. The reduced theoretic formulations show that material Poisson's ratio, interfacial friction coefficient, length-to-diameter ratio of the specimens and axial strains are four influent factors for the friction effects.
Interfacial friction effects between specimens and bars in SHPB technique were studied. Five materials with different features,silicon rubber, polyurethane foam, Comp.B explosive, PBX-HMX(97%) polymer bonded explosive and 6061-T6 aluminum alloy,were chosed as specimens. Experimental results show that interfacial friction effects in SHPB tests are related with the tested material properties. Based on the isotropic elastic hypothesis, a theoretic analysis is made on an energy conservation consideration. The reduced theoretic formulations show that material Poisson's ratio, interfacial friction coefficient, length-to-diameter ratio of the specimens and axial strains are four influent factors for the friction effects.
2006, 26(2): 140-144.
doi: 10.11883/1001-1455(2006)02-0140-05
Abstract:
A double-sensitivity VISAR was used to measure flyer velocity driven by JB-9014 and JOB-9003 explosives to compare their ability of acceleration. Numerical simulation was performed with the finite element hydrocode DYNA2D. Experimental and calculated results with JO-9159 explosive show that relative kinetic energy of flyer driven by JB-9014 may reach 75.0% of that driven by JOB-9003. Calculated results without JO-9159 explosive show that relative kinetic energy of flyer driven by JB-9014 may reach 71.2% of that driven by JOB-9003.
A double-sensitivity VISAR was used to measure flyer velocity driven by JB-9014 and JOB-9003 explosives to compare their ability of acceleration. Numerical simulation was performed with the finite element hydrocode DYNA2D. Experimental and calculated results with JO-9159 explosive show that relative kinetic energy of flyer driven by JB-9014 may reach 75.0% of that driven by JOB-9003. Calculated results without JO-9159 explosive show that relative kinetic energy of flyer driven by JB-9014 may reach 71.2% of that driven by JOB-9003.
2006, 26(2): 145-149.
doi: 10.11883/1001-1455(2006)02-0145-05
Abstract:
A new-style vibration isolator composed of wire rope isolators and dishing springs was proposed to reconstruct an explosive laboratory's base-isolated system. The relevant base-isolating projects were presented and the assembled isolators were tested. he dynamic responses of the isolated system were nonlinearly analyzed by two-freedom model with damp. The influence of both stiffness and damp of the isolated layer on the dynamical reaction of isolated system was studied. Some parameters of the isolation system were optimized. When the isolating layer's stiffness is about 10 kN/mm and the ratio of damper is 0.20~0.35, results show that the dynamic loads in the isolating layers are the minimum and the other dynamic reactions of the isolating system satisfy the design needs. The anti-shock capability of the reconstructed laboratory increases 50%.
A new-style vibration isolator composed of wire rope isolators and dishing springs was proposed to reconstruct an explosive laboratory's base-isolated system. The relevant base-isolating projects were presented and the assembled isolators were tested. he dynamic responses of the isolated system were nonlinearly analyzed by two-freedom model with damp. The influence of both stiffness and damp of the isolated layer on the dynamical reaction of isolated system was studied. Some parameters of the isolation system were optimized. When the isolating layer's stiffness is about 10 kN/mm and the ratio of damper is 0.20~0.35, results show that the dynamic loads in the isolating layers are the minimum and the other dynamic reactions of the isolating system satisfy the design needs. The anti-shock capability of the reconstructed laboratory increases 50%.
2006, 26(2): 150-155.
doi: 10.11883/1001-1455(2006)02-0150-06
Abstract:
The ballistic impact experiments for composite armor system, which combined with aluminum ahead and FRP behind,were carried out by 7.62 mm caliber uniform firearms. Experimental results and ballistic-resistance mechanism of aluminum target and FRP laminates were analyzed, and the affection of penetration angle and the ballistic-resistance ability for different kinds of reinforced-fiber (including T750, T750/S2 and Spectra900) were discussed. The resistance of aluminum alloy structure with composite armor to small-bore weapon impact was evaluated. Results show that 1.7 T/(100m2) is needed for Dyneema900 FRP and 2.7 T/(100m2) for S/T hybrid FRP to defense 7.62 mm caliber uniform firearms attacking.
The ballistic impact experiments for composite armor system, which combined with aluminum ahead and FRP behind,were carried out by 7.62 mm caliber uniform firearms. Experimental results and ballistic-resistance mechanism of aluminum target and FRP laminates were analyzed, and the affection of penetration angle and the ballistic-resistance ability for different kinds of reinforced-fiber (including T750, T750/S2 and Spectra900) were discussed. The resistance of aluminum alloy structure with composite armor to small-bore weapon impact was evaluated. Results show that 1.7 T/(100m2) is needed for Dyneema900 FRP and 2.7 T/(100m2) for S/T hybrid FRP to defense 7.62 mm caliber uniform firearms attacking.
2006, 26(2): 156-162.
doi: 10.11883/1001-1455(2006)02-0156-07
Abstract:
A compressible fluid-mixture model based on the volume fraction is introduced and a high-order piecewise parabolic method (PPM) is employed to solve the multi-fluid flow which are characterized by the Mie-Grneisen equation of state. The double shock approximation and two level iteration algorithm are used to solve the Riemann problem for general equation of state. A new high resolution scheme is proposed for the mixed type multi-fluid model, which satisfies the principle of oscillation-free for pressure and velocity near the interface between different fluids. For a pure interface problem, the proposed scheme is oscillation-free, and the numerical results also validate that there is no any spurious oscillation in the pressure as well as in velocity profiles on the contact discontinuity while numerical diffusion is limited in two or three cell grids, which is much better than state of the art algorithms. Some numerical experiments and comparisons are presented, and the numerical results show that the new method can simulate the complicated compressible multi-fluid problem such as high pressure ratio Riemann problem, shock-interface interaction and so on.
A compressible fluid-mixture model based on the volume fraction is introduced and a high-order piecewise parabolic method (PPM) is employed to solve the multi-fluid flow which are characterized by the Mie-Grneisen equation of state. The double shock approximation and two level iteration algorithm are used to solve the Riemann problem for general equation of state. A new high resolution scheme is proposed for the mixed type multi-fluid model, which satisfies the principle of oscillation-free for pressure and velocity near the interface between different fluids. For a pure interface problem, the proposed scheme is oscillation-free, and the numerical results also validate that there is no any spurious oscillation in the pressure as well as in velocity profiles on the contact discontinuity while numerical diffusion is limited in two or three cell grids, which is much better than state of the art algorithms. Some numerical experiments and comparisons are presented, and the numerical results show that the new method can simulate the complicated compressible multi-fluid problem such as high pressure ratio Riemann problem, shock-interface interaction and so on.
2006, 26(2): 163-168.
doi: 10.11883/1001-1455(2006)02-0163-06
Abstract:
The elastic-plastic code that can be used to analysize the process of the projectile impacting concrete target with high velocity has been prepared by combination of FEM with SPH algorithm. The sliding surface algorithm with artificial transportation of momentum is proposed. The computational examples show that the penetrating processes with the elastic-plastic projectile analysis are different from that with the rigid projectile analysis. There is a critical velocity especially for the shell warhead and if the impact velocity is over the critical value the warhead will be deformed and damaged seriously, and its penetrating depth can not increase effectively with the increment of the impact velocity. The computations also show that the rate of damage evolving in the damage area of the projectile is related to the impact velocity and it is picked up with the increment of the impact velocity.
The elastic-plastic code that can be used to analysize the process of the projectile impacting concrete target with high velocity has been prepared by combination of FEM with SPH algorithm. The sliding surface algorithm with artificial transportation of momentum is proposed. The computational examples show that the penetrating processes with the elastic-plastic projectile analysis are different from that with the rigid projectile analysis. There is a critical velocity especially for the shell warhead and if the impact velocity is over the critical value the warhead will be deformed and damaged seriously, and its penetrating depth can not increase effectively with the increment of the impact velocity. The computations also show that the rate of damage evolving in the damage area of the projectile is related to the impact velocity and it is picked up with the increment of the impact velocity.
2006, 26(2): 169-173.
doi: 10.11883/1001-1455(2006)02-0169-05
Abstract:
The dynamic compressive experiments were conducted on the open-cell aluminum foams prepared by infiltration process using the SHPB. The dynamic response and strain rate dependence of the aluminum foams with the relative density of 0.341~0.419 were investigated in the strain rate range from 10-3 to 2000 s-1, and the deforming characteristic of the foams was observed by using the scanning electron microscope(SEM). Experimental results show that the flow stresses of the aluminum foams increase with increasing strain rate, demonstrating a distinct strain rate effect in the open-cell aluminum foams. Observed results with SEM reveal a homogeneously macroscopic deforming mode in the dynamic compression of the open-cell aluminum foam. However, the microscopic deformation of the foams is adopted by the transversal stretch of the cells.
The dynamic compressive experiments were conducted on the open-cell aluminum foams prepared by infiltration process using the SHPB. The dynamic response and strain rate dependence of the aluminum foams with the relative density of 0.341~0.419 were investigated in the strain rate range from 10-3 to 2000 s-1, and the deforming characteristic of the foams was observed by using the scanning electron microscope(SEM). Experimental results show that the flow stresses of the aluminum foams increase with increasing strain rate, demonstrating a distinct strain rate effect in the open-cell aluminum foams. Observed results with SEM reveal a homogeneously macroscopic deforming mode in the dynamic compression of the open-cell aluminum foam. However, the microscopic deformation of the foams is adopted by the transversal stretch of the cells.
2006, 26(2): 174-178.
doi: 10.11883/1001-1455(2006)02-0174-05
Abstract:
The shocking-to-detonation transition (SDT) of insensitive high explosives (IHE) including LX-17 and ultrafine TATB was studied by using Hybrid reaction rate model and modified JWL equation of state (EOS), and phenomena of colliding diverging detonation was numerically simulated. The calculated shocking-to-detonation transition (SDT) of insensitive high explosives is in agreement with the experimental result, and the calculated peak pressure in colliding diverging detonation increases 10%.
The shocking-to-detonation transition (SDT) of insensitive high explosives (IHE) including LX-17 and ultrafine TATB was studied by using Hybrid reaction rate model and modified JWL equation of state (EOS), and phenomena of colliding diverging detonation was numerically simulated. The calculated shocking-to-detonation transition (SDT) of insensitive high explosives is in agreement with the experimental result, and the calculated peak pressure in colliding diverging detonation increases 10%.
2006, 26(2): 179-182.
doi: 10.11883/1001-1455(2006)02-0179-04
Abstract:
With an evaluation method based on damage effect on plate and over-pressure impulse criteria, the evaluation experiments of damage power of 3 kinds of FAE warheads are carried out. The TNT equivalent masses of FAE warheads are calculated. The test results indicate that: the deflection of plate subject to 1# FAE becomes larger than that of RDX/TNT with same mass when the distance becomes larger than 3.8m. Between 3.8m and 4.2m, the TNT equivalent mass of 1# FAE is about 2.0. Between 13m and 18m, the deflection of plate subject to 2# FAE is about 1.4 times of 3# FAE, the TNT equivalent masses are 3.75 and 2.96 respectively. The research shows that the damage power can be obtained rapidly with this evaluation method and its experimental method. The results are reliable which can be guidance of evaluation of damage power of FAE warhead.
With an evaluation method based on damage effect on plate and over-pressure impulse criteria, the evaluation experiments of damage power of 3 kinds of FAE warheads are carried out. The TNT equivalent masses of FAE warheads are calculated. The test results indicate that: the deflection of plate subject to 1# FAE becomes larger than that of RDX/TNT with same mass when the distance becomes larger than 3.8m. Between 3.8m and 4.2m, the TNT equivalent mass of 1# FAE is about 2.0. Between 13m and 18m, the deflection of plate subject to 2# FAE is about 1.4 times of 3# FAE, the TNT equivalent masses are 3.75 and 2.96 respectively. The research shows that the damage power can be obtained rapidly with this evaluation method and its experimental method. The results are reliable which can be guidance of evaluation of damage power of FAE warhead.
2006, 26(2): 183-187.
doi: 10.11883/1001-1455(2006)02-0183-05
Abstract:
Numerical simulation has been carried out for blasting demolition of rolling compact concrete cofferdam in crosswise direction of which belongs to the third term of the Three-gorge project using dynamic finite element program LS-DYNA. The influence of corridor and reservoir water on blasting-demolition effect has been numerically analysed. The calculated resultes show that corridor and reservoir water influence forming and extent of blasting notch heavily,which must be considered sufficiently during blasting practice.
Numerical simulation has been carried out for blasting demolition of rolling compact concrete cofferdam in crosswise direction of which belongs to the third term of the Three-gorge project using dynamic finite element program LS-DYNA. The influence of corridor and reservoir water on blasting-demolition effect has been numerically analysed. The calculated resultes show that corridor and reservoir water influence forming and extent of blasting notch heavily,which must be considered sufficiently during blasting practice.
2006, 26(2): 188-192.
doi: 10.11883/1001-1455(2006)02-0188-05
Abstract:
Based on the contact force characteristics in the interface between the free-standing equipment and base, a sliding-kicking up model for free-standing equipment under explosion seism impact is proposed by Matlab/SIMULINK software, and its correctness is verified. The dynamics equations and the critical conditions of different motion states are solved out. The motion process of the free-standing equipment in the real explosion environemnt can be divided into four stages including conglutination, sliding, free flight, hard stops by inputting the real explosion acceleration wave to this model. A reasonable simplified acceleration is developed, and by which variation of the motion response of the free-standing equipment with the kinetic friction coefficient and explosion seism parameters is obtained.
Based on the contact force characteristics in the interface between the free-standing equipment and base, a sliding-kicking up model for free-standing equipment under explosion seism impact is proposed by Matlab/SIMULINK software, and its correctness is verified. The dynamics equations and the critical conditions of different motion states are solved out. The motion process of the free-standing equipment in the real explosion environemnt can be divided into four stages including conglutination, sliding, free flight, hard stops by inputting the real explosion acceleration wave to this model. A reasonable simplified acceleration is developed, and by which variation of the motion response of the free-standing equipment with the kinetic friction coefficient and explosion seism parameters is obtained.
