2005 Vol. 25, No. 3
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2005, 25(3): 193-199.
doi: 10.11883/1001-1455(2005)03-0193-07
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Abstract:
There are many evolution and attenuation mechanisms of stress waves in media, which are mainly controlled by the constitutive factors of the material and the structures geometric factors. Scientific utilization of these mechanisms have important academic and engineering values. In this paper the 2-D numerical simulation code RENEWTO are used to study the attenuation mechanism and the evolution law of stress waves in the concrete material with a cavity. By the method of changing the location and the dimension of the cavity, the attenuation of the intensity and the evolution of the shape of the stress wave behind the cavity are discussed, and the insulation effect of the cavity are analysed too. The results show that the cavity weakens the wave intensity behind it greatly. An approximation formula is presented. This work provides an important basis for designing the scientific intelligent safe protected-layer.
There are many evolution and attenuation mechanisms of stress waves in media, which are mainly controlled by the constitutive factors of the material and the structures geometric factors. Scientific utilization of these mechanisms have important academic and engineering values. In this paper the 2-D numerical simulation code RENEWTO are used to study the attenuation mechanism and the evolution law of stress waves in the concrete material with a cavity. By the method of changing the location and the dimension of the cavity, the attenuation of the intensity and the evolution of the shape of the stress wave behind the cavity are discussed, and the insulation effect of the cavity are analysed too. The results show that the cavity weakens the wave intensity behind it greatly. An approximation formula is presented. This work provides an important basis for designing the scientific intelligent safe protected-layer.
2005, 25(3): 200-206.
doi: 10.11883/1001-1455(2005)03-0200-07
Abstract:
By reckoning the plastic dissipation by membrane force induced by finite deflection, a modifying factor is introduced into the bending-only theory to formulate the governing equations of dynamic plastic response of rectangular plates with deflections where bending moment and membrane force are both important. Based on a kinematically admissible, time-dependent velocity field, a complete theoretical investigation is undertaken to trace the finite deflection response of simply-supported or fully-clamped rigid-plastic rectangular plates to a rectangular pulse or impulsive loading. The present prediction on the final plate deflection agrees well with the corresponding experimental results for deflections up to about 10 times of the plate thickness. This theoretical treatment improves the estimates from the bending-only theory greatly and provides a complete response (including the transient phase) analysis of the rectangular plates, the predictions are much more reliable than the previous mode approximation.
By reckoning the plastic dissipation by membrane force induced by finite deflection, a modifying factor is introduced into the bending-only theory to formulate the governing equations of dynamic plastic response of rectangular plates with deflections where bending moment and membrane force are both important. Based on a kinematically admissible, time-dependent velocity field, a complete theoretical investigation is undertaken to trace the finite deflection response of simply-supported or fully-clamped rigid-plastic rectangular plates to a rectangular pulse or impulsive loading. The present prediction on the final plate deflection agrees well with the corresponding experimental results for deflections up to about 10 times of the plate thickness. This theoretical treatment improves the estimates from the bending-only theory greatly and provides a complete response (including the transient phase) analysis of the rectangular plates, the predictions are much more reliable than the previous mode approximation.
2005, 25(3): 207-216.
doi: 10.11883/1001-1455(2005)03-0207-10
Abstract:
The stress uniformity in split Hopkinson pressure bar (SHPB) test is analyzed in detail by using one-dimensional stress wave theory. The influence of related experimental parameters is evaluated. The advantages and disadvantages of some typical loading waveform are discussed. For brittle material testing, the governing equation of input waveform for attaining constant strain-rate loading is given. The strain-rate limitation of SHPB test under certain stress equilibrium condition is analyzed and some new conclusion is given. The method for experimental data analysis of SHPB for better accuracy is also discussed. A qualitative analysis of uniformity and the wanted loading waveform have been done for testing elastic-plastic material made by diagrammatic method. The result indicates that for elastic-plastic material, the strain uniformity should be considered.
The stress uniformity in split Hopkinson pressure bar (SHPB) test is analyzed in detail by using one-dimensional stress wave theory. The influence of related experimental parameters is evaluated. The advantages and disadvantages of some typical loading waveform are discussed. For brittle material testing, the governing equation of input waveform for attaining constant strain-rate loading is given. The strain-rate limitation of SHPB test under certain stress equilibrium condition is analyzed and some new conclusion is given. The method for experimental data analysis of SHPB for better accuracy is also discussed. A qualitative analysis of uniformity and the wanted loading waveform have been done for testing elastic-plastic material made by diagrammatic method. The result indicates that for elastic-plastic material, the strain uniformity should be considered.
2005, 25(3): 207-221.
doi: 10.11883/1001-1455(2005)03-0217-05
Abstract:
Spectral radiance histories of plasma for He, D2, and H2+D2 gas mixtures with the initial pressure p0=0.6,1.2 MPa after shock compressed by a two-stage light-gas gun was measured by using transient radiation pyrometer. According to the signal amplitude of spectral radiance history, the reflectivity R of LY12 aluminum base-plate surface after shocked was obtained from a typical record by means of fit. It was found that the light reflectivity R (wavelength ranges 340~800 nm) of shocked LY12 aluminum base-plate surface unloading to He, D2 and H2+D2 mixing gas plasma is about 0.4，which decreases to half of the static state reflectivity( ~0.8). The reason of reflectivity decreasing at dynamic loading is discussed.
Spectral radiance histories of plasma for He, D2, and H2+D2 gas mixtures with the initial pressure p0=0.6,1.2 MPa after shock compressed by a two-stage light-gas gun was measured by using transient radiation pyrometer. According to the signal amplitude of spectral radiance history, the reflectivity R of LY12 aluminum base-plate surface after shocked was obtained from a typical record by means of fit. It was found that the light reflectivity R (wavelength ranges 340~800 nm) of shocked LY12 aluminum base-plate surface unloading to He, D2 and H2+D2 mixing gas plasma is about 0.4，which decreases to half of the static state reflectivity( ~0.8). The reason of reflectivity decreasing at dynamic loading is discussed.
2005, 25(3): 222-226.
doi: 10.11883/1001-1455(2005)03-0222-05
Abstract:
By means of high-speed camera and VISAR interferometer, the expanding characteristics of HR-2 steel tube have been investigated under two head-on colliding detonation waves. The images of tube expanding process were obtained successfully by high-speed camera, and the radial displacement data and radial velocity curve of specific position in HR-2 steel tube were obtained too. In addition, we used LSDYNA-3D program to simulate the progress of the steel tube expansion, the results were coincident with the experimental results.
By means of high-speed camera and VISAR interferometer, the expanding characteristics of HR-2 steel tube have been investigated under two head-on colliding detonation waves. The images of tube expanding process were obtained successfully by high-speed camera, and the radial displacement data and radial velocity curve of specific position in HR-2 steel tube were obtained too. In addition, we used LSDYNA-3D program to simulate the progress of the steel tube expansion, the results were coincident with the experimental results.
2005, 25(3): 227-231.
doi: 10.11883/1001-1455(2005)03-0227-05
Abstract:
On the basis of the new ruby laser apparatus, the experiment system of transient holographic interferometry is devised, by which vertical displacement fringe patterns at four different times are acquired in one blasting loading. And the vertical displacement changing of different sections is studied in linear blasting charge. The result shows that the displacements in axis direction are the smallest in any sections; it is found that the phenomenon of end effect which exists in stress field exists in the displacement field in linear charge too. Extreme values of vertical displacement at perpendicular line of the linear charge middle point is the biggest in all of the sections analyzed in the full field after any time of detonation; The strength of the displacement which is caused by Rayleigh wave reduces slowly.
On the basis of the new ruby laser apparatus, the experiment system of transient holographic interferometry is devised, by which vertical displacement fringe patterns at four different times are acquired in one blasting loading. And the vertical displacement changing of different sections is studied in linear blasting charge. The result shows that the displacements in axis direction are the smallest in any sections; it is found that the phenomenon of end effect which exists in stress field exists in the displacement field in linear charge too. Extreme values of vertical displacement at perpendicular line of the linear charge middle point is the biggest in all of the sections analyzed in the full field after any time of detonation; The strength of the displacement which is caused by Rayleigh wave reduces slowly.
2005, 25(3): 232-238.
doi: 10.11883/1001-1455(2005)03-0232-07
Abstract:
The adiabatic decompositions of ammonium nitrate (AN) and non-explosive, irrestorable fertilizer-grade ammonium nitrate (NEIFAN) were investigated by accelerating rate calorimeter (ARC). The experimental data was processed with a dynamic model by means of a computer-control system. The curves of thermal decomposition temperature and pressure versus time, self-heating rate and pressure versus temperature, pseudo zero-order rate constant versus temperature and time to maximum rate versus temperature were obtained. The kinetic parameters such as apparent activation energy, pre-exponential factor, temperature of no return and self-accelerating decomposition temperature were calculated. All of the experimental results indicates that NEIFAN has better thermal stability and safety, and the diminishment or elimination of NEIFAN explosive characteristic is due to the improvement on its thermal stability.
The adiabatic decompositions of ammonium nitrate (AN) and non-explosive, irrestorable fertilizer-grade ammonium nitrate (NEIFAN) were investigated by accelerating rate calorimeter (ARC). The experimental data was processed with a dynamic model by means of a computer-control system. The curves of thermal decomposition temperature and pressure versus time, self-heating rate and pressure versus temperature, pseudo zero-order rate constant versus temperature and time to maximum rate versus temperature were obtained. The kinetic parameters such as apparent activation energy, pre-exponential factor, temperature of no return and self-accelerating decomposition temperature were calculated. All of the experimental results indicates that NEIFAN has better thermal stability and safety, and the diminishment or elimination of NEIFAN explosive characteristic is due to the improvement on its thermal stability.
2005, 25(3): 239-243.
doi: 10.11883/1001-1455(2005)03-0239-05
Abstract:
With two different explosion methods, different super-high pressure components were autofrettaged, one is the dynamic liquid explosion, the other is sticking oily explosion. The super-high pressure component includes thick wall circles with a crack or notch on the inner wall, super-high pressure thick wall cylinders and fours-ways were chosen to conduct autofrettage. The residual stress was measured, and then the fatigue test was carried out. The test results show that the fatigue initiation life Ni can be increased by 5 times, the fatigue progress life Nf can be increased by 8~10 times in the high cycle fatigue period. In the low cycle plastic fatigue period, the fatigue progress life Nf can also be increased by 1 time. The sticking oily explosion is better than the dynamic liquid explosion because of the increasing of the rigidity of the surface.
With two different explosion methods, different super-high pressure components were autofrettaged, one is the dynamic liquid explosion, the other is sticking oily explosion. The super-high pressure component includes thick wall circles with a crack or notch on the inner wall, super-high pressure thick wall cylinders and fours-ways were chosen to conduct autofrettage. The residual stress was measured, and then the fatigue test was carried out. The test results show that the fatigue initiation life Ni can be increased by 5 times, the fatigue progress life Nf can be increased by 8~10 times in the high cycle fatigue period. In the low cycle plastic fatigue period, the fatigue progress life Nf can also be increased by 1 time. The sticking oily explosion is better than the dynamic liquid explosion because of the increasing of the rigidity of the surface.
2005, 25(3): 244-250.
doi: 10.11883/1001-1455(2005)03-0244-07
Abstract:
To explore the plastic flow behaviors of OFHC Cu, the thermomechanical response of OFHC Cu is investigated systematically under quasi-static (Instron, servohydraulic) and dynamic (the split Hopkinson bar) uniaxial compression. Strains over 80% are obtained experimentally, the temperatures are 77 K to 1 000 K, and the strain rates are 0.001 s-1 to 7 000 s-1. Results show that, dynamic strain aging occurs at the temperture of 500 K at a quasi-static strain rate of 0.001 s-1 . With the increase of the strain rates, the temperature region of dynamic strain aging gets higher, even disappears. In the region of higher strains, the flow stress of OFHC Cu is more sensitive to strain rate than to temperature. Based on the concept of dislocation kinematics and kinetics, taking into account the effect of viscous drag on the motion of dislocation, consult the results of a systematical experiment, a physically-based model is developed. This model could be used to predict the flow stress of OFHC Cu over a wide range of temperatures and strain rates. The experimental results are in good agreement with the theoretical predictions.
To explore the plastic flow behaviors of OFHC Cu, the thermomechanical response of OFHC Cu is investigated systematically under quasi-static (Instron, servohydraulic) and dynamic (the split Hopkinson bar) uniaxial compression. Strains over 80% are obtained experimentally, the temperatures are 77 K to 1 000 K, and the strain rates are 0.001 s-1 to 7 000 s-1. Results show that, dynamic strain aging occurs at the temperture of 500 K at a quasi-static strain rate of 0.001 s-1 . With the increase of the strain rates, the temperature region of dynamic strain aging gets higher, even disappears. In the region of higher strains, the flow stress of OFHC Cu is more sensitive to strain rate than to temperature. Based on the concept of dislocation kinematics and kinetics, taking into account the effect of viscous drag on the motion of dislocation, consult the results of a systematical experiment, a physically-based model is developed. This model could be used to predict the flow stress of OFHC Cu over a wide range of temperatures and strain rates. The experimental results are in good agreement with the theoretical predictions.
2005, 25(3): 251-254.
doi: 10.11883/1001-1455(2005)03-0251-04
Abstract:
This paper introduces the performance, applications and existing producing methods of CuCr alloy. The method making powder by mechanical alloying is brought forward. Getting CuCr alloy by explosive sintering and thermal diffusion disposal are studied some primary experiments were done. The results show that CuCr alloy with high density, even structure, thinning crystalloid are obtained. On condition of Cu∶Cr=50∶50, CuCr alloy with nanometer crystalloid, density95% TD, rigidity217HV can be obtained which obviously exceeds the production by hot-isostatic pressing, infiltration and arc melting.
This paper introduces the performance, applications and existing producing methods of CuCr alloy. The method making powder by mechanical alloying is brought forward. Getting CuCr alloy by explosive sintering and thermal diffusion disposal are studied some primary experiments were done. The results show that CuCr alloy with high density, even structure, thinning crystalloid are obtained. On condition of Cu∶Cr=50∶50, CuCr alloy with nanometer crystalloid, density95% TD, rigidity217HV can be obtained which obviously exceeds the production by hot-isostatic pressing, infiltration and arc melting.
2005, 25(3): 255-259.
doi: 10.11883/1001-1455(2005)03-0255-05
Abstract:
Rockmass is a kind of typically complicated structure body with continuous and discontinuous media, and how to simulate the rock failure rule under impact loading is always a hotspot task in numerical simulation research. The Finite Element Method that regards rockmass as a continuous media body, the Discontinuous Element Method and DDA that regards rockmass as a completely discrete body do not either accurately reflects the failure characteristics. The numerical manifold method developed in recent years is a good method, which can simulate the failure behavior of the rockmass. Based on the basic theory of the numerical manifold method, the numerical simulation analysis is made to ascertain the influence of the discontinuous face such as joint, crack and so on on the rock rupture effect. The calculation result shows that numerical manifold method is accurate and effective in simulating this kind of problems.
Rockmass is a kind of typically complicated structure body with continuous and discontinuous media, and how to simulate the rock failure rule under impact loading is always a hotspot task in numerical simulation research. The Finite Element Method that regards rockmass as a continuous media body, the Discontinuous Element Method and DDA that regards rockmass as a completely discrete body do not either accurately reflects the failure characteristics. The numerical manifold method developed in recent years is a good method, which can simulate the failure behavior of the rockmass. Based on the basic theory of the numerical manifold method, the numerical simulation analysis is made to ascertain the influence of the discontinuous face such as joint, crack and so on on the rock rupture effect. The calculation result shows that numerical manifold method is accurate and effective in simulating this kind of problems.
2005, 25(3): 260-264.
doi: 10.11883/1001-1455(2005)03-0260-05
Abstract:
Impact/penetration process is nonlinear dynamic problem with failure. Theories and algorithms related to that process such as nonlinear material constitute model, contact algorithm, material failure pattern etc are formulated. The basic idea and methods for cluster-based parallel finite element method are explored. The application sample illustrate that the proposed equations and parallel idea are effectively to analyze impact/penetration problem.
Impact/penetration process is nonlinear dynamic problem with failure. Theories and algorithms related to that process such as nonlinear material constitute model, contact algorithm, material failure pattern etc are formulated. The basic idea and methods for cluster-based parallel finite element method are explored. The application sample illustrate that the proposed equations and parallel idea are effectively to analyze impact/penetration problem.
2005, 25(3): 265-270.
doi: 10.11883/1001-1455(2005)03-0265-06
Abstract:
Based on the Lagrange finite element method, briefly introduce a computational technique for sliding interface treatment in 3D oblique penetration. The slave elements used in conventional computations are abandoned, and at the same time the slave nodes are advanced. Thereby, the difficulties such as the master-slave element intersection, the sliding interface recognition, modification and redefinition encountered in 3D oblique penetration simulation calculations are avoided to insure high computational precision and efficiency. Numerical computations for the ogive-nosed steel rod penetrating into the aluminum target show that the computational results are in good agreement with the experimental results for both normal and oblique penetrations. Therefore, the method discussed and the program developed are reasonable and effective, and they are resultful for the numerical study on penetration and perforation.
Based on the Lagrange finite element method, briefly introduce a computational technique for sliding interface treatment in 3D oblique penetration. The slave elements used in conventional computations are abandoned, and at the same time the slave nodes are advanced. Thereby, the difficulties such as the master-slave element intersection, the sliding interface recognition, modification and redefinition encountered in 3D oblique penetration simulation calculations are avoided to insure high computational precision and efficiency. Numerical computations for the ogive-nosed steel rod penetrating into the aluminum target show that the computational results are in good agreement with the experimental results for both normal and oblique penetrations. Therefore, the method discussed and the program developed are reasonable and effective, and they are resultful for the numerical study on penetration and perforation.
2005, 25(3): 271-275.
doi: 10.11883/1001-1455(2005)03-0271-05
Abstract:
The formation of metallic nanooxides via detonation reaction was investigated with respect to the presence of an energetic precursor, such as the metallic nitrate and the degree of confinement of the explosive charge. The detonation products were characterized by scanning electron microscopy. Nano-metallic oxides with diameters from 10 to 50 nm and a variety of morphologies were found. Carbon particles in the oxides, the grey detonation soot, indicate a catalytic growth mechanism in a sense. The detonation synthesis technique is one of the methods of producing nano-metallic oxides. The oxides produced by this cheap method affirmed the validity of detonation synthesis of nano-size powders. The paper is concerned with the fabrication of alumina. The microstructure, distributions of the Al2O3 were determined. The results show that the nano-metallic oxides produced by detonation of nitrate explosives are between 20 to 50 nm. This investigation also promotes the design of commercial explosives and the development of detonation theory on a microscale.
The formation of metallic nanooxides via detonation reaction was investigated with respect to the presence of an energetic precursor, such as the metallic nitrate and the degree of confinement of the explosive charge. The detonation products were characterized by scanning electron microscopy. Nano-metallic oxides with diameters from 10 to 50 nm and a variety of morphologies were found. Carbon particles in the oxides, the grey detonation soot, indicate a catalytic growth mechanism in a sense. The detonation synthesis technique is one of the methods of producing nano-metallic oxides. The oxides produced by this cheap method affirmed the validity of detonation synthesis of nano-size powders. The paper is concerned with the fabrication of alumina. The microstructure, distributions of the Al2O3 were determined. The results show that the nano-metallic oxides produced by detonation of nitrate explosives are between 20 to 50 nm. This investigation also promotes the design of commercial explosives and the development of detonation theory on a microscale.
2005, 25(3): 276-280.
doi: 10.11883/1001-1455(2005)03-0276-05
Abstract:
In order to simulate the ground shock and vibration under nuclear explosion and conventional weapon blast, according to the principles of energy conservation and elastic colliding, a hanging test table which is used to simulate blast shock and vibration is manufactured. The table can provide shock and vibration in horizontal and vertical direction. By adjusted the parameters, such as the height and weight of the hammer and cushion thickness, the table can achieve the following parameters: the horizontal peak acceleration is 5-1 500 m/s2, the action time is 50-4 ms; the vertical peak acceleration is 5-1 000 m/s2, the action time is 60-4 ms. The experiment result indicates that the table meets the design requests, which provides a safety, convenient, economical, reliable trial means.
In order to simulate the ground shock and vibration under nuclear explosion and conventional weapon blast, according to the principles of energy conservation and elastic colliding, a hanging test table which is used to simulate blast shock and vibration is manufactured. The table can provide shock and vibration in horizontal and vertical direction. By adjusted the parameters, such as the height and weight of the hammer and cushion thickness, the table can achieve the following parameters: the horizontal peak acceleration is 5-1 500 m/s2, the action time is 50-4 ms; the vertical peak acceleration is 5-1 000 m/s2, the action time is 60-4 ms. The experiment result indicates that the table meets the design requests, which provides a safety, convenient, economical, reliable trial means.
2005, 25(3): 281-284.
doi: 10.11883/1001-1455(2005)03-0281-04
Abstract:
The growth of pore pressure of clay under shock load infuence effective stress and strength of clay directly. Numerical analysis on the growth principles of pore pressure of clay under shock load provides theoretical references for dynamic responses analysis of clay and dynamic consolidation of clay medium. The transient shock load has been simplified into trial anger load and the transient dynamic elastic plastic finite element program has been programed. The dynamic responses of pore pressure of clay under shock load has been simulated. Some growth principles of pore pressure of clay under shock load have been concluded.The peak pore pressure attenuates exponentially with the increase of the horizontal distance and the augmentation of the depth. Calculation and analyses are in good agreement with monitoring datas of practical engineering case.
The growth of pore pressure of clay under shock load infuence effective stress and strength of clay directly. Numerical analysis on the growth principles of pore pressure of clay under shock load provides theoretical references for dynamic responses analysis of clay and dynamic consolidation of clay medium. The transient shock load has been simplified into trial anger load and the transient dynamic elastic plastic finite element program has been programed. The dynamic responses of pore pressure of clay under shock load has been simulated. Some growth principles of pore pressure of clay under shock load have been concluded.The peak pore pressure attenuates exponentially with the increase of the horizontal distance and the augmentation of the depth. Calculation and analyses are in good agreement with monitoring datas of practical engineering case.
2005, 25(3): 285-288.
doi: 10.11883/1001-1455(2005)03-0285-04
Abstract:
The characterization of slow cook-off is a primary parameter for evaluating insensitive munitions. Use the apparatus of cook-off test manufactured by ourselves, the effects of the explosive charging sizes on the response characterization of the slow cook-off were studied by experiments three explosives JB-B, TNT and R852 were chosen. The results show that with charging sizes extending, the reaction environmental temperature and the reaction violence increase, the reasons are discussed and analyzed.
The characterization of slow cook-off is a primary parameter for evaluating insensitive munitions. Use the apparatus of cook-off test manufactured by ourselves, the effects of the explosive charging sizes on the response characterization of the slow cook-off were studied by experiments three explosives JB-B, TNT and R852 were chosen. The results show that with charging sizes extending, the reaction environmental temperature and the reaction violence increase, the reasons are discussed and analyzed.
