2006 Vol. 26, No. 6
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2006, 26(6): 481-485.
doi: 10.11883/1001-1455(2006)06-0481-05
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Abstract:
The dynamic tension experimental technique of electromagnetically driven thin metal rings expansion was described, and quick-discharge switch and cut-off switch were improved to achieve rings free expansion. The approach is useful for studies on material constitutive relationship, dynamic fracture and fragmentation. The main circuit current was measured by Rogowski probe, and the expansion velocity was obtained from slit scanning cameras displacement measurement. The flow stress, strain, strain rate, expansion velocity and temperature rise of ring was obtained by electrodynamics analysis calculation.
The dynamic tension experimental technique of electromagnetically driven thin metal rings expansion was described, and quick-discharge switch and cut-off switch were improved to achieve rings free expansion. The approach is useful for studies on material constitutive relationship, dynamic fracture and fragmentation. The main circuit current was measured by Rogowski probe, and the expansion velocity was obtained from slit scanning cameras displacement measurement. The flow stress, strain, strain rate, expansion velocity and temperature rise of ring was obtained by electrodynamics analysis calculation.
2006, 26(6): 486-491.
doi: 10.11883/1001-1455(2006)06-0486-06
Abstract:
Reverse-impact method used to measure the high-pressure sound velocity in shock-compressed metals was described. Two reverse-impact set-ups, Ta/LY12 Al buffer/LiF window and Ta/LiF window, were used to measure the sound velocity in shock-compressed Ta over the range of 110~131 GPa . Measured longitudinal sound velocities in Ta are consistent with the data reported by Brown J M, et al. No significant effects of LY12 Al buffer on the measurement uncertainty of sound velocity were found because of little difference in impedance between LY12 Al and LiF. The longitudinal sound velocities of LY12 Al buffer were determined at 110 GPa and 131 GPa. The data combining with those reported by McQueen R G show that the longitudinal sound velocities in LY12 Al decrease gradually to bulk sound velocities with pressure over the range of 125~150 GPa.
Reverse-impact method used to measure the high-pressure sound velocity in shock-compressed metals was described. Two reverse-impact set-ups, Ta/LY12 Al buffer/LiF window and Ta/LiF window, were used to measure the sound velocity in shock-compressed Ta over the range of 110~131 GPa . Measured longitudinal sound velocities in Ta are consistent with the data reported by Brown J M, et al. No significant effects of LY12 Al buffer on the measurement uncertainty of sound velocity were found because of little difference in impedance between LY12 Al and LiF. The longitudinal sound velocities of LY12 Al buffer were determined at 110 GPa and 131 GPa. The data combining with those reported by McQueen R G show that the longitudinal sound velocities in LY12 Al decrease gradually to bulk sound velocities with pressure over the range of 125~150 GPa.
2006, 26(6): 492-497.
doi: 10.11883/1001-1455(2006)06-0492-06
Abstract:
By using the nonlinear ZWT model and the genetic algorithm method and taking the rate-dependent effects and damage evolution into account, experiments in the quasi-static and impact loading were performed to study the visco-elastic mechanical behaviors of PP/PA polymer blends with two types of interface modifier in the large deformation condition. The nonlinear visco-elastic constitutive equations considering damage evolution for these materials were obtained respectively. Results show that the deformation mechanisms of polymer blends with two different compatibilizers in the large deformation condition are different due to the visco-plastic effect, and that the visco-plastic deformation influences the polymer blend with TPE-g as compatilizer more greatly than the polymer blend with PP-g-MAH as compatilizer, and the strain range, in which the ZWT model can be applicable, is 15% for the former, while for the latter it is 24%.
By using the nonlinear ZWT model and the genetic algorithm method and taking the rate-dependent effects and damage evolution into account, experiments in the quasi-static and impact loading were performed to study the visco-elastic mechanical behaviors of PP/PA polymer blends with two types of interface modifier in the large deformation condition. The nonlinear visco-elastic constitutive equations considering damage evolution for these materials were obtained respectively. Results show that the deformation mechanisms of polymer blends with two different compatibilizers in the large deformation condition are different due to the visco-plastic effect, and that the visco-plastic deformation influences the polymer blend with TPE-g as compatilizer more greatly than the polymer blend with PP-g-MAH as compatilizer, and the strain range, in which the ZWT model can be applicable, is 15% for the former, while for the latter it is 24%.
2006, 26(6): 498-504.
doi: 10.11883/1001-1455(2006)06-0498-07
Abstract:
A new method was developed to analyze the Taylor impact problem of the rigid target vertically impacted by a cylinder projectile. The quadric nonlinear velocity variation was proposed in this method for the part of a projectile that has not any deformation occurring during the impact process. An analytic formula for the Taylor impact was deduced from motion equations of projectiles, and the new meshless method, reproducing kernel particle method was applied to numerically simulate the Taylor impact. Theoretical analysis on the Taylor impact of five practical materials shows that the analytic results are in agreement with the experimental and numerical.
A new method was developed to analyze the Taylor impact problem of the rigid target vertically impacted by a cylinder projectile. The quadric nonlinear velocity variation was proposed in this method for the part of a projectile that has not any deformation occurring during the impact process. An analytic formula for the Taylor impact was deduced from motion equations of projectiles, and the new meshless method, reproducing kernel particle method was applied to numerically simulate the Taylor impact. Theoretical analysis on the Taylor impact of five practical materials shows that the analytic results are in agreement with the experimental and numerical.
2006, 26(6): 505-509.
doi: 10.11883/1001-1455(2006)06-0505-05
Abstract:
The-depth-of-penetration (DOP) experiment of explosively-formed projectile (EFP) penetrating Al2O3 armor ceramic was performed, and the mass protection and difference protection coefficients and the variety of them along with the ceramic thickness were gained. The capability of 99Al2O3 armor ceramic resisting EFP penetration was evaluated，and the process and mechanisms of armor ceramic resisting EFP penetration was explained. Researched results show that the capability of ceramic resisting penetration can be improved by adding restriction.
The-depth-of-penetration (DOP) experiment of explosively-formed projectile (EFP) penetrating Al2O3 armor ceramic was performed, and the mass protection and difference protection coefficients and the variety of them along with the ceramic thickness were gained. The capability of 99Al2O3 armor ceramic resisting EFP penetration was evaluated，and the process and mechanisms of armor ceramic resisting EFP penetration was explained. Researched results show that the capability of ceramic resisting penetration can be improved by adding restriction.
2006, 26(6): 510-515.
doi: 10.11883/1001-1455(2006)06-0510-06
Abstract:
By means of optical fibre probe, optical-electrical converter, and oscillograph diagnostic technique, the run distance to detonation was measured as a function of initial shock pressure in a TATB/HMX-based explosive. High amplitude and short duration shock stimuli generated by an electric gun were used to initiate the cylindrical wedges of explosive material. The experimental technique was described, and the results in the form of POP plots for the TATB/HMX-based formulation were presented. These experimental data may give some insight into the effect of pulse duration on the initiation and growth to detonation characteristics in insensitive high explosives. For the short-duration shock loading, the effect of the pulse duration on the run distance to detonation of explosive is obvious. Under the same experimental conditions, the longer the pulse duration , the shorter the run distance to detonation. And for the same pulse duration, the higher the loading pressure, the shorter the run distance to detonation.
By means of optical fibre probe, optical-electrical converter, and oscillograph diagnostic technique, the run distance to detonation was measured as a function of initial shock pressure in a TATB/HMX-based explosive. High amplitude and short duration shock stimuli generated by an electric gun were used to initiate the cylindrical wedges of explosive material. The experimental technique was described, and the results in the form of POP plots for the TATB/HMX-based formulation were presented. These experimental data may give some insight into the effect of pulse duration on the initiation and growth to detonation characteristics in insensitive high explosives. For the short-duration shock loading, the effect of the pulse duration on the run distance to detonation of explosive is obvious. Under the same experimental conditions, the longer the pulse duration , the shorter the run distance to detonation. And for the same pulse duration, the higher the loading pressure, the shorter the run distance to detonation.
2006, 26(6): 516-521.
doi: 10.11883/1001-1455(2006)06-0516-06
Abstract:
The experiment and data reduction techniques were improved in the self-consistent method (so called AC method). One-stepped sample and single-flyer instead of the usual two-stepped sample and two-layer combined flyer were used in loading-unloading experiments. This experimental configuration can meet the physical requirements and simplify the wave interaction of loading-unloading process. The location of elastic-plastic transition is more accurately identified based on the acquired Lagrangian sound velocity against particle velocity, relative to based on the Lagrangian sound velocity against engineering strain. The dynamic yield strength of LY12-aluminum treated by low temperature annealing at 20.0 GPa shock stress was measured by using the improved AC method. The results obtained by integral method and graphical method are consistent.
The experiment and data reduction techniques were improved in the self-consistent method (so called AC method). One-stepped sample and single-flyer instead of the usual two-stepped sample and two-layer combined flyer were used in loading-unloading experiments. This experimental configuration can meet the physical requirements and simplify the wave interaction of loading-unloading process. The location of elastic-plastic transition is more accurately identified based on the acquired Lagrangian sound velocity against particle velocity, relative to based on the Lagrangian sound velocity against engineering strain. The dynamic yield strength of LY12-aluminum treated by low temperature annealing at 20.0 GPa shock stress was measured by using the improved AC method. The results obtained by integral method and graphical method are consistent.
2006, 26(6): 522-527.
doi: 10.11883/1001-1455(2006)06-0522-06
Abstract:
By solving two-dimensional axisymmetric Navier-Stokes equations in conjunction with the chemistry, a numerical simulation of pulse detonation process induced by flame in the tube with CH4-O2-N2 mixture and the flow field outside was performed, and a detailed chemical mechanism of CH4-O2-N2 system, which included 14 species and 19 element reactions, was involved. The computational results demonstrate the process of the development, steady propagation, degenerating into a shock after the detonation wave went into the flow field outside and complex vortex /shock interactions in the vicinity of the thruster exit. The pressure distribution of axis and the head-end (thrust wall) thrust history were discussed to research and exploit a pulse detonation engine .
By solving two-dimensional axisymmetric Navier-Stokes equations in conjunction with the chemistry, a numerical simulation of pulse detonation process induced by flame in the tube with CH4-O2-N2 mixture and the flow field outside was performed, and a detailed chemical mechanism of CH4-O2-N2 system, which included 14 species and 19 element reactions, was involved. The computational results demonstrate the process of the development, steady propagation, degenerating into a shock after the detonation wave went into the flow field outside and complex vortex /shock interactions in the vicinity of the thruster exit. The pressure distribution of axis and the head-end (thrust wall) thrust history were discussed to research and exploit a pulse detonation engine .
2006, 26(6): 528-531.
doi: 10.11883/1001-1455(2006)06-0528-04
Abstract:
The thermal decomposition process of 1,1-diamino-2,2-dinitroethylene (FOX-7) was investigated by differential scaning calorimety(DSC), thermogravimety(TG) and T-Jump rapid scan-FTIR coupling techniques. Results show that the isomerization of the -NO2 group occurs and NO is released ,and then the decomposition of main framework of FOX-7 liberates HNCO, HCN, NH3, CO2, CO, etc. The activation energy Ea is 246.65 kJ/mol,the factor in front of exponential lgA is 23.81.The pyrolysis mechanism of early stage of FOX-7 is the reaction of nuclear formation and development, and its reaction order is 1.5.
The thermal decomposition process of 1,1-diamino-2,2-dinitroethylene (FOX-7) was investigated by differential scaning calorimety(DSC), thermogravimety(TG) and T-Jump rapid scan-FTIR coupling techniques. Results show that the isomerization of the -NO2 group occurs and NO is released ,and then the decomposition of main framework of FOX-7 liberates HNCO, HCN, NH3, CO2, CO, etc. The activation energy Ea is 246.65 kJ/mol,the factor in front of exponential lgA is 23.81.The pyrolysis mechanism of early stage of FOX-7 is the reaction of nuclear formation and development, and its reaction order is 1.5.
2006, 26(6): 532-536.
doi: 10.11883/1001-1445(2006)06-0532-05
Abstract:
The planar spall experiments for OFHC were performed on the gas gun facility. 6 mm thickness OFHC sample with PMMA buffer was mounted in a stationary target holder and impacted by 3 mm thickness OFHC flyer carried within the head of the projectile body. The stress history at the interface between the OFHC sample and PMMA was measured by using manganin gage and the OFHC sample was recovered for post-test evolution. A void coalescence-based spall model proposed by Chen et al was used to simulate these experiments numerically. The computed results were compared with the stress recorded by manganin gage and the observed spall plane in recovered samples. The planar spall experiments for OFHC performed by Curran et al were simulated numerically by using the void coalescence-based spall model.
2006, 26(6): 537-542.
doi: 10.11883/1001-1455(2006)06-0537-06
Abstract:
A polymeric buffer bar is employed to replace the conventional metallic transmission bar in a split Hopkinson pressure bar to determine the spalling strength of a long concrete rod that is placed between the metallic incident bar and the polymer buffer bar. Since the polymer bar material has a lower mechanical impedance than the concrete specimen, spalling can be produced in the concrete rod after the compressive wave in the concrete specimen is reflected back as a tension wave at the concrete/buffer bar interface. The spalling in the concrete is detected by examining the profile of the transmitted pulse in the buffer bar. Even though the profile of the transmitted pulse recorded by the strain gages on the buffer bar may vary due to wave dispersion in such a viscoelastic buffer bar, a 3-D finite element analysis indicates that the wave dispersion correction is not necessary when the transmitted pulse is used to determine the spalling strength of the concrete specimen. The spalling strength is determined by using the records from the strain gages on the buffer bar on the basis of classic 1-D theory of characteristics.
A polymeric buffer bar is employed to replace the conventional metallic transmission bar in a split Hopkinson pressure bar to determine the spalling strength of a long concrete rod that is placed between the metallic incident bar and the polymer buffer bar. Since the polymer bar material has a lower mechanical impedance than the concrete specimen, spalling can be produced in the concrete rod after the compressive wave in the concrete specimen is reflected back as a tension wave at the concrete/buffer bar interface. The spalling in the concrete is detected by examining the profile of the transmitted pulse in the buffer bar. Even though the profile of the transmitted pulse recorded by the strain gages on the buffer bar may vary due to wave dispersion in such a viscoelastic buffer bar, a 3-D finite element analysis indicates that the wave dispersion correction is not necessary when the transmitted pulse is used to determine the spalling strength of the concrete specimen. The spalling strength is determined by using the records from the strain gages on the buffer bar on the basis of classic 1-D theory of characteristics.
2006, 26(6): 543-549.
doi: 10.11883/1001-1455(2006)06-0543-07
Abstract:
Detonation characteristics of several fuel vapor (propylene epoxide, IPN,C5~C6, hexane, heptane, decane)-air mixtures were studied. Critical initiation energy was measured by the up-and-down method and cell size on soot foil. Results demonstrate that the relationship of critical initiation energy and equivalence ratio shows a U-shaped curve, the critical energy is obtained when equivalence ratio is slightly larger than 1. Meanwhile these results are used to calculate theoretical critical initiation energy of hydrocarbon-air mixture in unconfined conditions, and calculated values agree well with experimental results. The comparison of detonation characteristics among these fuels indicates that detonation of FAE in low fuel vapor pressure is similar to the gaseous detonation. These experimental results enable us to have an insight into the detonation nature of fuel-air mixtures.
Detonation characteristics of several fuel vapor (propylene epoxide, IPN,C5~C6, hexane, heptane, decane)-air mixtures were studied. Critical initiation energy was measured by the up-and-down method and cell size on soot foil. Results demonstrate that the relationship of critical initiation energy and equivalence ratio shows a U-shaped curve, the critical energy is obtained when equivalence ratio is slightly larger than 1. Meanwhile these results are used to calculate theoretical critical initiation energy of hydrocarbon-air mixture in unconfined conditions, and calculated values agree well with experimental results. The comparison of detonation characteristics among these fuels indicates that detonation of FAE in low fuel vapor pressure is similar to the gaseous detonation. These experimental results enable us to have an insight into the detonation nature of fuel-air mixtures.
2006, 26(6): 550-555.
doi: 10.11883/1001-1455(2006)06-0550-06
Abstract:
By using a Roe scheme of 2nd-order space accuracy and a MUSCLE approach, the propagation of laser-induced shock wave and the thrust generating process of axisymmetric laser thruster were simulated numerically under the air model of perfect gas and high-temperature equilibrium gas to explore the thrust generating mechanism of air-breathing laser propulsion. The result indicates that high-temperature equilibrium gas model can give a more accurate result than perfect gas model.
By using a Roe scheme of 2nd-order space accuracy and a MUSCLE approach, the propagation of laser-induced shock wave and the thrust generating process of axisymmetric laser thruster were simulated numerically under the air model of perfect gas and high-temperature equilibrium gas to explore the thrust generating mechanism of air-breathing laser propulsion. The result indicates that high-temperature equilibrium gas model can give a more accurate result than perfect gas model.
2006, 26(6): 556-561.
doi: 10.11883/1001-1455(2006)06-0556-06
Abstract:
Numerical investigations were carried out to study the phenomena of detonation sweeping a contact surface of inert gas and its decoupling. The control-equations were solved with upwind TVD algorithm and elemental chemical reaction model, with the point-implicit used to overcome the numerical stiffness of chemical reaction source term. The results show that, when detonation sweeps a contact surface of inert gas, interactions of detonation, transmit shock and contact surface take place; in condition of high N2 dilution proportion, detonation is decoupled by rarefaction waves.
Numerical investigations were carried out to study the phenomena of detonation sweeping a contact surface of inert gas and its decoupling. The control-equations were solved with upwind TVD algorithm and elemental chemical reaction model, with the point-implicit used to overcome the numerical stiffness of chemical reaction source term. The results show that, when detonation sweeps a contact surface of inert gas, interactions of detonation, transmit shock and contact surface take place; in condition of high N2 dilution proportion, detonation is decoupled by rarefaction waves.
2006, 26(6): 562-567.
doi: 10.11883/1001-1455(2006)06-0562-06
Abstract:
The anti-blasting and absorbing energy mechanisms of composite protective structure under blasting loads were numerically simulated by applying ANSYS/LS-DYNA. The energy distribution regulation shows that the foam concrete has greater effects of the reflection and absorbing energy, and changes the energy distribution in the protective structure. The more energy is absorbed by top layers，the energy in the bottom layer is only 14% of that in the structure without absorbing energy layer.
The anti-blasting and absorbing energy mechanisms of composite protective structure under blasting loads were numerically simulated by applying ANSYS/LS-DYNA. The energy distribution regulation shows that the foam concrete has greater effects of the reflection and absorbing energy, and changes the energy distribution in the protective structure. The more energy is absorbed by top layers，the energy in the bottom layer is only 14% of that in the structure without absorbing energy layer.
2006, 26(6): 568-571.
doi: 10.11883/1001-1455(2006)06-0568-04
Abstract:
With an equipment using Hopkinson pressure bar technique, and using a quartz gage pressure sensors，the high shock acceleration sensors were calibrated, and the calculating formula of the accelerometer sensitivity was developed. The experimental results show that the equipment designed to calibrate high shock acceleration sensors using a quartz gage pressure sensors can meet the calibration precision prescribed completely, and the whole calibration system has the advantage of simple structure, ease in library construction.
With an equipment using Hopkinson pressure bar technique, and using a quartz gage pressure sensors，the high shock acceleration sensors were calibrated, and the calculating formula of the accelerometer sensitivity was developed. The experimental results show that the equipment designed to calibrate high shock acceleration sensors using a quartz gage pressure sensors can meet the calibration precision prescribed completely, and the whole calibration system has the advantage of simple structure, ease in library construction.
2006, 26(6): 572-576.
doi: 10.11883/1001-1455(2006)06-0572-05
Abstract:
TVD format and elementary reaction model are applied to the study of numerical simulation for phenomena of chemical non-equilibrium oblique detonation wave standing on a projectile. A parallel arithmetic based on MPI parallel environment on PC-Cluster system for the oblique detonation wave flow field is discussed. The results of parallel computation indicate that the parallel computation is practical and efficient for simulating the standing oblique detonation waves.
TVD format and elementary reaction model are applied to the study of numerical simulation for phenomena of chemical non-equilibrium oblique detonation wave standing on a projectile. A parallel arithmetic based on MPI parallel environment on PC-Cluster system for the oblique detonation wave flow field is discussed. The results of parallel computation indicate that the parallel computation is practical and efficient for simulating the standing oblique detonation waves.
