2005 Vol. 25, No. 4
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2005, 25(4): 289-295.
doi: 10.11883/1001-1455(2005)04-0289-07
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Abstract:
Actions of hoop steel-bar, portrait steel-bar, and steel plate on perforation block in RCBSP are discussed. According to the deformation and failure of RCBSP and distribution of energy in time and space, deformation and failure models of RCBSP are established. In addition, resistance formulae of hoop reinforcing steel bar and steel plate to projectile are deduced, and by regarding the reinforcing steel bar net as an equivalent steel plate, the motion equations of projectile and perforation block are proposed. The acceleration, speed, and displacement of projectile in concrete are compared with those in BCBSP, showing the influence of the elements in RCBSP on projectile's displacement field.
Actions of hoop steel-bar, portrait steel-bar, and steel plate on perforation block in RCBSP are discussed. According to the deformation and failure of RCBSP and distribution of energy in time and space, deformation and failure models of RCBSP are established. In addition, resistance formulae of hoop reinforcing steel bar and steel plate to projectile are deduced, and by regarding the reinforcing steel bar net as an equivalent steel plate, the motion equations of projectile and perforation block are proposed. The acceleration, speed, and displacement of projectile in concrete are compared with those in BCBSP, showing the influence of the elements in RCBSP on projectile's displacement field.
2005, 25(4): 296-302.
doi: 10.11883/1001-1455(2005)04-0296-07
Abstract:
Within the framework of continuum mechanics and immiscible mixture theory, and by assuming that there is no relative motion between the components, an elastic-plastic constitutive model involving damage evolution for fluid-saturated porous solid is proposed. The porosity evolution is established on the conventional equipressure experiments and the effect of porosity on the yield function is considered in the new constitutive relations. By using the B-W-N-B effective stress rule, the blast waves in the fully water-saturated porous tuff are numerically simulated and the results are in good agreement with experiments, demonstrating that the model proposed in this paper is capable of predicting blast waves in water-saturated porous rocks.
Within the framework of continuum mechanics and immiscible mixture theory, and by assuming that there is no relative motion between the components, an elastic-plastic constitutive model involving damage evolution for fluid-saturated porous solid is proposed. The porosity evolution is established on the conventional equipressure experiments and the effect of porosity on the yield function is considered in the new constitutive relations. By using the B-W-N-B effective stress rule, the blast waves in the fully water-saturated porous tuff are numerically simulated and the results are in good agreement with experiments, demonstrating that the model proposed in this paper is capable of predicting blast waves in water-saturated porous rocks.
2005, 25(4): 303-308.
doi: 10.11883/1001-1455(2005)04-0303-06
Abstract:
Experiments were performed to investigate the magnetically accelerating flyers using fast pulsed power. Two flyers with different thicknesses were launched simultaneously, and their velocity histories were recorded by VISAR. When the maximum current density was 823 kA/cm, the flyer 0.38 mm in thickness and 4 mm in diameter could be accelerated to the velocity of 1.5 km/s in 2 s, and its maximum magnetic loading pressure was 4.25 GPa. It was observed from the metallographs that when flyer velocity was high, there was amorphous body on the shear fracture zone at the bottom of the counterbore left by the flyer due to large degree of supercooling in freezing. This work will be helpful to further development of isentropic compression technique and the study of equation of state.
Experiments were performed to investigate the magnetically accelerating flyers using fast pulsed power. Two flyers with different thicknesses were launched simultaneously, and their velocity histories were recorded by VISAR. When the maximum current density was 823 kA/cm, the flyer 0.38 mm in thickness and 4 mm in diameter could be accelerated to the velocity of 1.5 km/s in 2 s, and its maximum magnetic loading pressure was 4.25 GPa. It was observed from the metallographs that when flyer velocity was high, there was amorphous body on the shear fracture zone at the bottom of the counterbore left by the flyer due to large degree of supercooling in freezing. This work will be helpful to further development of isentropic compression technique and the study of equation of state.
2005, 25(4): 309-312.
doi: 10.11883/1001-1455(2005)04-0309-04
Abstract:
A simplified model of nonideal detonation energy release is proposed to account for the effect of nonideal detonation on underwater explosion. Based on the CJ detonation theory and the later reaction theory, the model divides chemical reactions in aluminized explosives into fast and slow reactions, and takes the released chemical energy and the slow reaction rate as the nonideal characteristic parameters. One-dimensional calculations using this model are in good agreement with the experiments, with the error in peak pressure of shock wave and the error in decay time constant less than 10% and 5%, respectively. The shock wave energies are also in agreement with the experimental results. This indicates that this simplified model has correctly described the major processes and characteristics of the nonideal detonation, and can be used in explosive design and explosion effect analysis.
A simplified model of nonideal detonation energy release is proposed to account for the effect of nonideal detonation on underwater explosion. Based on the CJ detonation theory and the later reaction theory, the model divides chemical reactions in aluminized explosives into fast and slow reactions, and takes the released chemical energy and the slow reaction rate as the nonideal characteristic parameters. One-dimensional calculations using this model are in good agreement with the experiments, with the error in peak pressure of shock wave and the error in decay time constant less than 10% and 5%, respectively. The shock wave energies are also in agreement with the experimental results. This indicates that this simplified model has correctly described the major processes and characteristics of the nonideal detonation, and can be used in explosive design and explosion effect analysis.
2005, 25(4): 313-318.
doi: 10.11883/1001-1455(2005)04-0313-06
Abstract:
Formation process and the three fins of the over-turned EFP ignited at three points are numerically simulated with LS-DYNA3D finite element code. Simulated results are in good agreement with experiments, providing the important reference for improvement and optimization of EFP design. Two constitutive models, Johnson-Cook and Steinberg, have been used to model the liner material. The results show that the constitutive model has some effect on the shape of the fins and the Steinberg model appears better in reproducing the experimental results.
Formation process and the three fins of the over-turned EFP ignited at three points are numerically simulated with LS-DYNA3D finite element code. Simulated results are in good agreement with experiments, providing the important reference for improvement and optimization of EFP design. Two constitutive models, Johnson-Cook and Steinberg, have been used to model the liner material. The results show that the constitutive model has some effect on the shape of the fins and the Steinberg model appears better in reproducing the experimental results.
2005, 25(4): 319-324.
doi: 10.11883/1001-1455(2005)04-0319-06
Abstract:
By accounting for the effects of temperature and damage on material parameters and the coupled effects of temperature and damage on the plastic deformation, a general explicit form and a specific incremental form of a thermal-plastic constitutive relation have been obtained based on the internal variable theory. For the problem of imploding load induced spallation in spherical shell, a set of equations have been developed and numerically solved with finite difference method.
By accounting for the effects of temperature and damage on material parameters and the coupled effects of temperature and damage on the plastic deformation, a general explicit form and a specific incremental form of a thermal-plastic constitutive relation have been obtained based on the internal variable theory. For the problem of imploding load induced spallation in spherical shell, a set of equations have been developed and numerically solved with finite difference method.
2005, 25(4): 325-329.
doi: 10.11883/1001-1455(2005)04-0325-05
Abstract:
The equilibrium compositions of detonation products of PETN, RDX and HMX explosives are calculated by solving chemical equilibrium equations based on minimizing Gibbs free energy. The results are in good agreement with the results obtained based on BKW and LJD equations of state. The Gibbs free energy of carbon is calculated based on the most probable state of dissociated carbon in detonation products, which is determined by distinguishing the following four states of carbon: graphite, diamond, graphitelike and diamondlike.The WCA equation is taken as the equation of state of detonation products, and the detonation properties of PETN, RDX and HMX explosives are calculated. The detonation velocity, pressure and temperature at CJ point are in good agreement with the experimental data.
The equilibrium compositions of detonation products of PETN, RDX and HMX explosives are calculated by solving chemical equilibrium equations based on minimizing Gibbs free energy. The results are in good agreement with the results obtained based on BKW and LJD equations of state. The Gibbs free energy of carbon is calculated based on the most probable state of dissociated carbon in detonation products, which is determined by distinguishing the following four states of carbon: graphite, diamond, graphitelike and diamondlike.The WCA equation is taken as the equation of state of detonation products, and the detonation properties of PETN, RDX and HMX explosives are calculated. The detonation velocity, pressure and temperature at CJ point are in good agreement with the experimental data.
2005, 25(4): 330-334.
doi: 10.11883/1001-1455(2005)04-0330-05
Abstract:
An experimental system of high-temperature split Hopkinson pressure bar (SHPB) was developed, and the dynamic properties of one type of antihydrogen steel at temperatures from room temperature to 1 000 ℃ and at strain rates from 500 to 1 000 s1 were studied using this system. The experimental system and the heated specimen were assembled rapidly by using a pneumatic mounting system to minimize the development of temperature gradients in the specimen. The experimental results show that the contact time is shorter than 500 ms. The softening effect of the antihydrogen steel due to heating is large, and the temperature sensitivity decreases quickly with the specimen temperature increasing.
An experimental system of high-temperature split Hopkinson pressure bar (SHPB) was developed, and the dynamic properties of one type of antihydrogen steel at temperatures from room temperature to 1 000 ℃ and at strain rates from 500 to 1 000 s1 were studied using this system. The experimental system and the heated specimen were assembled rapidly by using a pneumatic mounting system to minimize the development of temperature gradients in the specimen. The experimental results show that the contact time is shorter than 500 ms. The softening effect of the antihydrogen steel due to heating is large, and the temperature sensitivity decreases quickly with the specimen temperature increasing.
2005, 25(4): 335-340.
doi: 10.11883/1001-1455(2005)04-0335-06
Abstract:
Explosion seismic waves are numerically studied with a non-stationary random process model. Based on energy conservation and experiential relation, an envelope function of acceleration amplitude and power density of explosion seismic waves is proposed, in which the effects of distance and mass of explosive are considered. The model parameters are determined by using the measured data. A practical simulation method of single-point, two-point (little-difference) and multi-point (little-difference) explosion seismic waves is also presented. Numerical simulation results show that the simulated history of explosion seismic waves can well reproduce some characteristics of explosion seismic waves.
Explosion seismic waves are numerically studied with a non-stationary random process model. Based on energy conservation and experiential relation, an envelope function of acceleration amplitude and power density of explosion seismic waves is proposed, in which the effects of distance and mass of explosive are considered. The model parameters are determined by using the measured data. A practical simulation method of single-point, two-point (little-difference) and multi-point (little-difference) explosion seismic waves is also presented. Numerical simulation results show that the simulated history of explosion seismic waves can well reproduce some characteristics of explosion seismic waves.
2005, 25(4): 341-349.
doi: 10.11883/1001-1455(2005)04-0341-09
Abstract:
To create a mathematical model for the hydro-ballistic trajectory of high speed pellet entering water, the hydro-ballistic trajectory and cavity of sphere and pistol pellets entering water at three oblique angles and six velocities have been experimentally studied using a high-speed digital video recorder. The experimental results show that the shape of the pellet has significent influence on the hydro-trajectory stability. The hydro-ballistic trajectory of the sphere pellet obliquely entering water is more stable than that of the general pistol pellet. The initial cavity, ballistic trajectory and velocity attenuation of the sphere pellets are similar at different water-entry angles and initial velocities. The velocity of pellet in water decreases very quickly, and the attenuation is similar for both of the sphere and pistol pellets. A calculation model is proposed to predict the velocity attenuation of the pellet. Calculated results are in good agreement with the experimental.
To create a mathematical model for the hydro-ballistic trajectory of high speed pellet entering water, the hydro-ballistic trajectory and cavity of sphere and pistol pellets entering water at three oblique angles and six velocities have been experimentally studied using a high-speed digital video recorder. The experimental results show that the shape of the pellet has significent influence on the hydro-trajectory stability. The hydro-ballistic trajectory of the sphere pellet obliquely entering water is more stable than that of the general pistol pellet. The initial cavity, ballistic trajectory and velocity attenuation of the sphere pellets are similar at different water-entry angles and initial velocities. The velocity of pellet in water decreases very quickly, and the attenuation is similar for both of the sphere and pistol pellets. A calculation model is proposed to predict the velocity attenuation of the pellet. Calculated results are in good agreement with the experimental.
2005, 25(4): 350-354.
doi: 10.11883/1001-1455(2005)04-0350-05
Abstract:
PVDF pressure sensor has been developed to measure shock waves in concrete structures. The work principle and design methodology of the sensor are briefly introduced. Stable capacity of the sensor has been verified through calibration tests, and the measuring error of the sensor can be reduced by sensitivity correction. Finally, application in stress wave measurement of explosion in concrete is discussed.
PVDF pressure sensor has been developed to measure shock waves in concrete structures. The work principle and design methodology of the sensor are briefly introduced. Stable capacity of the sensor has been verified through calibration tests, and the measuring error of the sensor can be reduced by sensitivity correction. Finally, application in stress wave measurement of explosion in concrete is discussed.
2005, 25(4): 355-360.
doi: 10.11883/1001-1455(2005)04-0355-06
Abstract:
This paper presents a vaporization model of remnant propellant on the ground and a diffusion model of the poisonous gas for liquid hypergolic propellant launch vehicle explosion. The estimated mass of remnant propellant on the ground, the equivalent diameter of contaminated zone and the evaporation rate of N2O4 and UDMH are conducted for a N2O4/UDMH liquid propellant explosion respectively. The present models are applicable for predicting the vaporization (time) of remnant propellant on the ground and the contaminated range of poisonous gas for large scale liquid hypergolic propellant launch vehicle explosions. It provides an available evaluation method for safety measurement at the space vehicle launching site.
This paper presents a vaporization model of remnant propellant on the ground and a diffusion model of the poisonous gas for liquid hypergolic propellant launch vehicle explosion. The estimated mass of remnant propellant on the ground, the equivalent diameter of contaminated zone and the evaporation rate of N2O4 and UDMH are conducted for a N2O4/UDMH liquid propellant explosion respectively. The present models are applicable for predicting the vaporization (time) of remnant propellant on the ground and the contaminated range of poisonous gas for large scale liquid hypergolic propellant launch vehicle explosions. It provides an available evaluation method for safety measurement at the space vehicle launching site.
2005, 25(4): 361-367.
doi: 10.11883/1001-1455(2005)04-0361-07
Abstract:
Based on large deformation dynamic equation and finite difference method, the elastic-plastic dynamic responses of a fully clamped shallow arch subjected to projectile impact were studied numerically. Through analyzing the instantaneous distribution of the internal forces during early time response, the elastic-plastic deformation mechanism and mode were illustrated. The deformation mode consists of six phases. In the early phase of impact, the propagation of plastic bending deformation from the impact point to the root of arch dominated the deformation mode. While in the later phase, the deformation of axial tension governed by the axial force was dominant. Under the high-velocity projectile impact, the uneven plastic bending deformation can cause the arch to produce reversed flexural deformation. It can also be seen that the dynamic response of arch was very sensitive to a certain range of impact speed. In this range, tiny increase of initial projectile velocity can cause rapid increase of displacement. However, variation of dynamic response with impact speed was continuous without abrupt lose of stability. Numerical results were in good agreement with the experimental results from literature [5].
Based on large deformation dynamic equation and finite difference method, the elastic-plastic dynamic responses of a fully clamped shallow arch subjected to projectile impact were studied numerically. Through analyzing the instantaneous distribution of the internal forces during early time response, the elastic-plastic deformation mechanism and mode were illustrated. The deformation mode consists of six phases. In the early phase of impact, the propagation of plastic bending deformation from the impact point to the root of arch dominated the deformation mode. While in the later phase, the deformation of axial tension governed by the axial force was dominant. Under the high-velocity projectile impact, the uneven plastic bending deformation can cause the arch to produce reversed flexural deformation. It can also be seen that the dynamic response of arch was very sensitive to a certain range of impact speed. In this range, tiny increase of initial projectile velocity can cause rapid increase of displacement. However, variation of dynamic response with impact speed was continuous without abrupt lose of stability. Numerical results were in good agreement with the experimental results from literature [5].
2005, 25(4): 368-373.
doi: 10.11883/1001-1455(2005)04-0368-06
Abstract:
Advantages and disadvantages of classical and some modified methods for SHPB data processing are discussed. Errors brought by using the classical methods under different experimental conditions are analyzed. Results show that the three-wave method which calculate the stress and strain with absolute time holds the best reliability and requires the least artificial correction, and the classical two-wave method is not a good choice for data processing in any circumstances. A simplified three-wave method is also proposed for some cases where three-wave measurement is impossible.
Advantages and disadvantages of classical and some modified methods for SHPB data processing are discussed. Errors brought by using the classical methods under different experimental conditions are analyzed. Results show that the three-wave method which calculate the stress and strain with absolute time holds the best reliability and requires the least artificial correction, and the classical two-wave method is not a good choice for data processing in any circumstances. A simplified three-wave method is also proposed for some cases where three-wave measurement is impossible.
2005, 25(4): 374-377.
doi: 10.11883/1001-1455(2005)04-0374-04
Abstract:
This paper presents the design idea, work principle, main structure, technical indexes, and applications of a large-caliber mock missile launcher.
This paper presents the design idea, work principle, main structure, technical indexes, and applications of a large-caliber mock missile launcher.
2005, 25(4): 378-381.
doi: 10.11883/1001-1455(2005)04-0378-04
Abstract:
In order to exactly predict the velocity of EFP, its formation process is divided into a loading phase by high explosives and a self-deforming phase. It is assumed that the process ends at the time when the whole liner has melted, and the deformation energy consumed by the liner is equal to its melting energy. Accordingly, a velocity formula of EFP is proposed based on the law of energy conservation. The results are in good agreement with those from an experiment and a numerical simulation, demonstrating the applicability of this formula in engineering computation.
In order to exactly predict the velocity of EFP, its formation process is divided into a loading phase by high explosives and a self-deforming phase. It is assumed that the process ends at the time when the whole liner has melted, and the deformation energy consumed by the liner is equal to its melting energy. Accordingly, a velocity formula of EFP is proposed based on the law of energy conservation. The results are in good agreement with those from an experiment and a numerical simulation, demonstrating the applicability of this formula in engineering computation.
2005, 25(4): 382-384.
doi: 10.11883/1001-1455(2005)04-0382-03
Abstract:
Free surface velocity histories of a film flyer driven by electrical gun at charging voltage of 18 kV were measured using bi-sensitivity VISAR. The experimental setup, testing method, and experimental results are given in this paper. Several key factors for velocity measurement are discussed. The whole testing process lasted 1.6 s, and the final velocity reached at 6.7 km/s.
Free surface velocity histories of a film flyer driven by electrical gun at charging voltage of 18 kV were measured using bi-sensitivity VISAR. The experimental setup, testing method, and experimental results are given in this paper. Several key factors for velocity measurement are discussed. The whole testing process lasted 1.6 s, and the final velocity reached at 6.7 km/s.
