2005 Vol. 25, No. 2
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2005, 25(2): 97-101.
doi: 10.11883/1001-1455(2005)02-0097-05
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Abstract:
For the problem of detonation driving plate, if some quantities could be gained from theories or experiments, we can deduce the projection angle formula from the projection angle equation. Using the equation, regarding the projection angle as a small quantity, neglecting the differentiation of the absolute value of the tangential velocity with respect to the time, the P.C.Chou formula was easily obtained. When considering the differentiation of the absolute value of the tangential velocity with respect to the time, the improved P.C.Chou formula was obtained. Compared to the P.C.Chou formula and Taylor formula, the results from the improved formula are more close to the experiment.
For the problem of detonation driving plate, if some quantities could be gained from theories or experiments, we can deduce the projection angle formula from the projection angle equation. Using the equation, regarding the projection angle as a small quantity, neglecting the differentiation of the absolute value of the tangential velocity with respect to the time, the P.C.Chou formula was easily obtained. When considering the differentiation of the absolute value of the tangential velocity with respect to the time, the improved P.C.Chou formula was obtained. Compared to the P.C.Chou formula and Taylor formula, the results from the improved formula are more close to the experiment.
2005, 25(2): 102-106.
doi: 10.11883/1001-1455(2005)02-0102-05
Abstract:
The numerical simulation result for the penetration of ceramic composite plate by long-rod projectile of tungsten alloy was presented. The front and back of the composite plate is made of armor steel and in the middle is ceramic. The Johnson-Cook constitutive equation was adopted to describe the deformations of the armor steel and the projectile. The Mohr-Coulomb cap model was combined with the Bodner-Partom constitutive equations to describe the comminuted strength and the flow stress of the ceramic. The iterative method using consistent mass matrix was used to improve the computation accuracy and the interface eroding technique was introduced to deal with the failure of the meshes. The computational results of the penetration depth are in agreement with the experiments.
The numerical simulation result for the penetration of ceramic composite plate by long-rod projectile of tungsten alloy was presented. The front and back of the composite plate is made of armor steel and in the middle is ceramic. The Johnson-Cook constitutive equation was adopted to describe the deformations of the armor steel and the projectile. The Mohr-Coulomb cap model was combined with the Bodner-Partom constitutive equations to describe the comminuted strength and the flow stress of the ceramic. The iterative method using consistent mass matrix was used to improve the computation accuracy and the interface eroding technique was introduced to deal with the failure of the meshes. The computational results of the penetration depth are in agreement with the experiments.
2005, 25(2): 107-111.
doi: 10.11883/1001-1455(2005)02-0107-05
Abstract:
By using complete soft recovery technique, the deformation and macroscopical spalling characteristics of steel 20 tube under sliding inward explosion were investigated. Experiments were carried out with different kinds of solid high explosives (HE), with several HE thicknesses, and under different outer shell conditions. The quantitative result of critical thickness of HE for steel tubes spalling was obtained, the influence of load intensity, HE thickness and outer shell on steel tubes spalling were also analyzed.
By using complete soft recovery technique, the deformation and macroscopical spalling characteristics of steel 20 tube under sliding inward explosion were investigated. Experiments were carried out with different kinds of solid high explosives (HE), with several HE thicknesses, and under different outer shell conditions. The quantitative result of critical thickness of HE for steel tubes spalling was obtained, the influence of load intensity, HE thickness and outer shell on steel tubes spalling were also analyzed.
2005, 25(2): 112-118.
doi: 10.11883/1001-1455(2005)02-0112-07
Abstract:
In this paper, using ANSYS 5.7/LS-DYNA, the dynamic stress concentration at the hole edge in a plate subjected to transverse explosive loading was studied. A simple and effective approach based on time-distributive function of energy density was developed to calculate the dynamic stress concentration factor. Numerical results are carried out for fixed supported and simple supported square plates (3 m3 m) with a hole (0.3 m0.3 m) in the center.
In this paper, using ANSYS 5.7/LS-DYNA, the dynamic stress concentration at the hole edge in a plate subjected to transverse explosive loading was studied. A simple and effective approach based on time-distributive function of energy density was developed to calculate the dynamic stress concentration factor. Numerical results are carried out for fixed supported and simple supported square plates (3 m3 m) with a hole (0.3 m0.3 m) in the center.
2005, 25(2): 119-124.
doi: 10.11883/1001-1455(2005)02-0119-06
Abstract:
The pressure-shear plate impact experiments and impact recovery experiments have been performed on 92.93% aluminas using 57 mm-diameter compressed-gas gun. And the inelastic behavior and shear wave propagation have been probed in polycrystalline ceramics under combined compression and shear loading. The compressed-gas gun drove the copper flyer to impact the oblique target parallelly, and the particle velocity is traced by embedded electromagnetic velocity gauge. The lateral particle velocities show an attenuation of shear waves with decreasing of material shear rigidity, which were decoupled from the histories of electromotive force induced by electromagnetic velocity gauges moving in magnetic field. Then SEM analysis of recovered samples shows the transit of intergranular microcracks to transgranular microcracks with increasing shock loading. Microcracks nucleate and expand along crystal boundaries and pores under loading of pressure-shear impact below the material yield threshold, and go further to transgranular microcracks with the loading above the yield threshold. The microcracks result in a remarkable dilation of alumina samples when unloaded.
The pressure-shear plate impact experiments and impact recovery experiments have been performed on 92.93% aluminas using 57 mm-diameter compressed-gas gun. And the inelastic behavior and shear wave propagation have been probed in polycrystalline ceramics under combined compression and shear loading. The compressed-gas gun drove the copper flyer to impact the oblique target parallelly, and the particle velocity is traced by embedded electromagnetic velocity gauge. The lateral particle velocities show an attenuation of shear waves with decreasing of material shear rigidity, which were decoupled from the histories of electromotive force induced by electromagnetic velocity gauges moving in magnetic field. Then SEM analysis of recovered samples shows the transit of intergranular microcracks to transgranular microcracks with increasing shock loading. Microcracks nucleate and expand along crystal boundaries and pores under loading of pressure-shear impact below the material yield threshold, and go further to transgranular microcracks with the loading above the yield threshold. The microcracks result in a remarkable dilation of alumina samples when unloaded.
2005, 25(2): 125-131.
doi: 10.11883/1001-1455(2005)02-0125-07
Abstract:
In this paper, the impact compression tests of the stress-strain curves of steel fiber reinforced high strength concrete got by 100 mm SHPB setup are introduced. From the compression strength, peak strain and the elastic modulu etc., the effects of strain rate on the impact compression of steel fiber reinforced concrete are discussed with the results of the same specimens under different strain rate. From the compression strength, peak strain and the toughness, the reinforcing effect and toughening effect of steel fiber are discussed.
In this paper, the impact compression tests of the stress-strain curves of steel fiber reinforced high strength concrete got by 100 mm SHPB setup are introduced. From the compression strength, peak strain and the elastic modulu etc., the effects of strain rate on the impact compression of steel fiber reinforced concrete are discussed with the results of the same specimens under different strain rate. From the compression strength, peak strain and the toughness, the reinforcing effect and toughening effect of steel fiber are discussed.
2005, 25(2): 132-136.
doi: 10.11883/1001-1455(2005)02-0132-05
Abstract:
Three different FAE devices were tested with the aspect ration of height to diameter ranged from 1.5 to 2.3 and high-speed video was used to detect the cloud formation. Based on the digital image-processing software and referenced to the upper close end of the device, the mass formula of the jet was deduced. The results indicate that jet formation of FAE depends on device height, material and liquid density. Jet formation for each device is more 10% than its total mass.
Three different FAE devices were tested with the aspect ration of height to diameter ranged from 1.5 to 2.3 and high-speed video was used to detect the cloud formation. Based on the digital image-processing software and referenced to the upper close end of the device, the mass formula of the jet was deduced. The results indicate that jet formation of FAE depends on device height, material and liquid density. Jet formation for each device is more 10% than its total mass.
Applications of the ghost fluid method based on the fourth-order semi-discrete central-upwind scheme
2005, 25(2): 137-144.
doi: 10.11883/1001-1455(2005)02-0137-08
Abstract:
A fourth-order semi-discrete central-upwind scheme for multidimensional inviscid compressible Euler equations is presented in this paper. Based on the local speeds of nonlinear wave propagation at grids boundaries, the width of the local Riemann fans are calculated more accurately. Thus the scheme enjoys a much smaller numerical viscosity, and the staggering between two sets of grids is avoided. Since the location of the interface can be tracked by Level Set function implicitly and the boundary conditions are implicitly captured by the construction of a ghost fluid, the scheme is combined with the Level Set method and the ghost fluid method. In this way, the non-reacting shock problems and detonation discontinuities in multimaterial flows are tracked successfully.
A fourth-order semi-discrete central-upwind scheme for multidimensional inviscid compressible Euler equations is presented in this paper. Based on the local speeds of nonlinear wave propagation at grids boundaries, the width of the local Riemann fans are calculated more accurately. Thus the scheme enjoys a much smaller numerical viscosity, and the staggering between two sets of grids is avoided. Since the location of the interface can be tracked by Level Set function implicitly and the boundary conditions are implicitly captured by the construction of a ghost fluid, the scheme is combined with the Level Set method and the ghost fluid method. In this way, the non-reacting shock problems and detonation discontinuities in multimaterial flows are tracked successfully.
2005, 25(2): 145-150.
doi: 10.11883/1001-1455(2005)02-0145-06
Abstract:
The experimental study of ultrafine aluminum oxide formed by the mixture detonation of aluminum nitrate and PETN used to maintain steady detonation is presented. The detonation product without any disposal is analysed by TEM、XRD、DTA/TGA and BET. The results show that the detonation product is ultrafine and globose aluminum oxide, the range of granularity is from 10~50 nm, the average size is 25 nm. The aluminum oxide is aluminum oxide. Based on the experimental results, we concluded that the ultrafine aluminum oxide directly agglomerated each other with the ion or molecule formed in the reaction area of detonation. Because the process of agglomeration and growth completed in the microsecond range, the grains did not grow towards the favored direction and took spherial form.
The experimental study of ultrafine aluminum oxide formed by the mixture detonation of aluminum nitrate and PETN used to maintain steady detonation is presented. The detonation product without any disposal is analysed by TEM、XRD、DTA/TGA and BET. The results show that the detonation product is ultrafine and globose aluminum oxide, the range of granularity is from 10~50 nm, the average size is 25 nm. The aluminum oxide is aluminum oxide. Based on the experimental results, we concluded that the ultrafine aluminum oxide directly agglomerated each other with the ion or molecule formed in the reaction area of detonation. Because the process of agglomeration and growth completed in the microsecond range, the grains did not grow towards the favored direction and took spherial form.
2005, 25(2): 151-156.
doi: 10.11883/1001-1455(2005)02-0151-06
Abstract:
Cellular patterns were recorded by smoke tracing technique, and evolution of cellular structure was analyzed in detail when gaseous detonation propagates in the 90 rectangular bend. The influences of initial pressure of combustible gas and curvature radii of 90 rectangular bend were also investigated. Initial pressures of combustible gas used in the experiments were 33.3, 26.7, 24.0, 16.0, 10.7 kPa, respectively. The curvature radii of rectangular bend were 100 mm and 50 mm. Study of evolution of detonation cell in the bend might further the understanding of the mechanism of gas detonation diffraction and improve the design of pipes in the petroleum or natural gas industry.
Cellular patterns were recorded by smoke tracing technique, and evolution of cellular structure was analyzed in detail when gaseous detonation propagates in the 90 rectangular bend. The influences of initial pressure of combustible gas and curvature radii of 90 rectangular bend were also investigated. Initial pressures of combustible gas used in the experiments were 33.3, 26.7, 24.0, 16.0, 10.7 kPa, respectively. The curvature radii of rectangular bend were 100 mm and 50 mm. Study of evolution of detonation cell in the bend might further the understanding of the mechanism of gas detonation diffraction and improve the design of pipes in the petroleum or natural gas industry.
2005, 25(2): 157-162.
doi: 10.11883/1001-1455(2005)02-0157-06
Abstract:
Experimental study of the response of the concrete, steel fiber reinforced concrete and polypropylene fiber reinfored concrete slab under blast loading was performed. The macroscopic damage is described, and the explosive compression coefficient values of three kind materials are obtained through apparent crater size fitting analysis. The ЛяхоB formula is used to fit the measured peak stress. The result shows that as the specimen thickness increases, the peak stress value will decrease, and the pressure value at same explosion distance will decrease as well. A formula that can be used to calculate the explosion perforation depth is obtained.
Experimental study of the response of the concrete, steel fiber reinforced concrete and polypropylene fiber reinfored concrete slab under blast loading was performed. The macroscopic damage is described, and the explosive compression coefficient values of three kind materials are obtained through apparent crater size fitting analysis. The ЛяхоB formula is used to fit the measured peak stress. The result shows that as the specimen thickness increases, the peak stress value will decrease, and the pressure value at same explosion distance will decrease as well. A formula that can be used to calculate the explosion perforation depth is obtained.
2005, 25(2): 163-170.
doi: 10.11883/1001-1455(2005)02-0163-08
Abstract:
The response of a transmission shaft in gear transmission system subjected to accidental impact by the joggled gear is simplified as that of a fully clamped beam stuck by an equivalent mass with an initial velocity, which is analyzed within the framework of rigid-plastic method. The effect of torsion is catered for in the Von Mises yield condition and that the strain rate effect is taken into account using Cowper-Symonds empirical constitutive equation. It is found that both the displacement and the rotation are relatively large and that the strain rate effect cannot be neglected. It is also found that the diameter of shaft is a crucial factor in the bending response.
The response of a transmission shaft in gear transmission system subjected to accidental impact by the joggled gear is simplified as that of a fully clamped beam stuck by an equivalent mass with an initial velocity, which is analyzed within the framework of rigid-plastic method. The effect of torsion is catered for in the Von Mises yield condition and that the strain rate effect is taken into account using Cowper-Symonds empirical constitutive equation. It is found that both the displacement and the rotation are relatively large and that the strain rate effect cannot be neglected. It is also found that the diameter of shaft is a crucial factor in the bending response.
2005, 25(2): 171-175.
doi: 10.11883/1001-1455(2005)02-0171-05
Abstract:
The paper discusses experimental results of launching truncated-ogive-nose earth penetrating weapon into concrete targets. The motion process of projectile is studied using the high-speed recording photographs of the reduce scale earth penetrating weapon penetrating process and test results. Velocity curves and resistance histories of truncated-ogive-nose earth penetrating weapon into concrete targets are recorded. At the same time, using reduce scale theory, computation method and analysis results of the penetrability are presented for standard earth penetrating weapon for concrete targets.
The paper discusses experimental results of launching truncated-ogive-nose earth penetrating weapon into concrete targets. The motion process of projectile is studied using the high-speed recording photographs of the reduce scale earth penetrating weapon penetrating process and test results. Velocity curves and resistance histories of truncated-ogive-nose earth penetrating weapon into concrete targets are recorded. At the same time, using reduce scale theory, computation method and analysis results of the penetrability are presented for standard earth penetrating weapon for concrete targets.
2005, 25(2): 176-179.
doi: 10.11883/1001-1455(2005)02-0176-04
Abstract:
The characteristics of explosive seismic source has been investigated with close-in ground motion data. On the assumption of half space model, the underground explosion seismic source function, i.e. reduced velocity potential (RVP), has been obtained deducting the ground surface response. The spectrum magnitude of RVP and its parameters including steady state value , frequency factor and overshoot B were obtained. The relationship between yield and source parameters of and were obtained as well.
The characteristics of explosive seismic source has been investigated with close-in ground motion data. On the assumption of half space model, the underground explosion seismic source function, i.e. reduced velocity potential (RVP), has been obtained deducting the ground surface response. The spectrum magnitude of RVP and its parameters including steady state value , frequency factor and overshoot B were obtained. The relationship between yield and source parameters of and were obtained as well.
2005, 25(2): 180-182.
doi: 10.11883/1001-1455(2005)02-0180-03
Abstract:
Series of small yield chemical explosion tests, which media were uniform near the explotion sources, were performed in a certain hard rock to investigate the relationship between explosion seismic coupling intensity and yield in the same buried depth. The magnitude spectra of explosion seismic function reduced velocity potential for two chemical explosions which yield ratio was two, were compared with the ground motion data to obtain that the seismic coupling ratio is approximately equal to two. Therefore, it was concluded that underground explosion seismic intensity be directly proportinal to yield in the same explosion depth.
Series of small yield chemical explosion tests, which media were uniform near the explotion sources, were performed in a certain hard rock to investigate the relationship between explosion seismic coupling intensity and yield in the same buried depth. The magnitude spectra of explosion seismic function reduced velocity potential for two chemical explosions which yield ratio was two, were compared with the ground motion data to obtain that the seismic coupling ratio is approximately equal to two. Therefore, it was concluded that underground explosion seismic intensity be directly proportinal to yield in the same explosion depth.
2005, 25(2): 183-188.
doi: 10.11883/1001-1455(2005)02-0183-06
Abstract:
The spall properties of no-Co-alloy steel loaded by gas gun are studied, and Hugoniot elastic limit, spall strength, spall thickness and plastic strain rate are obtained from each experiment. By the fracture analysis and metallographic analysis, we obtained the spall fracture mechanism at different strain rate. In addition, the spall fracture is simulated by LS-DYNA dynamic finite element code, and the simulation results agree well with that of the experiments.
The spall properties of no-Co-alloy steel loaded by gas gun are studied, and Hugoniot elastic limit, spall strength, spall thickness and plastic strain rate are obtained from each experiment. By the fracture analysis and metallographic analysis, we obtained the spall fracture mechanism at different strain rate. In addition, the spall fracture is simulated by LS-DYNA dynamic finite element code, and the simulation results agree well with that of the experiments.
2005, 25(2): 189-192.
doi: 10.11883/1001-1455(2005)02-0189-04
Abstract:
A mixture of HFC-161 used as an alternative refrigerant to R502 is promising. It is necessary to study the flammability of HFC-161 in order to ensure the safety in application. Follow GB/T12474-90, an experimental setup for explosion limits was established. The pure HFC-161 and the mixtures of HFC-125 and HFC-161 in different ratios were tested. Basing on the experimental data, the regularity of explosion limits was analyzed with mixtures composed of HFC-125 and HFC-161 in several different ratios. The results might be used as the basis for the evaluation of the explosion limits of the new ternary mixtures of HFC-161, HFC-125 and HFC-143a.
A mixture of HFC-161 used as an alternative refrigerant to R502 is promising. It is necessary to study the flammability of HFC-161 in order to ensure the safety in application. Follow GB/T12474-90, an experimental setup for explosion limits was established. The pure HFC-161 and the mixtures of HFC-125 and HFC-161 in different ratios were tested. Basing on the experimental data, the regularity of explosion limits was analyzed with mixtures composed of HFC-125 and HFC-161 in several different ratios. The results might be used as the basis for the evaluation of the explosion limits of the new ternary mixtures of HFC-161, HFC-125 and HFC-143a.
