Shock wave is emitted into the plate and sphere when a sphere hypervelocity impacts onto a thin plate.The fragmentation and phase change of the material caused by the propagation and unloading of shock wave could resu...Shock wave is emitted into the plate and sphere when a sphere hypervelocity impacts onto a thin plate.The fragmentation and phase change of the material caused by the propagation and unloading of shock wave could result in the formation of debris cloud eventually.Propagation models are deduced based on one-dimensional shock wave theory and the geometry of sphere,which uses elliptic equations(corresponding to ellipsoid equations in physical space)to describe the propagation of shock wave and the rarefaction wave.The“Effective thickness”is defined as the critical plate thickness that ensures the rarefaction wave overtake the shock wave at the back of the sphere.The“Effective thickness”is directly related to the form of the debris cloud.The relation of the“Effective thickness”and the“Optimum thickness”is also discussed.The impacts of Al spheres onto Al plates are simulated within SPH to verify the propagation models and associated theories.The results show that the wave fronts predicted by the propagation models are closer to the simulation result at higher impact velocity.The curvatures of the wave fronts decrease with the increase of impact velocities.The predicted“Effective thickness”is consistent with the simulation results.The analysis about the shock wave propagation and unloading in this paper can provide a new sight and inspiration for the quantitative study of hypervelocity impact and space debris protection.展开更多
The double casing warhead with sandwiched charge is a novel fragmentation warhead that can produce two groups of fragments with different velocity,and the previous work has presented a calculation formula to determine...The double casing warhead with sandwiched charge is a novel fragmentation warhead that can produce two groups of fragments with different velocity,and the previous work has presented a calculation formula to determine the maximum fragment velocity.The current work builds on the published formula to further develop a formula for calculating the axial distribution characteristics of the fragment velocity.For this type of warhead,the simulation of the dispersion characteristics of the detonation products at different positions shows that the detonation products at the ends have a much larger axial velocity than those in the middle,and the detonation products have a greater axial dispersion velocity when they are closer to the central axis.The loading process and the fragment velocity vary with the axial position for both casing layers,and the total velocity of the fragments is the vector sum of the radial velocity and the axial velocity.At the same axial position,the acceleration time of the inner casing is greater than that of the outer casing.For the same casing,the fragments generated at the ends have a longer acceleration time than the fragments from the middle.The proposed formula is validated with the X-ray radiography results of the four warheads previously tested experimentally and the 3D smoothedparticle hydrodynamics numerical simulation results of several series of new warheads with different configurations.The formula can accurately and reliably calculate the fragment velocity when the lengthto-diameter ratio of the charge is greater than 1.5 and the thickness of the casing is less than 20%its inner radius.This work thus provides a key reference for the theoretical analysis and the design of warheads with multiple casings.展开更多
A systematic investigation on the mechanism of dynamic liquid dispersing process via theoretical and experimental approach is presented.The experiments include weak and strong constrained scenarios using the high-spee...A systematic investigation on the mechanism of dynamic liquid dispersing process via theoretical and experimental approach is presented.The experiments include weak and strong constrained scenarios using the high-speed camera technique and the flash X-ray radiography technique.Based on dynamic analysis,one-dimensional characteristics analysis and some numerical simulations on the propagating processes of blast waves before the container shell rupturing,further and detailed analyses of the experimental results are presented.The effects of the liquid viscosity on the dynamic dispersing flow are also analyzed,and the spall fracture mechanism is explored.Thus,the dominating forces determining the dispersing liquid flow are revealed,that is,the stretching and shearing action due to the interaction of two reflecting rarefaction waves in opposite propagating directions.The influence of container shell strength on the dispersing liquid flow is also investigated,and the characters of cavitation layered in liquid before shell rupturing are uncovered.Results revealed that different shell material results in different cavitating layers.Then the different cavitating layers drive the different dynamic liquid dispersing process coming into being.The metastable liquid states caused by pressure drop and cavitation generation are discussed.展开更多
基金supported by the National Natural Science Foundation of China(11627901,11872118).
文摘Shock wave is emitted into the plate and sphere when a sphere hypervelocity impacts onto a thin plate.The fragmentation and phase change of the material caused by the propagation and unloading of shock wave could result in the formation of debris cloud eventually.Propagation models are deduced based on one-dimensional shock wave theory and the geometry of sphere,which uses elliptic equations(corresponding to ellipsoid equations in physical space)to describe the propagation of shock wave and the rarefaction wave.The“Effective thickness”is defined as the critical plate thickness that ensures the rarefaction wave overtake the shock wave at the back of the sphere.The“Effective thickness”is directly related to the form of the debris cloud.The relation of the“Effective thickness”and the“Optimum thickness”is also discussed.The impacts of Al spheres onto Al plates are simulated within SPH to verify the propagation models and associated theories.The results show that the wave fronts predicted by the propagation models are closer to the simulation result at higher impact velocity.The curvatures of the wave fronts decrease with the increase of impact velocities.The predicted“Effective thickness”is consistent with the simulation results.The analysis about the shock wave propagation and unloading in this paper can provide a new sight and inspiration for the quantitative study of hypervelocity impact and space debris protection.
基金supported by the National Natural Science Foundation of China(Grant No.11872121)。
文摘The double casing warhead with sandwiched charge is a novel fragmentation warhead that can produce two groups of fragments with different velocity,and the previous work has presented a calculation formula to determine the maximum fragment velocity.The current work builds on the published formula to further develop a formula for calculating the axial distribution characteristics of the fragment velocity.For this type of warhead,the simulation of the dispersion characteristics of the detonation products at different positions shows that the detonation products at the ends have a much larger axial velocity than those in the middle,and the detonation products have a greater axial dispersion velocity when they are closer to the central axis.The loading process and the fragment velocity vary with the axial position for both casing layers,and the total velocity of the fragments is the vector sum of the radial velocity and the axial velocity.At the same axial position,the acceleration time of the inner casing is greater than that of the outer casing.For the same casing,the fragments generated at the ends have a longer acceleration time than the fragments from the middle.The proposed formula is validated with the X-ray radiography results of the four warheads previously tested experimentally and the 3D smoothedparticle hydrodynamics numerical simulation results of several series of new warheads with different configurations.The formula can accurately and reliably calculate the fragment velocity when the lengthto-diameter ratio of the charge is greater than 1.5 and the thickness of the casing is less than 20%its inner radius.This work thus provides a key reference for the theoretical analysis and the design of warheads with multiple casings.
基金the support of National Nature Science Foundation of China, the support numbers are No. 10572149 and No.10676120the National Key Research and Development program of China (subject no. 2017YFC0209901) for its support to the work of this paper
文摘A systematic investigation on the mechanism of dynamic liquid dispersing process via theoretical and experimental approach is presented.The experiments include weak and strong constrained scenarios using the high-speed camera technique and the flash X-ray radiography technique.Based on dynamic analysis,one-dimensional characteristics analysis and some numerical simulations on the propagating processes of blast waves before the container shell rupturing,further and detailed analyses of the experimental results are presented.The effects of the liquid viscosity on the dynamic dispersing flow are also analyzed,and the spall fracture mechanism is explored.Thus,the dominating forces determining the dispersing liquid flow are revealed,that is,the stretching and shearing action due to the interaction of two reflecting rarefaction waves in opposite propagating directions.The influence of container shell strength on the dispersing liquid flow is also investigated,and the characters of cavitation layered in liquid before shell rupturing are uncovered.Results revealed that different shell material results in different cavitating layers.Then the different cavitating layers drive the different dynamic liquid dispersing process coming into being.The metastable liquid states caused by pressure drop and cavitation generation are discussed.
