In the current practical science, the accuracy in the formability of metal alloys being the goal when using electromagnetic forming (EMF) technology, which is a high-speed processing technology that uses Lorentz force...In the current practical science, the accuracy in the formability of metal alloys being the goal when using electromagnetic forming (EMF) technology, which is a high-speed processing technology that uses Lorentz forces to achieve plastic deformation of sheet metal;according to the previous analysis, the results have shown that in most cases, the Lorentz force acting on the workpiece (metal) is not uniform, there are uneven axial deformations of the metal plates which prevent the rapid advancement of today’s technology. In this article, we presented some advanced analyzes which will lead us to improve the technical solution for the problems of non-uniform axial deformations of the metals in the traditional tube electromagnetic forming technology (EMF). A field shaper is used as a practical forming tool to influence the magnetic field and magnetic pressure distribution, thereby improving the forming ability and result during the electromagnetic forming (EMF) process and we see that induced eddy current control is realized by changing the structural parameters of the magnetic field shaper;which improves the strength and controllability of the magnetic force that acts on the workpiece;thereby a greater radial magnetic pressure can be achieved with field shaper than the case without it;the field shaper regulates the electromagnetic force, the distribution of the magnetic pressure decreases, and the uniform force area of the tube increases which effectively enhances the uniform range of the pipe electromagnetic bulging and the electromagnetic induction coupling between the coil and the metallic workpiece is generally required to produce the Lorentz forces. Using COMSOL Multiphysics® simulation software helped us to accurately represent the real world, simulating multiple physical effects that happened in this model during the process.展开更多
Wave shaper effect on formation behavior and penetration performance of reactive liner shaped charge(RLSC)are investigated by experiments and simulations.The reactive materials liner with a density of2.3 g/cm^3 is fab...Wave shaper effect on formation behavior and penetration performance of reactive liner shaped charge(RLSC)are investigated by experiments and simulations.The reactive materials liner with a density of2.3 g/cm^3 is fabricated by cold pressing at a pressure of 300 MPa and sintering at a temperature of 380℃.Experiments of the RLSC with and without wave shaper against steel plates are carried out at standoffs of0.5,1.0,and 1.5 CD(charge diameter),respectively.The experimental results show that the penetration depths and structural damage effects of steel plates decrease with increasing the standoff,while the penetration depths and the damage effects of RLSC without wave shaper are much greater than that with wave shaper at the same standoff.To understand the unusual experimental results,numerical simulations based on AUTODYN-2 D code are conducted to discuss the wave shaper effect,including the propagation behavior of detonation wave,the velocity and temperature distribution of reactive jet,and penetration depth of reactive jet.The simulations indicate that,compared with RLSC without wave shaper,there is a higher temperature produced inside reactive jet with wave shaper.This unusual temperature rise effects are likely to be an important mechanism to cause the initiation delay time of reactive jet to decline,which results in significantly decreasing its penetration performance.展开更多
In the current study, streak camera was used to find concentricity of the assembly during detonation,investigate and compare shock front within the high explosive and behavior of the shock front on the surface of the ...In the current study, streak camera was used to find concentricity of the assembly during detonation,investigate and compare shock front within the high explosive and behavior of the shock front on the surface of the liner, one containing wave shaper and the other without wave shaper. Streaks revealed that the whole assembly was concentric till the formation of the jet. Observed streaks vindicate the uniform propagation of shock front in both the cases. Results obtained for shock front velocities are in agreement with those obtained from simulations. In the presence of wave shaper higher shock front velocity was observed both in simulation and experiment. Simulation without wave-shaper showed that shock front struck the copper cone at grazing angle while in the presence of wave-shaper it struck at an angle of 125.展开更多
In this paper,we present a novel ultrashort pulse shaper based on complex-modulated long-period-grating coupler（CM-LPGC）.Temporal rectangular waveform with 2-ps full width at half maximum（FWHM） is obtained by tran...In this paper,we present a novel ultrashort pulse shaper based on complex-modulated long-period-grating coupler（CM-LPGC）.Temporal rectangular waveform with 2-ps full width at half maximum（FWHM） is obtained by transforming the input Gaussian pulse.Tolerances of the CM-LPGC-based shaper to various non-ideal excitation conditions and fabricating errors are investigated.Results confirm that CM-LPGC is stable and suitable for optical pulse shaping operation.展开更多
Radioactive Ion Beam Line in Lanzhou (RIBLL) is the heavy ion radiation beam equipment on Heavy Ion Accelerator in Lanzhou, which can provide a variety of Radioactive Ion Beam （RIB）for physical experiments.In order ...Radioactive Ion Beam Line in Lanzhou (RIBLL) is the heavy ion radiation beam equipment on Heavy Ion Accelerator in Lanzhou, which can provide a variety of Radioactive Ion Beam （RIB）for physical experiments.In order to improve the efficiency and accuracy of the experiments, we need a high-performance Parallel Plate Avalanche Counter(PPAC) to monitor the RIB online and to measure the track of the incident particles and reaction products.展开更多
The Split Hopkinson Pressure Bar(SHPB) technique with a special experimental apparatus can be used to obtain the material behaviors under high strain rate loading condition. Attempts to apply the Split Hopkison Pressu...The Split Hopkinson Pressure Bar(SHPB) technique with a special experimental apparatus can be used to obtain the material behaviors under high strain rate loading condition. Attempts to apply the Split Hopkison Pressure Bar in measurement on polymeric materials suffer from limitations on the maximum achievable strain and from high noise to signal ratios. This paper introduces a Split Hopkinson Pressure Bar technique, to overcome these limitations. The proposed method uses aluminum pressure bars to achieve a closer impedance match between the pressure bars and the specimen materials, thus providing both data having a low noise to signal ratio and a longer input pulse at higher maximum strain. In addition, a pulse shaper technique was used for increasing the rise time of the incident pulse to ensure stress equilibrium and homogeneous deformation in the specimen under dynamic compression. A pulse shaper is utilized to lengthen the rising time of the incident pulse to ensure stress equilibrium and homogeneous deformation of polycarbonate. The dynamic deformation behaviors of Polymeric material under compressive high strain rate are evaluated using the modified SHPB technique.展开更多
In this paper,the influence of various field shapers and their shapes on the distribution of the magnetic flux densities and applied forces on the work-piece in the electromagnetic inward tube forming are studied nume...In this paper,the influence of various field shapers and their shapes on the distribution of the magnetic flux densities and applied forces on the work-piece in the electromagnetic inward tube forming are studied numerically using the FEA software MAXWELL.First the model was verified with experimental results and thereafter four kinds of field shapers(conical,cylindrical,concave and convex)were considered.Effects of their geometries,such as air gap between field shaper and tube work-piece,height of the step in single and multiple stepped field shaper on magnetic flux densities and magnetic pressures were studied.The results of this research can be applied to design field shaper,tube compression technology,and improve the efficiency of the coil.It is seen that magnetic force decreases if height of step in convex field shaper increases but effective forming region enlarges.Decreasing air gap has also a positive influence on magnetic field increase.Though the object of this research is limited to field shaper for inward tube forming,the results can also be applied to the field shaper for tube bulging.展开更多
文摘In the current practical science, the accuracy in the formability of metal alloys being the goal when using electromagnetic forming (EMF) technology, which is a high-speed processing technology that uses Lorentz forces to achieve plastic deformation of sheet metal;according to the previous analysis, the results have shown that in most cases, the Lorentz force acting on the workpiece (metal) is not uniform, there are uneven axial deformations of the metal plates which prevent the rapid advancement of today’s technology. In this article, we presented some advanced analyzes which will lead us to improve the technical solution for the problems of non-uniform axial deformations of the metals in the traditional tube electromagnetic forming technology (EMF). A field shaper is used as a practical forming tool to influence the magnetic field and magnetic pressure distribution, thereby improving the forming ability and result during the electromagnetic forming (EMF) process and we see that induced eddy current control is realized by changing the structural parameters of the magnetic field shaper;which improves the strength and controllability of the magnetic force that acts on the workpiece;thereby a greater radial magnetic pressure can be achieved with field shaper than the case without it;the field shaper regulates the electromagnetic force, the distribution of the magnetic pressure decreases, and the uniform force area of the tube increases which effectively enhances the uniform range of the pipe electromagnetic bulging and the electromagnetic induction coupling between the coil and the metallic workpiece is generally required to produce the Lorentz forces. Using COMSOL Multiphysics® simulation software helped us to accurately represent the real world, simulating multiple physical effects that happened in this model during the process.
基金funded under the National Natural Science Foundation of China (No. U1730112)supported by the State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology
文摘Wave shaper effect on formation behavior and penetration performance of reactive liner shaped charge(RLSC)are investigated by experiments and simulations.The reactive materials liner with a density of2.3 g/cm^3 is fabricated by cold pressing at a pressure of 300 MPa and sintering at a temperature of 380℃.Experiments of the RLSC with and without wave shaper against steel plates are carried out at standoffs of0.5,1.0,and 1.5 CD(charge diameter),respectively.The experimental results show that the penetration depths and structural damage effects of steel plates decrease with increasing the standoff,while the penetration depths and the damage effects of RLSC without wave shaper are much greater than that with wave shaper at the same standoff.To understand the unusual experimental results,numerical simulations based on AUTODYN-2 D code are conducted to discuss the wave shaper effect,including the propagation behavior of detonation wave,the velocity and temperature distribution of reactive jet,and penetration depth of reactive jet.The simulations indicate that,compared with RLSC without wave shaper,there is a higher temperature produced inside reactive jet with wave shaper.This unusual temperature rise effects are likely to be an important mechanism to cause the initiation delay time of reactive jet to decline,which results in significantly decreasing its penetration performance.
文摘In the current study, streak camera was used to find concentricity of the assembly during detonation,investigate and compare shock front within the high explosive and behavior of the shock front on the surface of the liner, one containing wave shaper and the other without wave shaper. Streaks revealed that the whole assembly was concentric till the formation of the jet. Observed streaks vindicate the uniform propagation of shock front in both the cases. Results obtained for shock front velocities are in agreement with those obtained from simulations. In the presence of wave shaper higher shock front velocity was observed both in simulation and experiment. Simulation without wave-shaper showed that shock front struck the copper cone at grazing angle while in the presence of wave-shaper it struck at an angle of 125.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61007007 and 61101110)the Foundation of Beijing Municipal Committee of CPC Organization Department (Grant No. 2012D005002000001)
文摘In this paper,we present a novel ultrashort pulse shaper based on complex-modulated long-period-grating coupler（CM-LPGC）.Temporal rectangular waveform with 2-ps full width at half maximum（FWHM） is obtained by transforming the input Gaussian pulse.Tolerances of the CM-LPGC-based shaper to various non-ideal excitation conditions and fabricating errors are investigated.Results confirm that CM-LPGC is stable and suitable for optical pulse shaping operation.
文摘Radioactive Ion Beam Line in Lanzhou (RIBLL) is the heavy ion radiation beam equipment on Heavy Ion Accelerator in Lanzhou, which can provide a variety of Radioactive Ion Beam （RIB）for physical experiments.In order to improve the efficiency and accuracy of the experiments, we need a high-performance Parallel Plate Avalanche Counter(PPAC) to monitor the RIB online and to measure the track of the incident particles and reaction products.
文摘The Split Hopkinson Pressure Bar(SHPB) technique with a special experimental apparatus can be used to obtain the material behaviors under high strain rate loading condition. Attempts to apply the Split Hopkison Pressure Bar in measurement on polymeric materials suffer from limitations on the maximum achievable strain and from high noise to signal ratios. This paper introduces a Split Hopkinson Pressure Bar technique, to overcome these limitations. The proposed method uses aluminum pressure bars to achieve a closer impedance match between the pressure bars and the specimen materials, thus providing both data having a low noise to signal ratio and a longer input pulse at higher maximum strain. In addition, a pulse shaper technique was used for increasing the rise time of the incident pulse to ensure stress equilibrium and homogeneous deformation in the specimen under dynamic compression. A pulse shaper is utilized to lengthen the rising time of the incident pulse to ensure stress equilibrium and homogeneous deformation of polycarbonate. The dynamic deformation behaviors of Polymeric material under compressive high strain rate are evaluated using the modified SHPB technique.
文摘In this paper,the influence of various field shapers and their shapes on the distribution of the magnetic flux densities and applied forces on the work-piece in the electromagnetic inward tube forming are studied numerically using the FEA software MAXWELL.First the model was verified with experimental results and thereafter four kinds of field shapers(conical,cylindrical,concave and convex)were considered.Effects of their geometries,such as air gap between field shaper and tube work-piece,height of the step in single and multiple stepped field shaper on magnetic flux densities and magnetic pressures were studied.The results of this research can be applied to design field shaper,tube compression technology,and improve the efficiency of the coil.It is seen that magnetic force decreases if height of step in convex field shaper increases but effective forming region enlarges.Decreasing air gap has also a positive influence on magnetic field increase.Though the object of this research is limited to field shaper for inward tube forming,the results can also be applied to the field shaper for tube bulging.
