Investigation On Cylindrical Metal Tube Deforming By Laser-induced High-pressure Plasma

The high-temperature and high-pressure plasma induced by laser irradiation causes stress wave and deforms metal sheet.Laser shock forming technology has been applied in aerospace,medical equipment and other fields,which has an important research value.In this article,the diffusion mechanism of laser-induced plasma was researched by the combination of simulation and experiment methods.On this basis,the diffusion mechanism of high-pressure plasma at the surface of a circular cone in the circular tube had been further analyzed.The feasibility of cylindrical tube deforming by laser-induced high-pressure plasma had been verified,and the influencing factors of tube deformation process and deformation results are analyzed.In this paper,the main work and conclusions are as follows:(1)Under two different constraint conditions,the diffusion process of high-pressure plasma was numerically simulated by using fluid software,and the plasma-diffusion characteristics were discussed in detail.The trend of the pressure curve derived from the simulation results is consistent with the one resulted from previous experimental measurement and pressure momentum is similar,which verifies the feasibility of using the fluid model to study the laser-induced plasma detonation wave.(2)The high-pressure plasma diffusion model in the circular tube was established.The detonation-wave flow field in the round tube formed by the lateral expansion of the plasma was discussed in detail.And the pressure distribution curves were derived from the numerical simulation results.According to the principle of conservation of momentum,the non-uniform pressure curves are normalized and the pressure distribution function expression can be fitted to obtain.Results indicated that the circular cone of the impact effect on the tube wall that was induced by the plasma diffusion,which was stronger than that on the plane,and the impact effect of the plasma was enhanced as the cone angle decreasing.It is nearly linear relationship between the initial plasma pressure and pressure momentum,and the pressure loading duration is similar.(3)The finite element model for cylindrical tube deforming had been established,and the pressure distribution function of the tube wall was written into the model.The results show that the circular tube deformed plastically when the initial pressure of the plasma is 2GPa,which the maximum deformation depth is 0.674 mm.With the initial pressure of laserinduced plasma increasing,the maximum deformation depth of tube increased.The pressureloading position has an influence on the deformation depth of tube within the range of 0~0.7 mm.The closer the pressure-loading position is to the end surface of the tube,the larger the deformation depth of tube is.A reflecting cone is conducive to the tube deformation with an angle of 90°.The thinner and softer tube is conductive to the tube deformation.In general,the larger the tube deformation depth is,the thinner the wall thickness is.(4)The tube wall is plastically deformed when 5 J laser energy was used.For the experiment,the deformation depth and the length of the deformation area of the round pipe are similar to the results of the round pipe deformation when the initial pressure is 1.2 GPa in the simulation,which verifies the feasibility of cylindrical tube deforming by highpressure plasma and the reliability of the finite element model.In this study,when the pressure loading position is within the range of 0 ~ 0.5 mm,it has a significant impact on tube deformation.When the number of laser shocks increased from 1 to 5,the depth of tube deformation increased from 0.202 mm to 0.252 mm,and the length of tube deformation area increased from 3.3 mm to 3.758 mm.