Experimental And Numerical Simulation Of Micro-particle Shot Peening To Eliminate Welding Residual Stress

Welded joints are widely used in various large-scale mechanical equipment,such as aviation,nuclear industry,shipbuilding and machinery manufacturing.Due to the influence of welding residual tensile stress,the bearing capacity of welded joints is reduced,and the deformation of welded joints occurs.As the weak part of welding component,welding joint is prone to crack,corrosion cracking and fatigue failure.Therefore,eliminating welding residual tensile stress can not only improve the mechanical properties and service life of welded joints,but also reduce the occurrence of failure accidents of welded joints.Particle peening is a kind of surface nano technology which is different from the traditional peening.It can eliminate the residual tensile stress and introduce the high residual compressive stress on the surface,reduce the surface roughness of the welded joint,improve the surface hardness,fatigue strength and wear resistance by using particles with smaller diameter to impact the surface of the welded joint at a very fast speed.In this paper,S30408 austenitic stainless steel welded joint is taken as the research object.Combined with experimental research and numerical simulation,the mechanism of surface strengthening of welded joint by particle peening technology is explored,and the distribution and evolution of residual stress field are analyzed,which provides theoretical basis for the engineering significance of eliminating welding residual stress by this technology.The main research contents are as follows:(1)Experimental study on the elimination of welding residual tensile stress by particle peening.The welding joint of S30408 austenitic stainless steel was prepared and shot peened.The residual stress of the welded joint before and after the shot peening was measured by X-ray diffraction,and the influence of different shot peening process parameters on the removal of residual tensile stress was analyzed.The experimental results show that the maximum residual tensile stress is almost the yield strength of the material.After shot peening,the residual tensile stress disappears and transforms into residual compressive stress.Under the condition of complete coverage,the greater the shot peening strength is,the more obvious the influence is on the elimination of welding residual tensile stress,which is beneficial to improve the mechanical properties of welded joints.(2)A three-dimensional finite element model is established to simulate the initial welding residual stress field.Considering the influence of temperature on the physical properties of the material and the influence of the surrounding convection and radiation on the simulation results,the cell activation technology and the Gauss distribution heat source method are used to simulate the multi pass butt welding process of s30408.The temperature field and welding residual stress field of s30408 welding joint are simulated.Compared with the test results,the results show that the transient temperature field and the distribution of residual stress field after welding are basically consistent,which ensures that the initial residual stress value of the particle peening model is consistent with the initial residual stress value of the particle peening experiment.(3)Numerical simulation study on the elimination of welding residual stress by particle peening.The single particle model,symmetrical cell particle model and random probability distribution particle model are established.The effects of particle diameter and particle velocity on eliminating residual tensile stress are compared and analyzed.The results show that the simulation results are basically consistent with the test results,which shows that the numerical simulation method can more accurately simulate the particle shot peening to eliminate welding residual tensile stress.Under the same coverage rate,compared with small diameter and low speed particle peening,the compressive stress value formed by large diameter and high speed particle peening is larger and the strengthening depth is deeper.