激光冲击残余应力场的有限元分析

建立模拟激光冲击残余应力场的非线性弹塑性有限元模型,预测AISI 304奥氏体不锈钢厚、薄靶材经激光冲击后表面以及内部的残余应力场分布.模拟过程中,考虑材料高应变率(106s-1)下的力学性能和激光诱导冲击波的精确加载,分析激光功率密度、激光光斑尺寸、激光脉宽、激光冲击次数、激光单面与双面冲击等激光冲击参数以及初始残余应力等因素对不锈钢靶材残余应力分布的影响.数值模拟结果与X射线衍射法测量值吻合较好.在有初始残余拉应力(250MPa)存在的情况下,激光冲击仍能使304奥氏体不锈钢靶材形成残余压应力层,说明激光冲击工艺可提高奥氏体不锈钢焊接构件的抗应力腐蚀开裂能力.

Residual Stress Field Induced by Laser Peening: a Finite Element Analysis

A non-linear elastic-plastic finite element method to predict the residual stress distribution induced by Laser Shock Processing(LSP) in the AISI 304 stainless steel was established.This two dimensional FEA model considered the dynamic material properties at high strain rates(10~6s~(-1)) and the precise determination of loading conditions. Effects of laser power density,laser spot size,laser pulse duration,multiple LSP processes and one/two-sided LSP on the compressive stress field in the stainless steel were(evaluated) for the purpose of optimizing the process.Numerical results have a good agreement with the measurement values by X-ray diffraction method and also show that the magnitude of compressive stress induced by laser shock processing is more than the welding residual stress.Therefore,laser shock processing is an effective method for protecting weldments against stress corrosion crack.