摘要
激光冲击强化是一项高应变速率的表面强化技术,在材料表面产生的残余压应力表层可抑制疲劳裂纹的萌生和扩展。本文的目的是研究基于Ti-6Al-4V合金的方形光斑激光冲击强化产生应力空洞现象。建立了半无限有限元分析模型,用于分析从冲击波加载到静态平衡的激光冲击强化过程,其冲击波波形用三角波形近似代替。分析了方形光斑中心区域的塑性应变过程和动态应力,对比了不同冲击波峰值压力和不同冲击波宽度所产生最终平衡表面残余应力。模拟结果表明,由于表面瑞利波在光斑中心汇聚产生反向塑性变形后,光斑中心将产生应力空洞。当冲击波峰值压力增大后,应力空洞的严重程度和产生范围均增大。激光脉冲宽度足够小时,光斑中心将不会发生反向塑性变形。此外,在相同的冲击波峰值压力下,脉宽较短的激光脉冲照射在已经被脉宽较宽的激光脉冲强化的表面,在光斑中心由于应力空洞引起的下降残余压应力将再次升高。
Stress hole is an inevitable phenomenon on laser shock peening,and it reduces amplitudes and strengthening effects of compressive residual stresses on center area of laser shocked spots.The purpose of this paper is to investigate the phenomenon of stress hole on square-spot laser shock peening for Ti-6Al-4V alloy.A semi-infinite Finite Element Analysis modeling was built to simulate the process of laser shock peening from shock-wave loading to static equilibrium,and shock waves were set to act as initial condition,and its profiles were approximately replaced by triangular profiles.Plastic-strain histories and dynamic stresses at spot center were studied,and final surface residual stresses were investigated with different shock wave amplitudes and different shock wave durations.The simulation results show that stress holes appear at the center of laser spots when reverse plastic strains are produced by focused Rayleigh waves.It is found that magnitudes and ranges of stress holes both increase with increasing amplitudes of shockwave.The reverse plastic strains will not appear at spot center in case that the laser pulse duration is relatively short.In addition,after a shorter pulse laser incidents onto peened area which is peened by a wider pulse laser,compressive residual stresses at spot center can be enhanced.
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2013年第S2期222-225,共4页
Rare Metal Materials and Engineering
基金
NSFC(50824001)
关键词
激光冲击强化
应力空洞
应力缺乏
残余压应力
方形光斑
laser shock peening
stress hole
stress lack
compressive residual stresses
square spot
