激光功率密度对小孔构件残余应力场的影响

Analysis of the residual stress field in hole specimen by laser shock processing with different power density

激光冲击强化通过强激光诱导的冲击波在金属材料表层引入残余压应力,从而抑制疲劳裂纹的萌生和发展,是一种新型的金属表面强化技术。以ABAQUS有限元软件为平台,研究了不同激光功率密度下7050-T7451铝合金小孔构件的残余应力的分布。结果表明,冲击表面残余压应力在X轴方向上0～6 mm区域内分布很均匀,能量的变化对它的影响不是很大,表面最大残余压应力都出现在孔边缘处,整个冲击区域残余应力差别不大,构件单面冲击下表面只有残余压应力,然而并不是随着峰值压力的增加为增加,这是由于未冲击表面的残余压应力是由板料变形引起的。构件厚度方向残余压应力的深度随着冲击波的峰值压力的增大而增大,同时也造成板料厚度中心靠近上表面处产生过大的残余拉应力,这对提高材料的抗疲劳性能是极为不利的。

Laser shock processing is a new technique for fasten holes and the key is how to set the parameters of laser shock processing（LSP）.Finite element method has been used to predict the distribution of residual stress with different power density.FEA code ABAQUS is used as a platform to study the residual stress field with different power density.The result indicates that the residual stress distribution caused by different power density within 0~6 mm are basically uniform,the biggest residual compressive stress emerges in the hole edge,the impact region is not very different.In un-impacted side,there is only residual compressive stress,which is induced by the sheet metal′s deformation.With the increase of peak pressure,the residual compressive stress in hole inner wall is also increased,which also causes overlarge residual tensile stress near the center of sheet thickness direction,it is very adverse to improve the resistance of the fatigue performance.