Study on Residual Stress Distribution of 7050 Aluminum Sheet with Groove after Laser Shock Peening

激光强化后7050凹槽铝板的残余应力分布规律研究

¹ School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072, China
² AVIC The First Aircraft Institute, Xi'an 710089, China

Received: 12 September 2018

Abstract

In order to study the residual stress profile of 7050-T7451 aluminum sheet with groove after laser shock peening (LSP), the residual stress distribution was measured. It is shown that the residual stress decreases gradually from the center to the edge of groove; and then there is the minimum value at the edge of the groove bottom surface. By using ABAQUS software to establish three-dimensional finite element model for 7050 aluminum sheet with groove, and the load was applied by VDLOAD subroutine. The finite element analysis was performed and the analysis results were compared with the experimental measurements, in which the both the results agree with each other very well. And then the residual stress distribution of the sheet was analyzed after laser shock peening under different laser processing parameters. It is shown that the residual stress decreases firstly and then increases with the rise of laser power density from 0.84 GW/cm² to 5.29 GW/cm². And the residual stress obtains the minimum value -230 MPa at the laser power density of 3.06 GW/cm². With the increasing of spot diameter from 4 mm to 6 mm, the residual stress increased from -214 MPa to -30 MPa. With the increasing of laser pulse width from 10 ns to 40 ns, the residual stress decreased from -21 MPa to -288 MPa; and the depth of the compressive residual stress increased too. For all simulations under different LSP parameters, the minimum surface residual stress achieved at the bottom surface of the groove as well.

摘要

为了研究激光冲击强化后7050-T7451凹槽铝板残余应力场分布，测量了冲击后凹槽的残余应力分布规律：从凹槽中心到凹槽边缘，残余应力逐渐减小；在凹槽边缘底边处取最小值；然后沿凹槽边缘上升而增大，表面残余应力在凹槽曲面底边处取到最小值。采用ABAQUS有限元软件建立凹槽铝板的三维有限元模型，利用VDLOAD子程序施加载荷，进行数值分析得到了激光喷丸后残余应力分布并与试验测量结果对比，符合较好；然后研究了不同激光参数对凹槽铝板残余应力场的影响规律。结果表明：随着激光功率密度从0.84 GW/cm²增加到5.29 GW/cm²，残余应力先减小后增加，激光功率密度为3.06 GW/cm²时达到最小值-230 MPa；随着光斑直径从4 mm增加到6 mm，残余应力由-214 MPa增加至-30 MPa；随着激光脉宽从10 ns增加到40 ns，残余应力由-21 MPa减小至-288 MPa，残余压应力层深度逐渐增加；表面残余应力的最小值在凹槽曲面处取得。