超声滚压对激光选区熔化铝锂合金残余应力的影响模拟研究

Simulation Study on Effect of Ultrasonic Surface Rolling on Residual Stresses of Al-Li Alloy Fabricated by Selective Laser Melting

研究了铝锂合金试样激光选区熔化残余应力分布以及超声滚压对其应力场的影响。先后建立了单道扫描模型、试样模型以及超声滚压模型;分析了单道扫描模型的温度历史,并将此温度历史扩展至试样的沉积层,最终通过热力耦合与显示动力学分析获得激光选区熔化和超声滚压后的残余应力分布。结果表明,激光选区熔化试样顶部与四周出现了较大的残余拉应力;在超声滚压作用下,试样表层产生了高频振荡的应力场,并产生了较大的瞬时应力;试样表面残余拉应力转化为压应力,随着深度增加,残余压应力先增大后逐渐减小并逐渐转变为拉应力,最终恢复至激光选区熔化后的应力状态;模拟预测的结果与试验结果吻合较好,具有合理的精度。

The residual stress distribution and the effect of ultrasonic surface rolling(USR)on the stress field of Al-Li alloy by selective laser melting(SLM)are investigated.The single-channel scanning model,sample model and ultrasonic surface rolling model are established successively.The temperature history of the single-pass laser scan model is analyzed and extended to the sedimentary layer of the sample.The residual stress distributions after SLM and USR are obtained by thermodynamic coupling and display dynamics analysis.The results show that large residual tensile stresses appear around the surface and bottom of the specimen after SLM.Under the action of USR,a high-frequency oscillating stress field is generated in the surface layer of the specimen,and a large transient stress is generated.The residual tensile stress on the surface of the sample is transformed into compressive stress.With the increase of depth,the residual compressive stress first increases,then gradually decreases and becomes tensile stress,and finally returns to the stress state after SLM.The simulation predictions are in good agreement with the experimental results with reasonable accuracy.