基于固有应变法的激光增材制造特征结构应力与变形高效预测  

Effect Prediction of Stress and Deformation for Laser Additive Manufacturing of Characteristic Structure Based on Inherent Strain Method

作　　者：尹清远 韦辉亮 张昌春 刘婷婷[1] 廖文和[1] Yin Qingyuan;Wei Huiliang;Zhang Changchun;Liu Tingting;Liao Wenhe(School of Mechanical Engineering,Nanjing University of Science and Technology,Nanjing 210094,Jiangsu,China)

机构地区：[1]南京理工大学机械工程学院,江苏南京210094

出　　处：《中国激光》2022年第14期151-165,共15页Chinese Journal of Lasers

基　　金：国家自然科学基金(52175330);江苏省自然科学基金(BK20202007);中央高校基本科研业务费专项资金(30921011202)。

摘　　要：在激光粉末床熔融过程中,热循环和热积累导致零件产生残余应力和变形,对零件的成形精度带来极大的影响。由于计算量过大,利用热弹塑性模型难以实现尺寸较大的结构残余应力和变形的模拟。为了实现快速准确的预测,基于改进的固有应变理论,从热弹塑性模型中提取固有应变矢量并逐层施加至典型特征结构中,系统性地研究了四种扫描策略下特征结构的残余应力和变形分布。研究发现,在不同扫描策略下,薄壁结构、悬臂梁和悬垂圆孔结构表现出相同的变形趋势,即扫描方向沿短边时变形最小。其原因一为扫描方向沿短边方向时扫描矢量长度较小,二为相同应力下短边变形小于长边变形,从而产生小的残余应力及变形。对悬垂结构增加支撑有利于减小翘曲变形,提高成形质量。在悬垂圆孔结构外侧,随打印高度逐渐增大的竖直方向的拉应力是影响其变形的主要原因。所得结果可对获得低应力、高精度增材制造结构以及提高增材制造成形质量提供有效技术支撑。Objective During laser powder bed fusion(PBF),the complex thermal cycles and intensive heat accumulation may lead to serious residual stress and deformation,which have a great impact on the forming accuracy of parts.For parts with characteristic structures such as thin-walled structures and cantilever beams,various scanning strategies can cause different residual stresses and deformations.Thus,it is important to study the influence of printing parameters on the characteristic structures to improve forming accuracy.Numerical simulation can be used to well predict the residual stress and deformation of characteristic structures in order to enhance the data integrity and further avoid the deficiencies of experimental measurements.However,it is difficult to simulate the residual stress and deformation of large-scale structures by using the thermal-elastic-plastic model due to the high computational cost.In this work,the inherent strain method is adopted to achieve a fast and accurate prediction of residual stress and deformation,which is based on the improved intrinsic strain theory for different characteristic structures under four scanning strategies.Methods In order to achieve an efficient and accurate prediction of residual stress and deformation of characteristic structures,the modified inherent strain method is used for simulation.The thermal-elastic-plastic model is first established using the ABAQUS software to simulate the temperature and stress fields during the two-layer laser PBF of Ti-6Al-4V for the 0°line scanning strategy.Subsequently,the elastic and plastic strain vectors of multiple points along the scanning path are extracted.The inherent strain vector of each point and the averaged inherent strain vector for the 0°line scanning strategy are finally calculated.The inherent strain vector for the scanning strategy along the 0°direction without rotation between layers is obtained via averaging the inherent strain vector of each point.Moreover,the inherent strain vector for the 90°rotation scanning

关 键 词：激光技术 激光粉末床熔融 固有应变 特征结构 扫描策略 变形预测 

分 类 号：TF124[冶金工程—粉末冶金]