搅拌摩擦焊接残余应力及残余变形数值分析

Investigations on residual stress and residual distortion of friction stir welding

建立了搅拌摩擦焊接顺序热力耦合有限元模型,用移动热源模拟搅拌头的作用,对搅拌摩擦焊接进行数值模拟.瞬态温度场及残余应力场与试验结果吻合良好,从而验证了该模型的正确性.本文研究了焊接过程中应力变化过程,指出应力场的不均匀分布引起板的弯曲变形.建立了不同尺寸有限元模型,研究板的尺寸对残余变形的影响.板的宽度对纵向残余变形曲率影响较大,长度对变形曲率影响较小。当焊接长度足够长,模型宽度相同时,不同模型远离端部区域纵向弯曲曲率相同.板的横向残余变形主要由焊缝区域变形引起,远离焊缝区域几乎没有弯曲变形发生,且板的尺寸对变形曲率影响很小.

Three dimensional sequential coupled thermal mechanical finite element(FE) models are established.And a moving heat source is introduced for the simulation of the moving welding tool.The temperature and the residual stress distribution agree well with the experimental observation that validates the FE model.The stress variation with time during friction stir welding(FSW) is studied,the uneven distribution of the stress causes the bending deformation.Nine models are established to investigate the effects of the model size on the residual distortion.The longitudinal bending curvature increases with increasing the length or decreasing the width.Compared with the length,the influence of the width is smaller.The longitudinal bending curvature is the same in the middle region of the welding line if the weld is long enough.The transverse distortion is mainly caused by the deformation of the heat affected zone and the bending curvature is not sensitive to the plate size.