数值模拟和实验研究Ti6Al4V合金激光熔透焊接残余应力

Numerical and Experimental Analysis of Residual Stresses in Full-Penetration Laser Beam Welding of Ti6Al4V Alloy

摘要:

采用热-弹塑性三维有限元法研究激光熔透焊接Ti6Al4V合金的残余应力，并采用小孔法测量焊接残余应力以和计算结果进行比较。有限元计算时，建立了以焊缝形貌尺寸为参数的统一锥形热源模型来模拟不同热输入时的焊接温度场，并讨论了边界条件和有限元网格大小的确定。研究结果表明：采用焊缝轮廓尺寸作为热源参数能准确模拟焊缝横截面轮廓；钛合金激光熔透焊接的纵向残余应力分布梯度陡；在焊件表面和内部残余应力分布趋势不同，采用小孔法测量的残余应力分布和计算的焊接件内部残余应力分布相似。

Abstract:

A 3D thermal elastic-plastic finite element model to predict welding residual stresses induced by full-penetration laser welding of Ti6Al4V alloy was described in detail. The welding experiments and residual stresses measurements by through-thickness hole-drilling method were also performed to validate the simulated results. A uniform conical heat source model with parameters taken from the actual weld seam dimensions was developed to simulate the welding temperature fields with different welding heat inputs. The thermal elastic-plastic finite element simulation was employed to calculate the welding residual stresses. The boundary conditions and the size of finite element mesh were also discussed. The results show that the cross section profiles of the weld seam simulated with the conical heat source based on the configuration of weld seam agree well with the experimental results; the zone of residual stresses distribution in laser full-penetration welding of Ti6Al4V alloy is very narrow and the gradient of longitudinal residual stress is very steep; the residual stresses distribution on the surfaces are different from those in the interior of the welding seam; the measured residual stresses by through-thickness hole-drilling method are similar to the simulated ones in the interior of the welding seam.