初始应力对三维光学轮廓法测试焊接接头残余应力的影响

目的研究不同初始应力状态下,三维光学轮廓法测试焊接接头残余应力的变化规律。方法采用MIG焊分别对供货态与去应力退火态试板进行多层多道焊,焊后试板经慢走丝切割,经三维光学测量技术扫描切割面轮廓,将所得轮廓数据经所建立的数据处理平台处理,将其结果作为有限元计算的边界条件,经应力反算得到残余应力分布。最后再进行有限元模拟,计算焊接接头残余应力。结果含初始应力、去应力退火和数值模拟的焊缝中心均为拉应力区,最大拉应力分别为480, 450, 523 MPa,且都位于焊缝根部区域。三者试板两侧为压应力区域,最大压应力分别为380, 280, 157 MPa,三者数值相差较大。结论将含有初始残余应力试板、退火处理试板与数值模拟结果的残余应力分布进行对比,可以发现三者在焊缝中心处的残余应力分布较为一致,但沿着焊缝向两侧的区域内,应力差别逐渐变大。主要原因为焊接热循环温度高于金属再结晶温度时可以消除部分残余应力,而温度循环较低时对应力消除不明显,导致实验结果相差较大。

Effects of Initial Stress on Residual Stress of Welded Joints Tested by Three-Dimensional Optical Contour Method

The paper aims to research the variation of residual stress in welded joints tested by 3D optical contour method under different initial stress states. MIG welding was used to perform multi-layer and multi-pass welding on the as-supplied and unstressed annealed test plates. After welding, the test plates were cut by slow wire cutting, and the contours of the cut surface were scanned with 3D optical measurement technology. The data processing platform was used to process, and the results were used as the boundary conditions for the finite element calculation. The residual stress distribution was obtained by back-calculating the stress. Finally, a finite element simulation was performed to calculate the residual stress of the welded joint. The centers of the weld containing initial stress, stress relief annealing and numerical simulation were in the tensile stress zone. The maximum tensile stress was 480, 450, 523 MPa, and they were all located in the root region of the weld. The two sides of the three test plates were the compressive stress areas, and the maximum compressive stress was 380, 280, 157 MPa, respectively. By comparing the residual stress distribution of the initial residual stress test panel, the annealed test panel and the numerical simulation results, it can be found that the residual stress distribution of the three at the center of the weld is more consistent; while the stress difference gradually becomes larger in the area along the weld to the two sides. The main reason is that part of the residual stress can be eliminated when the welding thermal cycle temperature is higher than the metal recrystallization temperature, and the stress relief is not obvious when the temperature cycle is lower, which results in a large difference in experimental results.