Numerical Simulation Of Welding Residual Stress And Deformation Of The Excavator Boom

Boom is a major excavator welded structure, severe non-uniform heating and cooling will produce residual deformation and residual stress, which is not negligible, in the welding process. Welding residual stress and deformation seriously affect the accuracy of the structural design and structure reasonable reliability. Therefore, scientific, systematic and quantitative prediction and control of residual deformation and residual stress is particularly important.Based on the sectional theory, the segmented moving temperature-controlled volume heat source model was proposed by using weld equivalent temperature as control variables, and it was verified through Q345 B flat butt welding simulation model. With calculation time and accuracy as a reference, based on different mesh sizes, computing efficiency was compared of the three kinds of heat source models including the segmented moving temperature-controlled heat source model, the double ellipsoid heat source model and the segmented moving double ellipsoid heat source model. The results shown that the trend of residual stress and deformation of the proposed model was consistent with that of the moving double ellipsoid heat resource model, and its accuracy was similar to that of the segmented moving double ellipsoid heat source model, but the calculation time is shorter. Particularly, the effect was more prominent on the large and complex structures.The segmented moving combined welding heat source model is proposed using thermal cycle curve as control variables. With shape characteristic of molten pool as research object, temperature field of cross section is compared of the four kinds of heat source models including the combined welding heat source model, the segmentedmoving combined welding heat source model(constant type), the segmented moving combined welding heat source model(variable type), and the segmented moving thermal cycle curve controlled and combined welding heat source model. The results showed that the geometry of the temperature field of the proposed model is consistent with that of the results of physical experiments, and more computationally efficient than other heat source models.Through the thermal elastic-plastic finite element method, according to two welding program, welding residual distortion and residual strain of excavator boom was successfully predicted by the segmented moving combined welding heat source model as welding model and adopting a series measures, which have high calculation precision. Compared simulation results with measurement results, the results showed that according to two kinds of welding program, there is a big difference between the displacement curve key size, but the amount of residual deformation similar, the residual deformation has a contraction in the vertical direction, the front stretch and the rear compression in the horizontal direction, the overall presence of warpage, which is in accordance with the measurement results. Distribution of residual stress is approximately the same under the two programs, but the area of dangerous stress zone smaller, peak stress smaller and less overall stress gradients in Option II.