Analysis On The Welding Thermal Field And Residual Stress Field Of Thick Plate By FEM

With many use of thick plate in modern industrial, the problem of residual stress inside the welded thick plate attracted much attention of researchers in the field. Due to the uneven heating and cooling during the welding process, the residual stress not only could lead to defects and deformation, but also had a significant harm for the safety of the component performance. So the study of the residual stress formation process and force distribution has a instructive significance of eliminating such residual stress.The study of residual stress can be divided into two fields: thermal field and residual stress field, the former is the basis of the latter. Because of the complexity of the welding process, the study for welding residual stress was mainly depend on the computer simulate. Although researchers have done a lot of research on welding residual stress of thin plate, they hadn’t considered the residual stress in thickness direction, just considered the distribution of the longitudinal residual stress and transverse residual stress on the surface of steel plate. In practice, more than 40 mm thick plate are used in the actual project, so we must be care of the research on residual stress in thickness direction of steel plate but can’t ignore it.A 60 mm Q345A rigid thick plate was modeled in order to simulate the welding residual stress by finite element simulation software ANSYS, both double ellipse heat source model and element birth and death technique were introduced to simulate the welding process. The author succeed to write out the APDL command flow about the welding thermal field and residual stress of thick steel plate by the series of simplification and assumption, the material properties change was nonlinear when considered temperature change. Finally, the thermal field distribution and residual stress field distribution were obtained. The thermal field stress nephogram shows that the shape of thermal field like a spindle during welding period and the tail area turns longer, the temperature of ahead welding heat source is too high but the temperature of behind welding heat source is much higher than the behind; There are different initial temperature between the weld seam in multilayer multi-channel welding, and the initial temperature in latter layer is higher than the former layer; Once the temperature cooling to 67℃, the residual stress has been formed. The residual stress curve shows that the longitudinal residual stress is more than 403 Mpa, which is exceed the material yield limit, moreover, the distribution is symmetrical. The lateral residual stress is approximating parabolic distribution, the comprehensive stress is appeared near the weld seam and the tensile stress is appeared far away the weld seam. The residual stress of thickness direction is far less than the lateral and longitudinal residua stress, the stress value is fluctuations in zero. At last, the conclusion of this article has a considerable influence on the follow-up research work,and provided some suggestive guidance for the further research.