Study Of The Distribution Of Residual Stress In Thick Plate Butt Welding

Thick plates in large-scale steel structures and piping engineering projects are often connected by welding, due to the high concentration of transient heat input in the welding process, so there will produce a large residual stress and residual deformation during and after the welding. The welding residual stress will seriously affect the using performance of the structures, and meanwhile, it is affected by many factors and varied complicatedly, therefore, the research of thick plates welding residual stress has a very important practical significance.In this paper, two plates with thickness of 100mm were presented, which are made of A105 steel, subjected to a narrow-gap U-groove and multi-pass weld with submerged automatic arc welding technology.This paper began with the experiment at first, using X-350AL X-ray stress measuring instrument to survey the welding residual stress on the surface. The measuring points were arranged on the non-equidistant lines in biaxial plane. And then some distribution curves of residual stress were submitted after analyzing the measuring data, from which, some distribution rules were given at the same time.Followed by that, WELD PATH in the general-purpose finite element calculation software MSC.Marc2007 was used to define the welding path, to simulate the welding process and to calculate. The calculation results and measuring results show good agreement between the two, proving the validity of the finite element method. The residual stress in thickness direction can be derived from the calculation results after the verification of the surface residual stress, which can solve the problem of getting stress values in thick direction easily.Finally, for the distribution rule of residual stress along the weld direction, the weld vertical direction andσz along the thickness direction, some distribution curves were fitted based on the Levenberg-Marquardt method and general global optimization algorithm, and then some fitting equations were given. Furthermore, after the analysis of the distribution of two-dimensional curved surface, two-dimensional distribution model for residual stress was offered.The established finite element model and the proposed mathematical distribution model of residual stress in this article will provide guidance for the actual welding and offer reference for the future research work.