極厚板多層突合せ溶接残留応力分布とその生成機構特性に基づく理論解析及び実験の簡略化

抄録

Information about welding transient and residual stresses produced in welded joints is indispensable to investigate weld cracking and the safety of welded structures. Such information can be obtained either from a theoretical analysis or an experiment. Nevertheless, for estimation of welding residual stresses in a very thick plate produced by multipass welding, the analysis takes a long computation time and the experiment requires much labor.
The aim of this research is to contrive an analysis method in order to accurately estimate such welding residual stresses in much shorter computation time and with far less labor than ever. It is the theory of thermal elastic-plastic analysis based on the finite element method that is always adopted as the analytical theory. Applying this theory to the analysis of transient and residual stresses due to multipass welding, the analysis method (specimen, mesh division, analytical procedure, etc.) is simplified. This analysis method excluding the analytiacl theory is hereinafter called the analytical model. Applying the same theory of thermal elastic-plastic analysis to this analytical model which is as accurate as possible, a theoretical analysis is performed. From the result of this analysis, the production mechanism and the distribution of the above mentioned residual stresses are investigated in detail. Based on these results, the analytical model is simplified to accurately estimate (1) the distributions of transient and residual stresses in the whole cross section and (2) the distribution of residual stresses only near the finishing bead (in this vicinity, maximum tensile residual stresses are generally produced and such weld cracks as longitudinal ones and transverse onse may occur).
It is shown that highly accurate solutions can be obtained by the proposed simplified analytical models in a very short computation time. It is also shown that the experiment can be similarly simplified, which is very effective especially for residual stresses near the finishing bead.