Research on Welding Deformations of Spherical Shell Structure (2 nd report)

Abstract

Welding deformations and residual stresses are major factors which affect the collapse strength of externally pressurized vessels. Problems of circumferentially welded cylindrical shell and spherical shell welded along the equator have been already investigated by some of the authors.There are many cases that a penetrator or a partial sphere is welded circumferentially to a spherical shell in actual structures. In this case, the spherical shell near the weld line and the penetrator tend to sink toward the center of spherical shell.In the previous paper, the deformations of a spherical shell caused by the welding of penetrator were investigated. Experiments were carried out in order to clarify the characteristics of welding deformations and the effects of shell and penetrator dimensions and welding procedures on them.In this paper, one dimensional thermal elasto-plastic analysis using Rayleigh-Ritz method is applied to the axi-symmetric thermal stress problems of thin spherical shells. The following conclusions are obtained from this analysis. The effectiveness of this analytical method and reliability of its results are confirmed by comparison with the experimental results. The influence of size of spherical shells and penetrators and welding heat input on welding deflections and residual stresses is described. It is clarified that the parameter λ and λα, which correlate the rigidity of shell and the size of penetrator, and the parameter (Q/h) β, which correlates welding thermal cycle, are effective to estimate the welding deflections. The deflection caused by the welding of penetrator shows maximum value when the size of penetrator λαequals 0. 71. 3, and this value is three times as large as that by the welding along the equator, and as the size of penetrator λα is larger than 4. 05. O, the welding deflection is almost the same as that by the welding along the equator.