13. A Research on Welding Deformation of Spherical Shell Structures

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Welding deformations and residual stresses are major factors which affect the collapse strength of externally pressurized vessels. Problems of circumferentially welded cylindrical shells and spherical shells welded along the equators have been investigated by the authors. In many cases, penetrators or partial spheres are welded circumferentially to spherical shells in actual structures. In these cases, a part of the spherical shell near the weld line and the penetrator tend to deform inward. In this report, the deformations of a spherical shell caused by the welding of a penetrator or partial sphere are investigated. Experiments were carried out in order to clarify the characteristics of welding deformations and the effects of dimensions of shell and penetrator and welding procedures on the deformation. One dimensional thermal elasto-plastic analysis using Rayleigh-Ritz method is applied to the axi-symmetric thermal stress problems of this spherical shells. The results obtained in this research are as follows; The deformation in a spherical shell is mainly caused by thermal shrinkage. Its profile resembles to that in butt-welded cylindrical shell or spherical shell welded along the equator. The effectiveness of this analytical method and reliability of its results are confirmed by comparison with experimental results. The influence of size of spherical shells and penetrators and welding heat input on welding deflections and residual stresses is discussed. It was known that the parameter λ and λα, correlating the rigidity of shell and the size of penetrator, and the parameter (Q/h)β of heat input, are governing the welding deflections. The deflection caused by the welding of penetrator shows the maximum value when the size of penetrator λα equals 0.7〜1.3, and this value is three times large as that by the welding along the equator, and when the size of penetrator λα is larger than 4.0〜5.0, the welding deflection is almost the same as that by the welding along the equator.
社団法人日本船舶海洋工学会の論文

13. A Research on Welding Deformation of Spherical Shell Structures

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