Studies on Thermal Elasto-Plastic Problems (4th Report)

Abstract

The residual stress due to circumferential welds in cylindrical shells is one of the most important problems concerning stress corrosion cracking in piping structures in service. Recently in Japan, many researches are carried out with regard to the above problems.It is well known that the state of stress in welded cylinder may be quite different from that in butt welds of flat plates. This is because not only hoop stress but also bending stress in the axial direction is produced. This bending stress is induced because radial displacement caused by circumferential shrinkage occurs.In this paper, one dimensional thermal elasto-plastic analysis using Rayleigh-Ritz method is applied to the axi-symmetric thermal stress problems of thin cylindrical shells. The adoption of deflection function which satisfies the geometrical boundary condition yields more accurate solution compared with that of FEM even in case of smaller degree of freedom.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 cylindrical shells and welding heat input on welding deflections and residual stresses is clarified. This influence is described by the use of parameter (Q/h) ·β. The estimation chart of deflections and residual stresses for a given cylindrical shell is also presented.