Simplified analysis method of complex piping systems in thermal-elastic-plastic-creep range

The elucidation of the behavior of piping system used in high temperature range is difficult because the plasticity and creep of materials are non-linear, but the accurate evaluation of this subject is indispensable for the safe design of piping system. Accordingly, the development of the simple and accurate analysis method has been studied. In this paper, the simplified method to clarify this problem is proposed. The finite element analysis for bent and straight pipes is based on the approximate constitutive relation formula unified in thermo-elasto-plastic creep range. The obtained numerical results have agreed well with the experimental and theoretical results obtained previously for simple piping models. Also, the elastic follow-up phenomena of actual complex piping system can be analyzed simply without much expense and labor. The constitutive formula, the formulation according to finite element method, the limit of application of this method, and the results of elastic analysis, elastoplastic analysis and elastoplastic creep analysis are reported. In this method, a straight pipe and a bent pipe are modeled with a straight beam and a curved beam, respectively, and the complementary energy in thermo-elasto-plastic creep range is used as the basis. (Kako, I.)