An elastic analysis of a heat exchanger piping using the finite element method

An elastic-plastic creep analysis based on the finite element method is performed to determine the structural response of a heat exchanger piping subjected to mechanical and thermal loading. The piping is comprised of a set of straight frame members. For the plastic analysis, the isotropic and Ziegler's kinematic hardening rules are employed. The creep law under uniaxial stress state is extended to give a generalized expression for multiaxial stress state. The combined strain-hardening and time-hardening procedure proposed by Cozzarelli and Shaw is adopted for the creep behavior under varying stress state. An incremental equilibrium equation is obtained using the virtual displacement principle. Element stiffness and nodal forces are calculated by numerical integration. The method to control the amount of increment is proposed since it highly influences the precision and the stability of calculations. Geometrical nonlinearity is considered to discuss the structural instability phenomena. A computer program, considering the above mentioned factors, is developed to analyse the creep buckling, ratchetting and other phenomena which are very important in the design of nuclear power plant components. The feasibility of this formulation is shown through several numerical examples. (Auth.)