Ratchet analysis of piping systems by dynamic elasto-plastic FEM

Ratchet is a phenomenon that local plastic strain accumulates when a highly pressurized piping system repeats yielding and unloading under cyclic loading such as bending and torsion. In this paper an elasto-plastic FE analysis program is developed for the dynamic design of piping systems in which ratchet is anticipated. For this purpose, geometrically nonlinear elasto-plastic solid elements are employed to model the part where ratchet may occur and the rest of the piping system is modeled by pipe elements. These two parts are combined each other by the penalty method. Through a numerical example it is demonstrated that ratchet is successfully simulated during the dynamic analysis of a piping system and it influences the dynamic response of the whole system. (author)