Cyclic viscoplastic behavior of thick spherical vessels under strain controlled loads based on the Chaboche unified model

Abstract

The purpose of this paper is to investigate the effect of stress classification on cyclic viscoplastic response of a structure (here, a thick spherical vessel which has an application in pressure vessel technology). The response is either reverse plasticity and shakedown or ratcheting behavior of a structure. The viscoplastic behavior of thick spherical vessels subjected to thermo-mechanical loads, using the rate-dependent Chaboche unified viscoplastic model with combined kinematic and isotropic hardening theory of plasticity, is evaluated. The material properties of the structure is assumed to be temperature dependent. A combination of generalized differential quadrature method (GDQ) and a precise numerical scheme, using the successive approximation iterative method, is employed to solve the resulting nonlinear differential equations. It is concluded that the Chaboche viscoplastic hardening model, as well as the plastic hardening model, predicts reverse plasticity under thermal cyclic loading with and without the creep consideration (a strain controlled cyclic loading). It is also shown that the rates of loading and unloading do not have significant influence on the cyclic viscoplastic behavior of the vessel, although they have influence on the strain and stress distributions.