A New, Direct Approach Toward Modeling Rate-Dependent Fatigue Failure of Metals

Abstract

The main objective of this study is to propose a new finite $J_2-$flow elastoplastic model toward directly modeling metal fatigue behavior over the whole deformation range up to failure. A departure from usual elastoplastic models is that the concept of yielding is rendered irrelevant with a gradual, smooth transition from the elastic to the plastic state in a more realistic sense and, moreover, asymptotic loss of the strength is incorporated. It is demonstrated that the failure behavior may be derived as a direct consequence of the proposed model, without involving any additional failure criteria and any additional variables. Moreover, a direct and explicit approach is suggested to identify each rate-dependent parameter based on suitable test data. Results are presented for rate-dependent failure effects for both monotone and cyclic uniaxial tensile loadings from low to high strain rates. Model predictions compare well with test data.