Analysis of elastoplastic response in FGH97 notched specimens based on viscoplastic constitutive model

In order to solve the difficulties in measuring local stress and strain, the parameters of Chaboche viscoplastic constitutive equations for powder metallurgy super alloy FGH97 at 550 °C, which were obtained based on the experiments of material mechanical properties, were used in the elastoplastic FEM (finite element method) analysis of notched specimens subjected to tensile and cyclic loading. The results show that: (1) plastic stress/strain state at notch root is obviously different from elastic one. With the increase of stress, location of maximum stress moves inside. (2) Under cyclic loading, with the increase of cyclic number, the stress and strain range along symmetric path at notch root changes little. Mean stress relaxation occured in the plastic zone at notch root gradually turns to be stable, and it also leads to different cyclic stress ratios compared with the applied load. (3) The plastic zone at notch root gradually increases, but the increasing range gradually decreases. The research result can provide support to further analysis of influencing factors which affect fatigue life of FGH97 notched specimens.