E.N. Mamiya

Three-dimensional model for solids undergoing stress-induced phase transformations

Abstract A phenomenological model describing the mechanical behavior of polycrystalline solids undergoing stress-induced phase transformations is presented in the setting of three-dimensional (3-D) media. The model, which is developed within the framework of Generalized Standard Materials, has been built on a few basic assumptions, namely an admissibility condition for thermodynamic forces and a locking constraint for phase transformations. The macroscopic kinematic consequences of stress-induced phase transformations are described by a tensor named transformation strain. Numerical integrations of the resulting set of equations show that many features of shape memory alloys obtained by certain authors for CuAlZnMn alloys under non-proportional loadings can be qualitatively described by the present model.

Fatigue limit under multiaxial loadings: on the definition of the equivalent shear stress

Abstract The goal of the present paper is to propose a criterion to predict the fatigue strength of hard metals under conditions of multiaxial, non-proportional loadings. It is very simple to compute, but still provides very good results for a wide range of in-phase and out-of-phase cycling loads.

The application of a mesoscopic scale approach in fretting fatigue

This work concerns the application of a mesoscopic scale fatigue criterion to predict the initiation of cracks in components under fretting conditions. A verification of the analysis is carried out by considering available experimental data for fretting fatigue in a high strength Aluminium alloy commonly used in the aerospace industry. These experiments revealed there is a contact size effect in fretting fatigue life. The results show that the mesoscopic scale fatigue criterion can correctly predict the initiation of fretting cracks for larger contact configurations. It is concluded that the reason for the poor performance of the criterion in predicting failure at smaller contacts may well be related to the effect of the stress gradient, a variable not accounted for in the mesoscopic criterion here assessed.