Life assessment for metallic materials with the use of the strain criterion for low-cycle fatigue

In this paper the investigation results for verification of the developed low-cycle failure criterion as applied to multiaxial (non-proportional) loading are presented. Several approaches for determination of the parameter of sensitivity to the cycle non-proportionality are reviewed. Simple phenomenological models are proposed for determining the material parameters and constants of the criterion relationship. A method for describing Morrow’s cyclic diagrams using a material static stress–strain diagram and one base experiment under uniaxial cyclic loading on the limited number of cycles has been developed. For the verification of the proposed models and strain criterion life calculation of an aircraft structural element is executed. For this purpose FEM analysis, improvement of a nonlinear rule of damages accumulation and the concept of critical distance for determination of damage to a local concentrator zone was used. Conservative results of life forecasting which well correlate with experimental data are received.