Low Cycle Fatigue Life Prediction of Notched Specimens Under Proportional and Non-proportional Multiaxial Loadings

Abstract

This study discusses multiaxial low cycle fatigue life of notched specimens under proportional and non-proportional loadings at room temperature. Strain controlled multiaxial low cycle fatigue tests were carried out using smooth and circumferentially notched round-bar specimens of two types of steels, SUS316 and SGV410. Two kinds of shallow notched specimens were employed of which elastic stress concentration factors, Kt, are 1.5 and 2.5. The strain paths include proportional and non-proportional loadings. The former employed a push-pull straining or a reversed torsion straining. The latter was achieved by strain path where axial and shear strains had 90 degree phase difference but their amplitudes were the same based on von Mises' criterion. The notch dependency of multiaxial low cycle fatigue life and the life predictability were discussed. The lives for both steels depend on both Kt and strain path. The data correlations also showed the different trend between the steels. The strain parameter for the life prediction was discussed with the non-proportional strain parameter proposed by one of the authors with introducing Kt. The proposed parameter gave a satisfactory correlation with multiaxial low cycle fatigue life of notched specimens for two steels under proportional and non-proportional loadings.