LOW CYCLE FATIGUE LIFE OF TYPE 316 STAINLESS STEEL NOTCHED SPECIMEN UNDER PROPORTIONAL AND NON-PROPORTIONAL MULTIAXIAL LOADINGS

This study discusses multiaxial low cycle fatigue life of notched specimen 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 type 316 stainless steel. Four kinds of notched specimens were employed of which elastic stress concentration factors, K-t, are 1.5, 2.5, 4.2 and 6.0. 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 has 90 degree phase difference but their amplitudes is the same based on von Mises' criterion. The notch dependency of multiaxial low cycle fatigue life and the life estimation are discussed. The lives depend on both K-t and strain path. The strain parameter for the life estimation is also discussed with the non-proportional strain parameter proposed by the author with introducing K-t. The proposed parameter gives a satisfactory correlation with multiaxial low cycle fatigue life of notched specimen of type 316 stainless steel under proportional and non-proportional loadings.