Multiaxial Low Cycle Fatigue Life of Notched Specimen for Type 316L Stainless Steel under Non-Proportional Loading

Abstract

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 316L stainless steel. Four kinds of notched specimens were employed with elastic stress concentration factors, K t , as 1.5, 2.5, 4.2 and 6.0. The strain paths include proportional and non-proportional loadings. The former employed was a push-pull straining and a reversed torsion straining. The latter was achieved by strain path where axial and shear strains has 90° phase difference but their amplitudes are the same based on von Mises' criterion. The notch dependency of multiaxial low cycle fatigue life and the life estimation are discussed with employing inelastic finite element analysis. The lives depend on both K t and strain path. The strain parameter for the life estimation is discussed with the non-proportional strain parameter proposed by an author with introducing K t . The proposed parameter gave a satisfactory evaluation of multiaxial low cycle fatigue life for notched specimen of type 316L stainless steel under proportional and non-proportional loadings.

Influence of Notch Sensitivity and Crack Initiation Site on Low Cycle Fatigue Life of Notched Components under Multiaxial Non-proportional Loading

“…Crack initiation site was found to be shifted from the notch tip in 316LSS notched specimens analyzed in a previous study [46]. A successive study conducted on those specimens by Gallo et al [50] from a sophisticated FEM model, evidenced that the shift of the crack initiation site was caused by particular strain gradients.…”

“…In a previous work, the result of the application of I-S parameter on notched specimens has been compared with the data of smooth specimen, giving good results. [46,47,50]. However, the design phase requires a model that allows to calculate the number of cycles to failure.…”

“…Eq. (13) has been employed only for 316LSS stainless steel notched specimens [46,50]. In these studies, the results for notched specimens has been compared with data of smooth specimens.…”

“…Fatigue life was then correlated to the Itoh-Sakane parameter. AISI 316L notched specimens have been tested with non-proportional loading in a previous research [46,47]. The hardness of the specimens was firstly measured, and the fatigue life was estimated by using a modified Itoh-Sakane parameter.…”

Analysis of multiaxial low cycle fatigue of notched specimens for type 316L stainless steel under non-proportional loading

“…The results were successfully synthesized in a factor two band which suggested a good estimation of fatigue life and an accurate interpretation of the factors involved in the proposed model [28,29]. Recently, Itoh et al [30,31] The model is well supported by original finite element analyses that consider the cyclic stress and strain curves obtained experimentally. In detail, the specimen was modeled in different areas with different hardening levels.…”