Development of a probabilistic model for the prediction of fatigue life in the very high cycle fatigue (VHCF) range based on inclusion population

Abstract

The aim of the present work is to develop a statistical approach for the correlation between the quality of metallic materials with respect to the size and arrangement of inclusions and fatigue life in the VHCF regime by using the example of an austenitic stainless steel of type AISI 304 containing martensite from predeformation. For this purpose, the size and location of about 60000 inclusions in cross sections of an AISI 304 sheet in both longitudinal and transversal direction were measured and subsequently modeled using conventional statistical functions. This way a statistical model of inclusion population in AISI 304 was created. The model forms a basis for the subsequent statistical prediction of inclusion distribution in fatigue specimens and the corresponding fatigue lives. The size and location distributions of the crack initiating inclusions were defined based on the modeled inclusion population and the stress distribution in the fatigue specimen, using the probabilistic Monte Carlo framework. The experimentally obtained information about the correlation between the size and location of the crack initiating inclusions and corresponding fatigue lives allows an assessment of fatigue life of the specimens corresponding to the modeled crack initiating inclusions. Reasonable agreement was obtained between modeling and experimental results.