Micromechanical study of the effect of inclusions on fatigue failure in a roller bearing

Abstract

Purpose – The purpose of this paper is to carry out a set of micromechanical analyses to study the effect of small inclusions on fatigue life of wind turbine bearings. Design/methodology/approach – The local stress concentrations around an inclusion are determined from a characteristic unit cell model containing a single inclusion, using the approximation of a 2D plane strain numerical analysis. The Dang Van multiaxial fatigue criterion is used for the local stresses in the matrix material, to ensure that the stresses remain within the fatigue limit. The matrix material is taken to be one of the most commonly used bearing steels, AISI 52100, and two different types of inclusions are considered. The macroscopic stress histories applied correspond to either a Hertzian or an elastohydrodynamic (EHL) contact pressure distribution under the rollers. Findings – The paper shows that sub-surface fatigue failure due to rolling contact is more likely to develop close to the inclusion-matrix interface, at particular angles that depend on the material and on the inclusion orientation. Originality/value – Inclusions represent an important issue in the design of wind turbine bearings, that are supposed to work in the very high cycle regime (N>109 cycles). This paper develops a micromechanical study that provides a deeper understanding on effect of inclusions on the fatigue life, according to one of the most used multiaxial fatigue criteria.