Effect of the residual stress on contact fatigue of a wind turbine carburized gear with multiaxial fatigue criteria

Abstract

Carburized gears are extensively applied in heavy duty machines such as wind turbines. The variations of hardness and residual stress introduced by carburizing and quenching processes remarkably affect the rolling contact fatigue (RCF) during repeated gear meshing. The present work attempts to study the effect of the residual stress on rolling contact fatigue and predict the rolling contact fatigue life of a wind turbine carburized gear based on multiaxial fatigue criteria. A finite element elastic-plastic contact model is developed which takes the gradients of hardness and initial residual stress into account. Initial residual stress distribution is obtained through experimental measurements. The stabilized stress strain field is carried out by considering the shakedown state under the heavy load conditions. The Fatemi–Socie and the Brown–Miller criteria are used to estimate the contact fatigue damage of the carburized gear. Numerical results reveal that the effect of the initial residual stress on the contact fatigue failure can be reflected by the Fatemi–Socie criterion whereas it is not reflected by the Brown–Miller criterion since the two strain parameters appeared in the criterion are not influenced by residual stress. In terms of the Fatemi-Socie criterion, under modest load conditions where elastic response occur, a considerable compressive residual stress would alter the plane orientations of crack initiation, while under extremely heavy load conditions where plasticity occur, the influence of the initial residual stress on contact fatigue damage is limited within the near-surface non-plastic zone. The effect of the initial residual stress on contact fatigue life represents a bilinear curve. As the magnitude of the tensile residual stress increases, the RCF life decreases linearly. As the magnitude of the compressive residual stress exceeds a certain value, the RCF life does not increase anymore.