A CFD-FEM based partitioned fluid structure interaction model to investigate surface cracks in elastohydrodynamic lubricated line contacts

Abstract

This paper presents a partitioned, two-dimensional fluid structure interaction (FSI) model developed to investigate the effects of surface cracks in rolling/sliding line contacts operating under elastohydrodynamic lubrication (EHL). The lubricant behavior as it flows over and through the crack is determined by solving the Navier-Stokes equations using the Ansys Fluent computational fluid dynamics (CFD) solver. The structural response of the solid body is governed via an elastic-plastic constitutive relationship and solved using the Ansys Mechanical finite element solver. The exchange of (i) forces due to fluid pressure, and (ii) displacements due to solid deformation across the fluid-solid interface (including the crack faces) is facilitated by an iterative implicit coupling scheme. A smoothing based dynamic meshing technique is utilized to capture the deformation of the fluid region. The FSI model developed for this investigation is capable of modeling surface cracks with inclined geometries, overcoming the limitations of the classical Reynolds based approach. The fluid pressure results are presented for different loads, speeds and slide-to-roll ratios. The effects of crack geometry (i.e. location, dimension, inclination, crack tip radius, etc.) on fluid pressure and structural response are investigated. The FSI model presents the details of pressure distribution, fluid streamlines and stress concentration in the solid simultaneously. The model results can be used to provide accurate boundary conditions on the crack faces for crack propagation modeling in rolling contact fatigue. The results of this investigation identify the crack geometries that affect fatigue life of rolling elements in EHL contact by predicting the location and severity of stress concentrations in the material.