A finite element model for spherical debris denting in heavily loaded contacts

The objective of this study is to develop models to investigate the effects of contaminants (debris denting process) in heavily loaded rolling and sliding contacts. A dynamic time dependent finite element model (FEM) was developed to determine the elastic-plastic deformation and contact force generated between the mating surfaces and a spherical debris as debris passes through the contact region. The FEA model was used to obtain the effects of various parameters such as debris sizes, material properties, friction coefficients, applied loads, and surface speeds on the elastic-plastic deformation and contact force of the system. The FEM was used to predict debris and mating surfaces deformations as a function of debris size, material properties, friction coefficient, applied load, and surface speed. Using the FEM, a parametric study demonstrated that material properties (i.e., modulus of elasticity, yield strength, ultimate strength and Poisson's ratio) and friction coefficients play significant roles on the height and width of dents on the mating surfaces. For lower friction coefficients (mu(d) < 0.3) the debris and mating surfaces slip more easily relative to one another and therefore the debris has lower aspect ratio. As friction coefficient is increased the debris and mating surfaces stick to one another and therefore the debris deforms less and has higher aspect ratio. The results indicate that the pressure generated between the debris and mating surfaces is high enough to plastically deform the debris and mating surfaces and cause a permanent dent on the surfaces and cause residual stresses around the dent. Based on the FEM results, a dry contact model (DCM) was developed to allow similar analyses as the FEM, however, in significantly shorter computational time.