Analysis of Sliding Behaviour of Non-conformal Contacting Surfaces Subjected to Shear Traction

Abstract

Sliding behavior of the contacting surfaces of ball on flat plate surface under normal force and shear traction is studied in this work. A numerical approach that simulates the accumulation of stress in oscillating metal on metal contacts is proposed. The substrate material chosen for the analysis is ultra high strength steel, titanium alloy, magnesium alloy and aluminum alloy and the stainless steel material are considered for the rigid ball material. Before imposing sliding, the finite element model is subjected to various normal load in the range of 50-100N for four different materials considered in order to validate the model and also to evaluate the elastic-plastic condition of the pair. The finite element solution is validated through the Hertz solution for different contacting material pair under normal load. After the successful validation of the model, the sliding of amplitude 2mm with the velocity of 4mm/s is imposed on the finite element model. The analysis facilitates in evaluating the surface phenomena variables like contact stress distribution at the surface and sub-surface level, contact pressure, contact radius, shear stress and displacement. The tensile and the compressive stress values are obtained for the combined effect of normal load and shear traction and the same were normalized with the corresponding yield strength to determine the failure mode of the material surface. The magnitude of vonmises stress, shear stress and stress in sliding direction is found to be in higher magnitude when the sphere is at the end of the forward stroke. It is also observed that, tensile component of the shear stress is maximum when the traction is forward and the compressive shear stress is maximum when the traction is reverse. The maximum shear stress initially located at the sub-surface and travel towards the surface along with the movement of the ball. This tendency will propagate the cracks or defects from the sub-surface towards the surface. The results obtained from the analysis are exploited in the understanding of the tribological behavior of the contact pairs.