A photoelastic study of the effect on subsurface stresses of the contact geometry and friction

Abstract

Three-dimensional photoelasticity has been used to investigate the effects of contact geometry and interfacial friction on the distribution of stress in a punch acting on a semi-infinite plate and a cup-cone contact. The analysis of the data was performed using an automated polariscope based on the method of phase stepping. The results show that the included half-angle of the punch has a significant effect on the magnitude of the stress which decreases with the angle. The effect of increasing the fillet radius is to lower the maximum subsurface shear stress. Reducing the inclination of the contact interface to the applied stress in the cup-cone model had the effect of raising the peak shear stress. By varying the interfacial friction no significant change in the subsurface stress was observed. It is demonstrated that the stress field around a crack is similar to that at the edge of contact and that the use of a normalized stress intensity factor is relevant to the stress field generated at the boundary of a contact. This parametric study has demonstrated that certain design parameters can reduce the local peak stresses around contact and therefore this would lead to a lower probability of crack initiation and propagation.