Frictional stresses at the disc–jaw interface during the standardized execution of the Brazilian disc test

Abstract

An attempt to more accurately describe the boundary conditions of the standardized Brazilian disc test is presented. Specifically addressed is the problem of quantitatively relating the radial pressure with the tangential (frictional) stresses generated at the disc–jaw interface according to a physically acceptable law. A novel approach is proposed based on the notion that friction is directly related to the mismatch between the tangential components of displacement of the disc and jaw along their common interface due to the different deformability of the two materials. The surface displacements in both jaw and disc are determined using the complex potentials method, and the difference between their tangential components along the common contact arc is calculated. This difference in combination with the radial contact pressure tends to generate relative lateral displacements between the disc and jaw that are counterbalanced by frictional forces. The distribution of friction stresses along the contact rim obtained from the present approach fulfils all physical and intuitive imposed conditions. In addition, it is strongly skewed, attaining its maximum value at two-thirds distance from the centre of the contact arc, in good agreement with the earlier results based on a completely different approach.