Boundary condition considering shear force applied on flat loading platen for brazilian test

Abstract

In general, the method used to obtain the tensile strength from a Brazilian test depends on the elastic theory for a pair of concentrated forces. However, the contact areas between the specimen and loading platens are observed in experiments. Several attempts have been tried for the boundary conditions in modeling of an isotropic or orthotropic circular disk in the Brazilian test. The forces in only the normal direction to the loading platen or specimen have been dealt with in most of these models. Therefore, a dent in the contact area between specimen and loading platens is observed in numerical results from most models. However, no dents have ever been observed in experiments using loading platens. In this study, not only normal loads but also shear loads on the loading platens are adopted as boundary conditions. The depth of the resulting dent from the present model is smaller than those seen in previous studies. In addition, huge tensile stresses are observed near both edges of the contact area in the present model. Furthermore, cracks are also observed near both edges in experiments. In brittle materials, cracks are caused by tensile stress. Therefore, the accuracy of calculations is expected to be improved using the present model for Brazilian tests.