Modelling of cracking in circular disk loaded by concentrated forces

An isotropic disk of radius $R$, loaded on the contour by two concentrated forces $P$, apllied to the points $z_1=R$ and $z_2=-R$, is considered. A model of cracking in a circular disk, based on consideration of fracture process zone, is proposed. It is assumed that the fracture process zone is a finite length layer, containing material with partially broken bonds between individual structural elements. Equations for determination of the external load critical value at which the crack is observed are obtained.