Plane problem of fracture mechanics for a hub of a friction pair is studied. It is suggested that near the rough friction surface, the hub has a rectilinear slot of variable width. The slot width is comparable with elastic deformations. A criterion and a method for solving the inverse problem of mechanics of contact fracture on definition of displacement function of the hub external contour points in a friction pair with regard to the temperature drop and irregularities of the contact surface in friction pair components is given.