Differentiation of energy functionals in the problem of a curvilinear crack in a plate with a possible contact of the crack faces

A problem of equilibrium of a cracked plate is considered within the framework of the Kirchhoff–Love model. Non-penetration conditions in the form of inequalities (Signorini-type conditions) are set on the crack faces. The behavior of the energy functional is studied for the case of a rather smooth perturbation of the domain of the general form. Sufficient conditions for the existence of the energy functional derivative with respect to the parameter of domain perturbation are derived.