Nonconvex energy functions. Hemivariational inequalities and substationarity principles (Q793536)

The purpose of the paper is the derivation of certain variational principles for material laws and boundary conditions resulting from nonconvex, nondifferentiable potentials. Two recently defined concepts of generalized gradient of Clarke [\textit{F. H. Clarke,} Trans. Am. Math. Soc. 205, 247-262 (1975; Zbl 0307.26012)] and derivative container of Warga [\textit{J. Warga,} Calc. Var. Control Theory, Proc. Symp. Math. Res. Cent., Madison 1975, 13-46 (1976; Zbl 0355.26004)] are employed. Hemivariational inequalities corresponding to discussed problems are derived.