Y. Dumont, D. Goeleven, K. Kuttler, M. Rochdi and M. Shillor,
J. Math. Anal. Appl., 247(1)(2000), 87-109.

Dynamic frictional contact with adhesion of a viscoelastic body and a
foundation is formulated as a hemivariational inequality. This may model
the dynamics of rock layers. The normal stress-displacement relation on
the contact boundary is nonmonotone and nonconvex because of the adhesion
process. A sequence of regularized problems is considered, the necessary a
priori estimates obtained and the existence of a weak solution for the
hemivariational inequality is established by passing to the limit as the
regularization parameter vanishes.