  We propose an approach to describe the propagation of a crack (or boundary of
an adhesive contact) in a viscoelastic material which is only based on the
consideration of the rheology of the material without the introduction of any
additional dependency of the separation energy on the velocity of crack
propagation. The suggested idea is illustrated with an example of kinetics of
detachment of a flat-ended indenter from a viscoelastic medium. It is shown
that under the given assumptions the crack propagation is accelerating until
the critical configuration is reached and the contact detaches instantaneously.
The suggested criterion can be basically applied to arbitrary shapes and
arbitrary loading histories.
