Unique solvability of crack problem with time-dependent friction condition in linearized elastodynamic body

This study considers a crack problem with a time-dependent friction condition in a linearized elastodynamic body. We suppose that the crack is fixed and the frictional force acting on the crack is given and depends on the time as well as space variables. The problem is then reduced to a variational inequality of the hyperbolic type. The unique existence of a solution is proved by using Galerkin's method and deriving a priori estimates for the penalized problem.