Impression creep of a viscous layer

Impression creep of a flat-ended cylindrical punch pushed into a viscous la yer overlaid on a rigid substrate is analyzed. The method developed here pe rmits us to relate the impression velocity to the punching stress in terms of an auxiliary function, which represents the solution of a set of Fredhol m integral equations with a continuous symmetrical kernel. By a series of n umerical analysis, the influence of the boundary conditions and the effect of the thickness of the layer on the impression velocity are obtained. For infinite thickness (i.e., h/a --> infinity, where h is the thickness of the layer and a is the radius of the punch), the impression creep is independe nt of the stick or slip boundary condition at the indenter/layer interface. For finite thickness such as h/a = 20, the boundary conditions have about 5% effect on the impression velocity. For a thin film, the impressing veloc ity is very sensitive to the boundary conditions. In fact it suggests a pos sible experimental way to detect debonding at the interface between the thi n film and the substrate.