Thin Film Deformation Behavior of Power-Law Creeping Materials

Abstract

The behavior of power-law creeping materials in the form of thin films subject to plane strain and axisymmetric deformation is studied. Analytical calculations, finite-element analysis, and experimental studies are performed. Both the elastic and viscous behavior are investigated, and the effects of interfacial friction, compressibility, and delayed elasticity are discussed. Solutions are obtained for compression, shear, and combined compression with shear. The solutions provide a microscopic “flat-plate” viscous flow contact model for use in micromechanical models of particulates composites. It is concluded that for thin films the elastic component of the material behavior can be modeled accurately using Nadia's solutions for an elastic material, and that the nonlinear viscous component can be modeled well by assuming unidirectional flow in a uniform passage. These two solutions can be combined into a nonlinear Maxwell model that describes the contact behavior accurately, for small or large strains. Finally, the creep response of a plane-strain, power-law viscous contact under combined compression and shear can be approximated by an elliptical function in terms of compressive and shear stresses or strain rates.