THIN-FILM DEFORMATION-BEHAVIOR OF POWER-LAW CREEPING MATERIALS

The behavior of power-law creeping materials in the form of thin films subject to plane strain and axisymmetric deformation is studied. Anal ytical 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 delaye d elasticity are discussed. Solutions are obtained for compression, sh ear, and combined compression with shear. The solutions provide a micr oscopic ''flat-plate'' viscous flow contact model for use in micromech anical models of particulates composites. It is concluded that for thi n films the elastic component of the material behavior can be modeled accurately using Nadia's solutions for an elastic material, and that t he nonlinear viscous component can be modeled well by assuming unidire ctional flow in a uniform passage. These two solutions can be combined into a nonlinear Maxwell model that describes the contact behavior ac curately, for small or large strains. Finally, the creep response of a plane-strain, power-law viscous contact under combined compression an d shear can be approximated by an elliptical function in terms of comp ressive and shear stresses or strain rates.