Effect of surface energy on the plastic behavior of crystalline thin films under plane strain constrained shear

In this work, a new continuum dislocation based model for crystal plasticity with surface energy effect is proposed. Based on the model, a thin film under plane constrained shear is considered. From the perspective of energy, the yield strength as a function of film thickness has been calculated which is achieved by comparing the energy due to elastic deformation, plastic deformation without surface energy and that with surface energy effect. According to the numerical results, the model including the impenetrable surface assumption can capture the surface dominated deformation mechanism for thin films of nanometer scale. In addition, the transition in dominant deformation mechanisms is also predicted for film thicknesses ranging from tens of nanometers to several microns.