Strain Rate Gradient Model with Couple Stress for Micro Scale Rigid-Viscosity-Plastic Deformation
In order to describe scale effects in rigid-viscosity-plastic deformation at micro scale, a strain rate gradient model with couple stress is proposed. In the constitutive equation, couple stress, strain rate gradient are introduced on the assumption that the potential energy depends upon the scalar invariants of the strain rate tensor and strain rate gradient tensor, at the same times, the influences of length scale of body, grain size and temperature are also considered. A FEM-based program based on this strain rate gradient model is used to simulate the process of high temperature gas pressure forming, and the value of length scale 2 l is evaluated by simulation pilot calculation. It is indicated that rigid-viscosity-plastic deformation can be more accurately simulated by the present strain gradient rate model as long as the material parameters in constitutive equation are selected suitably.
K. Lei and K. F. Zhang, "Strain Rate Gradient Model with Couple Stress for Micro Scale Rigid-Viscosity-Plastic Deformation", Materials Science Forum, Vols. 551-552, pp. 323-328, 2007