2. Homogeneous deformation

2.1 Rheological models

For the homogeneous domain, the model currently most widely used in the literature is the so-called free volume model, which to a first approximation consists of the product of three terms: a defect concentration (or shear zones), a thermal activation term and a hyperbolic sine stress term, which derives from the bias introduced into the activation energy by the work of stress.

Historically, this form of stress-strain rate relationship was proposed by Spaepen in 1977