The plasticity region is at the top of deformation map (at the highest normalized stresses), and is below the boundary set by the ideal strength. In this region the strain rate involves an exponential term. This equation is shown below, where  is the applied shear stress,  is the shear modulus,  is the energy barrier to dislocation glide, k is the Boltzmann constant, and  is the "athermal flow strength" which is a function of the obstacles to dislocation glide.