Figure shows the dependence of the TCP decomposition rate on shear stress for iron, iron carbide, and iron oxide surfaces. The decomposition rates were determined from the exponential decay fits shown in Figure and the shear stress values were taken from Figure . The TCP decomposition rate increases exponentially with shear stress and also with temperature, suggesting that these reactions are stress-augmented thermally activated (SATA) processes. The Bell model 95 can be used to describe the kinetics of SATA processes, and the rate constant, k, can be calculated as: