Realistic constitutive relations for metal plasticity

The process of establishing quantitative constitutive relations is illustrated on the example of strain hardening: a phenomenological analysis in parallel with the derivation of physics-based combinations of variables; both followed by the use a sufficient set of experimental data to firm up unknown parameters or even unknown functions; and the eventual return to an assessment of the more detailed physical mechanisms that are suggested by the observed behavior. It is emphasized that a physics-based algebraic expansion around an accessible standard state is more reliable than a grand overall equation.