## Constitutive Laws: Plasticity

The constitutive model describing metal plasticity is considered one of the earliest nonelastic nonlinear constitutive models that describe the complex relationship between the stress and the strain exhibited in metals. The roots of the theory stem back to the end of the nineteenth century with the work of various researchers on the behaviour of metals under loading. Many of the current concepts of yielding and plastic behaviour date back to the 1950’s when the theory of plasticity was formally organized by Rodney Hill in his classical book: “The Mathematical Theory of Plasticity” which was first published in 1950 and has been republished several times since then.

In this section, the physical behaviour of metals will be described along with the theoretical model that aims to mimic the physical observations.