On the simulation of microhardness at large strains using a gradient theory of plasticity

摘要

Indentations tests, e.g. the Brinell and Vickers tests, are frequently exploited to evaluate the hardness of metals, which reflects the elastic as well as the plastic properties. It is a well-known fact that the hardness shows significant size-effect when the diameter of the indenter is of the order of one micron in the context of engineering metals. In this contribution we employ a recently developed gradient theory of macroscopic plasticity in order to evaluate such microhardness. The proposed gradient theory is thermodynamically consistent and is valid for large inelastic strains (as well as large elastic strains; however the elastic strain remains small in the present application), cf (Svedberg, 2000). Finite element simulations demonstrate the size-effect on the hardness for different head-shapes of the indenter.