Author(s)

F. Wredenberg & P.-L. Larsson

Abstract

A numerical strategy for analysis of the scratch test is presented and verified by experiments. The material is described by standard von Mises plasticity with strain hardening effects utilizing large deformation theory.A parametric study with respect to the well known Johnson’s parameter, often used to correlate indentation experiments, was performed numerically and the existence of a representative strain describing important scratch quantities was investigated. The influence of internal friction was also studied. Keywords: scratch test, hardness, friction, finite elements, contact. 1 Introduction Scratch testing and standard indentation show many similar features. Indentation hardness has been used extensively to characterizematerials. The indentation hardness is defined as H = P A , (1) where P is the force on the indenter normal to the specimen surface and A is the normally projected contact area. Johnson [1] recognizes that the indentation hardness, at classical elasto-plastic material behavior, follows a master curve (figure 1) dependent only on a rheological parameter Λ (see eqn (2)). Λ is also known as Johnson’s parameter and defined according to Λ = E 1 − ν2 tan β σ(repr) . (2) In eqn (2) β is the indenter angle (see figure 2), E the elastic modulus, ν the Poisson’s ratio and σ(repr) the flow stress at a representative effective plastic strain

Keywords

scratch test, hardness, friction, finite elements, contact.