Analysis of Knoop indentation strain hardening effects

Knoop indentation tests are a standard method for material characterization due to the fact that they provide an easy, inexpensive non-destructive and objective method of evaluating basic properties from small volumes of materials. The aim of this work is to explore the theoretical foundation of Knoop test and shed light to the interesting details that make the Knoop test so useful and simple. Our study builds upon the preliminary analyses of Knoop indentation by Giannakopoulos and Zisis (2011). We present a finite element study, in the frame of large elasto-plastic deformations, on the adhesionless contact of between a Knoop indenter and flat surfaces that exhibit strain hardening behavior. The material of the contacting solid is modeled as homogeneous and isotropic while frictionless contact conditions are assumed throughout. Results are presented for Linear-Power and Ramberg–Osgood laws of hardening behavior and compared with the elastic perfectly plastic case.