Analysis of Ultramicrohardness by Conical Indenter : 1st Report, Analysis of Indentation Process Using FEM and Correction of Indenter Tip Radius

Abstract

Deformation around a concavity created by indentation of a conical indenter in an ultramicrohardness tester is analyzed using FEM computer simulation. Effects of indenter tip radius, work hardening in material and indenter shape on concavity shape and hardness from concavity depth both under loading and load-free conditions are examined. The results obtained are as follows. (1) Concavity in high work hardening material is of the sinking in type including concavity rim. On the other hand concavity in low work hardening material is of the piling-up type in which the rim rises above the material surface. Existence of indenter tip radius makes the inclination marked. (2) The lower the work hardening of material is, the broader the plastic zone around the concavity created by a conical indenter spreads parallel to the surface and the higher the peak value of the plastlc strain near the tip of the indenter. Existence of indenter tip radius makes the plastic zone large and the peak value of the plastic strain around the bottom of concavity small. (3) Indenter shape influences concavity shape. However there is almost no difference in the depth of plastic zone. (4) Correction of errors at the indenter tip, which is effective to Vickers and triangular pyramid indenters, can be applied to a conical indenter.