Finite-element modeling and experimental comparisons of the effects of deformable ball indenters on Rockwell B hardness tests

Significant differences occur in Rockwell B hardness (HRB) tests depending on whether the 1.588 mm diameter ball indenter that is used is made of steel or of tungsten carbide (WC). It is important to study and assess the effect of different indenter materials on the HRB tests since the Rockwell hardness test method standards, published by ASTM International and the International Organization for Standardization, now permit the use of either steel or tungsten carbide ball indenters. In this paper, finite-element analysis (FEA) is used to simulate the HRB indentation process using steel and WC ball indenters on the same test materials under the same testing conditions. The influence of the deformable steel and WC indenters on the HRB tests is analyzed by comparing their FEA results with those of a simulated nondeformable rigid indenter. The contact pressure, stress, strain, and deformations of both the indenters and the tested materials during the loading and unloading period are analyzed. The FEA simulation results show that the HRB difference between steel and WC ball indenters is about 0.4 HRB for 40-78 HRB levels, but increases to 0.56 HRB at the 23 HRB level. The FEA simulation results agree with experimental HRB results.