A work approach to determine vickers indentation fracture toughness

According to the comparison of Vickers microindentation tests and Vickers macroindentation tests on several brittle materials, it is found that the ratio of hardness (H) to elastic modulus (E) is sensitive to well-developed radial cracks, but the ratio of unloading work (W_u) to total loading work (W_t) is not. Based on this finding together with the approximate linear relationship between the ratio of H to reduced modulus (E_r) and W_u/W_t, a new approach taking W_u/W _t instead of H/E as the input parameter to determine Vickers indentation fracture toughness is proposed. For this proposed approach, all input parameters can be obtained in one single instrumented indentation test for fracture toughness, thus the test procedure can be simplified significantly. The formula of the newly proposed approach is calibrated by the macroindentation tests on several brittle materials. The validity of the new approach is investigated by comparing its estimation with the old one's.