Finite element evaluation of punch-type crack specimens

The single punch shear (SPS) and double punch shear (DPS) specimens have been used in the past for determining Mode II fracture toughness of engineering materials. These two specimens are studied in this paper using a set of linear elastic finite element analysis. The near-crack-tip parameters consisting of stress intensity factors and T-stress are calculated in terms of the crack length ratio a/W for each specimen. It is shown that none of the specimens are subjected to pure Mode II since a considerable value of KI/KII is present for punch-type loading. The T-stress is also negative for both specimens. Using a generalized maximum tangential stress criterion, possible effects from ignoring the contributions of KI and T are investigated for test results obtained from these specimens when the failure is due to brittle fracture.