Determination of Fracture Toughness J Ic Under Quasi-Static and Dynamic Loading Conditions Using Wedge Loaded Specimens

Abstract A study of the variation of fracture toughness of American Iron and Steel Institute (AISI) 1045 (Unified Numbering System [UNS] G10450) steel in the annealed condition, which exhibits elastic-plastic behavior at the crack tip, with loading rates ranging from quasi-static to dynamic conditions was undertaken. A wedge loaded compact tension (WLCT) specimen geometry was used in both testing conditions. The onset of crack propagation was detected using a strain gage mounted near the crack tip. The fracture parameter JIc decreases by about 50% when the loading rate ˙KI increases from 0.5 to about 106 MPa · m½ s−1. The measured values of JIc using WLCT specimens were confirmed from previous data on this material using standardized three-point bending specimens as well as from evaluation of JIc from stretch zone width measurements using scanning electron microscopy of the fracture surface of the WLCT specimens.