A Technique for Measuring Load-Line Displacements of Compact Ductile Fracture Toughness Specimens at Elevated Temperatures

A test method developed for measuring load-line displacements in compact ductile fracture toughness (JIc) specimens at elevated temperatures was used to characterize the elastic-plastic (J integral) fracture response of Inconel® X-750 at 75°F (24°C) and ASME SA-387 Grade C steel at 75°F (24°C) and 600°F (316°C). This technique employs a rigid fixture, attached directly to the test specimen, which translates the load-line displacements outside the loading clevises where the displacements are monitored by two linear variable differential transformers (LVDT) inside the elevated temperature environment. To evaluate the proposed displacement measuring technique, displacements and values of J determined by the LVDT method were compared with those determined by the conventional clip gage method. The data obtained from the two displacement measuring techniques were in agreement. In addition, LVDT-determined displacements within the linear-elastic regime were consistent with theoretical displacements.