Fracture Mechanics Investigations at 7 K of Structural Materials with EDM Notched Round and Double Edged - Bars

Fracture mechanics investigations are performed at 7 K with small round bar specimens having an electro discharge machined (EDM) notch around the girth. Various aged and unaged structural materials are tested at 7 K to develop a measurement procedure for critical elastic — plastic toughness estimates based on J-integral method. The load — versus — displacement curves determined using symmetrically arranged high resolution extensometers are evaluated using new software to compute directly the J-values. The results for the investigated structural materials confirm the excellent performance of this novel test method. The effects of stroke rate, net section diameter, and fatigue precracking are investigated at 7 K within this context to determine the critical factors affecting J — values. The method is applied to small double edged — notched specimens to further support the development.