J-R Curve Determination Using Precracked Charpy Specimens and the Load-Drop Method for Crack Growth Measurements

摘要

J-R curves for two aluminum alloys, a titanium alloy and a high strength-low alloy steel at two different strength levels were determined using precracked Charpy specimens. Three methods were used to measure crack growth: (1) multi-specimen, (2) compliance unloading, and (3) the load-drop method. The load-drop method assumes that crack growth occurs only after peak load has been attained and the amount which the load decreases after peak load is related to the size of the uncracked ligament. Comparisons between the three methods for all of the materials show remarkably similar J-R curves. Also, using these curves to determine a JIc indicates very little difference between the load-drop method and the others in the measurement of toughness.