Professor of Mechanical Engineering, U.S. Naval Academy, Annapolis, MD
Ensign, U.S. Navy, San Diego, CA
(Received 14 January 1991; accepted 30 May 1991)
The development of a “Common Test Method” for fracture mechanics toughness evaluations requires changes in the test specimens used for evaluation of the elastic critical stress intensity factor KIc. The present method. ASTM E 399, does not allow the use of side grooves and load-line crack opening displacement measurements as is common and necessary for J-integral and CTOD elastic-plastic fracture methods like ASTM E 813. E 1152, and E 1290. This paper presents experimental data on two materials that demonstrate that the J-integral type specimen can be used to evaluate KIc in an accurate fashion and that hence a true “Common Method” is possible.
The basic conclusions are that if the secant offset slope is varied to correspond to 2% crack growth, the KQ values measured from specimens with a/W ratios between 0.55 and 0.7 are indistinguishable from standard results. Side grooves do not affect the results as long as an effective specimen thickness is used for the KQ evaluation, and the J-type load-line cutouts appear to have no effect on the measured KQ results.
Paper ID: JTE11890J