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Experimental Justification for Proposed Changes to the Measurement of KIc Using ASTM E 399
U.S. Naval Academy, Annapolis, MD
(Received 25 August 1997; accepted 7 April 1998)
During the past five years considerable effort has been devoted to developing a fracture toughness measurement standard that combines the linear elastic stress intensity factor at the onset of crack extension, , and the elastic-plastic fracture toughness measurement quantities, namely, , the J resistance curve (J-R curve), and the corresponding crack tip opening displacement resistance curve (CTOD-R curve). The objective of this effort was to allow the engineer to start with one specimen geometry, conduct a specified test, develop either a or a curve, and then, after application of the relevant size requirements, obtain a valid fracture toughness result. At present, different specimens are required by E 399 and E 1737 (the combination and replacement of E 813 and E 1152), and if the engineer uses the E 399 specimen geometry and test procedure and subsequently finds that the measured fails the E 399 size requirements, new specimens must be machined and tested according to E 1737 to obtain valid fracture toughness measurements.
This paper describes experimental tests that have been conducted in parallel with the development of the new ASTM Standard E 1820-97, a combined fracture toughness test standard that is intended to address this problem. These experimental results show that the standard J integral specimen, incorporating load line crack mouth opening displacement measurements and side grooves, can be used to obtain as presently defined by ASTM E 399. The use of larger ranges is also supported by these results as long as the basic size requirements of E 399 are met and applied to both the specimen crack length and remaining ligament as well as to the specimen gross thickness.
fracture mechanics, linear fracture mechanics, crack initiator, stress intensity factor, size requirements, side grooves, T-stress
Paper ID: JTE12026J
Title Experimental Justification for Proposed Changes to the Measurement of KIc Using ASTM E 399
Symposium , 0000-00-00
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