USE OF THE INTERCEPT METHOD FOR J-R CURVE CONSTRUCTION OF C(T) SPECIMENS WITHOUT CRACK EXTENSION DATA

摘要

The construction of a J-R curve requires consideration of the stable crack extension process,and the appropriate correction for the incremental crack growth. Following Standard ASTM E1820, the J resistance curve is obtained from a single specimen test, in which the actual crack length is measured concurrently with the fracture test, by the unloading compliance method, or other similar techniques. Recently, Donoso, Vasquez and Landes (DVL) developed a method for obtaining the crack size in a test in which there is stable crack extension, but has only the P-v data, and the initial and final crack sizes, a_0 and a_f, respectively, as inputs. The DVL method was introduced as an alternative to the unloading compliance and normalization procedures included in E1820, and presents notable advantages when the full a-v data are not available. Inherent to this novel crack size evaluation methodology, is the notion of the "crack growth law" postulated earlier by Donoso, Zahr and Landes. The method presented here, designated as the "intercept method', is used with C(T) specimen data that have crack extension measured by the unloading compliance method. The results are quite encouraging, and the method is extended to one example in which a full a-v record is lacking, and there are only initial and final crack sizes available.