Crack tip opening displacement estimation formulae for C(T) specimens

Improved formulae for estimating crack tip opening displacement (CTOD) from test records of compact tension (C(T)) specimens are developed. Two-dimens ional, plane strain, finite element analyses of 1T C(T) specimens are made for normalized crack depths, a/W, of 0.40-0.70 using Ramberg-Osgood materia l behavior with strain hardening coefficients n = 5, 10, and 20. Finite ele ment predictions of J, CTOD, crack mouth opening displacement (CMOD) and lo ad are used to obtain proportionality constants relating the area under the load-CMODpl curve to J(pl), and J to CTOD in terms of a/W and n. Improveme nts in CTOD estimates of 25% over existing estimation methods are obtained. Correction factors for displacements measured on the specimen front face i nstead of the load line are also examined. (C) 2000 Elsevier Science Ltd. A ll rights reserved.