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.