Crack growth resistance can be substantially affected by the constraint con
ditions of a structural member which in turn are mainly a function of geome
trical variables and the degree of plasticity. Standardized test methods ar
e restricted to high constraint conditions as represented by deeply cracked
bend-type specimens and may hence lead to conservative structural assessme
nts. It is demonstrated that adjusted testing can be used to reduce the deg
ree of conservatism. Due to rapidly increasing computer capabilities, a com
bination of conventional R-curve testing with micromechanical models emerge
s as an accurate tool which may permit routine evaluations of practical sit
uations in the near future.