R-curve testing and its relevance to structural assessment

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.