Ductile Crack Growth Behavior of Structural Steels under Cyclic Loading

Abstract

Fracture mechanics parameter to estimate ductile crack growth properties for structural steels under large scale cyclic loading are discussed using a shallow notched 4-point bend specimen. From the measurement of strain distributions around the extended ductile crack for specimens subjected to various loading histories, it has been shown that the ductile crack initiate and extend under a certain plastic strain level at the crack tip irrespective of loading histories. 90% skeleton CTOD, δ90% skeletonis defined to scale the crack growth under cyclic loading, which will be related to an effective crack tip strain. The crack growth resistance evaluated with δ90% skeleton is found to be independent of loading histories including monotonic, repetitive and cyclic incremental and decremental loading.