Daniel Bellett

A flexible HCF modeling framework leading to a probabilistic multiaxial Kitagawa-Takahashi diagram

This article describes a flexible modeling framework which leads to the construction of a probabilistic, multiaxial Kitagawa-Takahashi diagram. This framework has been developed following experimental observations that clearly indicate that two independent fatigue damage mechanisms can be activated, at the same time, in metallic materials. Specifically, one damage mechanism is associated with crack initiation and the other with crack arrest. It is postulated that these damage mechanisms are more appropriately modeled using two different fatigue criteria or, more specifically, two completely different approaches to fatigue (i.e. a classical multiaxial fatigue criterion and a LEFM type criterion). Hence, the proposed modeling framework provides the possibility of combining any two suitable criteria, in a probabilistic framework based on the weakest link hypothesis and results in the continuous description of the Kitagawa diagram for any multiaxial stress state. It is shown that under certain conditions this approach is equivalent to the classical El Haddad approach to the short crack problem encountered in LEFM. However, the proposed framework is easily extended to multiaxial loading conditions. This modeling framework is demonstrated in detail via its application to multiaxial fatigue data for data taken from the literature.