A mechanistic approach to the Kitagawa–Takahashi diagram using a multiaxial probabilistic framework

• A probabilistic modelling framework is proposed to model multiple damage mechanisms.
• The framework combines any two fatigue criteria that can model the two damage mechanisms.
• Leads to probabilistic multiaxial Kitagawa–Takahashi Diagrams.
• Good correlation with experimentally data form literature is observed.

The aim of this paper is to propose a flexible multiaxial modelling framework that is capable of combining two fatigue damage mechanisms so as to continuously describe the Kitagawa–Takahashi diagram. It is proposed that this diagram represents two distinct fatigue damage mechanisms: one associated with crack initiation (or microstructurally small cracks) and the other with crack propagation (or long cracks). It is further postulated that these damage mechanisms are more appropriately modelled using different fatigue criteria. A probabilistic modelling framework is proposed in which any two suitable fatigue criteria can be combined in order to simultaneously model both damage mechanisms and the transition between them. This framework is based on the weakest link hypothesis and results in a probabilistic Kitagawa–Takahashi type diagram.