Frequency-Dependent Cohesive-Zone Model for Fatigue

This paper is concerned with the development and application of a frequency-dependent cohesive-zone model (CZM) for crack-growth analysis of low and high-cycle fatigue. The new model makes use of recent advances by combining a modified version of a recently developed frequency-dependent trapezoidal cohesive-zone model (Salih et al., 2017) and a new loading-unloading hysteresis damage model with fast-track facility. The new combined model offers an alternative approach to capture frequency effects and at the same time deliver accuracy comparable to the loading-unloading hysteresis damage model along with the computational efficiency of the equally well-established envelope load-damage model. The model provides for the first time a methodology that accommodates frequency dependency yet delivers high computational efficiency.

In order to demonstrate the practical worth of the approach, the frequency effect observed with fatigue crack growth in austenitic stainless-steel 304 is analysed. It is found that the crack growth decreases with increasing frequency up to a frequency of 5 Hz after which it levels off. The behaviour, which can be linked to martensitic phase transformation, is shown to be accurately captured by the new mode