A two-scale damage model for high-cycle fatigue life predictions following an incremental approach

This study proposes the extension of an incremental damage approach to fatigue life estimate presented by Neves and co-authors, assuming high-cycle fatigue regime, through the adoption of a two-scale damage approach previously proposed by Lemaitre. Under high-cycle fatigue conditions, plastic strain only occurs at the microstructural scale of a material. In this sense, it is not possible to use traditional damage models, whose damage evolution laws are governed by the plasticity and observed in the classical scale adopted by the continuum damage mechanics. An alternative approach was proposed by Lemaitre to separate the material behavior into two scales: one microscopic and the other macroscopic. In addition, a localization law is used to correlate the behavior of the material at both scales. Furthermore, the predictive capacity of the approach proposed in this paper is assessed by comparing the life values predicted by it and those observed experimentally from fatigue tests performed by force control on hourglass-shaped specimens made of grade R4 steel, a material used by the offshore industry in the manufacturing of mooring systems. In conclusion, the approach's predictive capability for fatigue life estimation showed 75% of results within a dispersion band of 2.