A cohesive model for fatigue failure in complex stress-states

A stress-state dependent traction–separation law is combined with an irreversible damage parameter to formulate a cohesive model relevant for life assessment under complex stress-states. Evolution of damage is based on continuum damage laws requiring two cohesive fatigue parameters. For two representative metals, model is able to reproduce typical stress-life response, mean stress effects and sequencing effects under variable amplitude loads. Control of cohesive fatigue parameters on characteristics of the stress-life curve is established, followed by predictions for proportional, cyclic stress-states. With increasing constraint, initiation and growth of damage is more rapid such that higher constraint results in lower life expectancy.