Predicting fretting-fatigue life under multiaxial and variable loading conditions requires taking into account the effects of stress gradients and the fact that stress concentration areasn where cracks may intiate, are mobile and move, along with the contact front, when the normal load varies. This paper proposes a model, analogous to linear fracture mechanics approaches, to take into account the gradient effects around the contact front through intensity factors and to describe the displacement of the contact front and the non-linear behaviour of the contact partial slip region with an incremental model based on these intensity factors.
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