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A new combined fatigue model that considers a defect based and a stress based mechanism is presented. The defect part is based on the weakest link theory, where the integration is performed either over the surface area or the volume of the component. The stress based mechanism is described by the normal distribution, where the stress is either the largest occurring stress value, the point stress, or the point stress adjusted with the stress gradient, denoted the gradient adjusted point stress. Experiments on notched specimens have been performed. The combined model behaves almost like only a stress based model at high failure probabilities. At low failure probabilities, results are less clear. There, the stress based model is not accurate and the defect based model (both for area and volume) dominates. Using the gradient adjusted point stress in the stress based model and the volumetric weakest link integral in the defect based model being described by gives the best overall fit to the probability of failure. It is noted that for design with respect to high failure probabilities (> 20 %), it is enough use only the gradient adjusted stress based model.

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