Fatigue Reliability of Casted Wind Turbine Components Due to Defects

Manufacturing of casted components often leads to some (small) defects that are distributed in the volume of the components. These defects are different according to their size, type, orientation and etc. In this paper a probabilistic model is proposed for modeling manufacturing defects and their influence on the fatigue strength of the components. The fatigue life is dependent on the number, type, location and size of the defects in the component and is therefore quite uncertain and needs to be described by stochastic models. In this paper, the Poisson distribution for modeling of defects of component are considered and the surface and sub-surface defects categorized. Furthermore, a model to estimate the probability of failure by fatigue due to the defects is proposed. This model is used to estimate the failure location of component and it is compared to models of defect distributions and locations. Further, an upper bound of reliability is estimated using a modified Miner rule approach for fatigue damage accumulation.