Cycle Number Estimation Method on Fatigue Crack Initiation using Voronoi Tessellation and the Tanaka Mura Model

This paper deals with the short crack initiation of the material 9Cr-1Mo (P91) under cyclic loading at different temperatures (T = 24 °C and T = 650 °C) concluded with the estimation of the short crack initiation Wöhler (S/N) Curve. Short crack initiation under the influence of microstructures is analyzed to derive their crack initiation curves. An artificial but representative microstructural model microstructure was generated using the Voronoi tessellation (VT) method and the non-uniform stress distribution is calculated by Finite Element Method accordingly afterwards. The number of cycles needed for crack initiation is estimated on the basis of the stress distribution in the microstructural model by applying the physically-based Tanaka-Mura model (TMM). Since mechanical properties are highly correlated with temperature, the research indicates that the number of cycles required to initiate cracks at room temperature is significantly higher than at elevated temperatures.