An innovative fatigue life and critical defect size assessment method for structural components with pore defects

Studies on casting components have shown that micro-pore defects reduce the fatigue life. However, current methods are limited for application to full-scale structural components. This study aims to present a general method to assess the influence of type, morphology, and size of the pore defects on the fatigue life of structural components. The ellipsoid and semiellipsoid were introduced to represent the internal and surface pore defects respectively, and the stress concentration factor (SCF) matrix was used to correlate the stress components between pore defect surface and structural surface. To suit to variable amplitude load conditions, the equivalent fatigue stress was introduced to the defect stress gradient (DSG) criterion. The detailed computational flow chart was presented and validated by comparison with the defect surface stress response and published experimental fatigue evidence. Finally, it was used to assess the fatigue life and critical defect size of the casting aluminum gearbox block of high-speed train. This method does not need the finite element model to describe the pore defects directly, and is applicable to the fatigue life and critical defect size assessment of full-scale structural components with pore defects, and can provide a quantitative index between the casting quality and service life of structures.