Fatigue Design of Ferritic-Pearlitic Nodular Cast Iron Components with Surface Discontinuities

Surface and subsurface discontinuities are one of the most important factors affecting the fatigue life of structural cast components. Their location, shape and size vary from component to component, most of them are completely harmless, but one critical defect can lead to in-service failure. Allowable surface discontinuity size finite element (FE) results can be a practical engineering tool for casting design, process planning, and the quality inspection process. Different methods based on the continuum and fracture mechanics applicable on the multiaxial high-cycle fatigue (HCF) and fatigue limit prediction for components with surface discontinuities are compared with experimental results on ISO1083/JS/500-7 nodular cast iron (NCI). Results also confirm, that the fatigue properties of the analysed material in standards truly represent low-end material strength. A design methodology is presented based on the Defect Stress Gradient approach for the display of an allowable surface discontinuity size FE-result for complex components under proportional loading conditions in HCF.