Notch effects on high cycle fatigue life of engine components

Surface notches are favorite positions for fatigue failure of mechanical components because of the stress concentration effects. The presence of a notch on a component under cycling nominal stresses reduces the fatigue strength of the smooth component. In recent years, the finite element method (FEM) has been frequently used to assess the high cycle fatigue (HCF) safety factor in the automotive industry; however, its application requires some consideration. In complex geometries under dynamic loading, the FE stress results give no indication of the type of the loading. In this study, two different methods based on the relative stress gradient and the critical distance approaches are considered in order to evaluate the effect of notch geometries on HCF safety factors of notched specimens. In the first approach, the notch effect has been considered by introducing the relative stress gradient parameter. The critical distance method has also been very successful in predicting the fatigue limits of notched specimens using the elastic FE analysis and can be employed for determining the HCF safety factors of complex engine components. Results of both methods have been compared with the experimental data.

Keywords:

Notch , High cycle fatigue , Engine components , Relative stress gradient method , Critical distance method