Since geometry is the element with major influence on the fatigue strength of 3D metallic components, a method to optimize their shape with respect to fatigue under proportional loading is presented. The local stress life concept according to the FKM-guideline is used to construct a non-standard safety factor response function, which includes the mean stress effect and the stress distribution support effect in the local fatigue strength. At each node of the surface, the local safety factor is obtained from a Kreisselmeier-Steinhauser aggregation of the safety factors in the three principal directions to smoothly take the lowest one. A general workflow to optimize such components with the aforementioned safety factor function is implemented using Abaqus and VisPER for pre- and post-processing, PERMAS for the shape optimization, and Python codes for the interfaces. Such workflow is successfully applied to the optimization of a cantilever beam, a fuel rail and a part of a gear housing obtaining strength improvements of 37%, 53%, and 90% respectively. In parallel, the influence of the mean stress and the support effect are analyzed by comparing the optimizations with the following safety factor response functions: taking into account both effects, leaving out the support effect, and leaving out both the support and the mean stress effects which is a scaled stress-funtion. With the three functions, a significant component strength improvement is obtained, being the best with the formulation where the complete safety factor function is employed, followed closely by the one that does not include the support effect, and then by the remaining one. No much difference is found between the first and the second formulation. Besides, for very local geometry modifications (e.g. Fuel Rail and Gear housing), it is found that the mean stress effect has minimal or no influence. This contrasts with the cases in which the load is not fully alternating and tensile and compressive regions appear (e.g. Cantilever beam), where further improvement can be obtained by including the mean stress effect.     «

Since geometry is the element with major influence on the fatigue strength of 3D metallic components, a method to optimize their shape with respect to fatigue under proportional loading is presented. The local stress life concept according to the FKM-guideline is used to construct a non-standard safety factor response function, which includes the mean stress effect and the stress distribution support effect in the local fatigue strength. At each node of the surface, the local safety factor is ob...     »