These slides were presented at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

The fatigue strength of spring-hard components is significantly influenced by the manufacturing process. According to the FKM guideline for springs, it is possible to evaluate the fatigue strength of such components, whereby manufacturing process parameters such as shot peening, heat treatment and the residual stresses induced by the manufacturing process play a crucial role. Residual stresses that are induced during the manufacturing process have a direct effect on the stress distribution and thus on the fatigue life of the components. However, the exact determination of these residual stresses is associated with considerable challenges, as detailed and time consuming production simulations are usually required for this. In order to reduce this effort, an innovative approach was developed that efficiently and precisely determines the process-induced residual stresses. This method is based on performing a large number of non-linear calculations in order to generate a broad database of residual stresses in round wires after the coiling process. Based on this data, a convolutional neural network was trained that can precisely predict the stress profiles in the wire cross-section after coiling. The input parameters used in the computations include the spring geometry and the material class of the spring-hard materials. The output of this surrogate model is the stress state in the wire cross- section and thus provides a reliable basis for taking the residual stresses into account in the fatigue prediction. A significant benefit of this method is the possibility of combining this process step with other manufacturing processes, such as shot peening and heat treatment, and also taking their influence on the residual stress distribution into account. This creates a complete view of the process-induced residual stresses along the entire production chain. The method presented allows a more efficient and comprehensive consideration of residual stresses when determining the fatigue strength of spring-hard components. This not only improves the accuracy of fatigue strength evaluations, but also enables the manufacturing processes to be optimized with regard to the fatigue strength and durability of the components. This approach therefore represents a significant advance in the field of fatigue strength analysis and optimization.