ComInt – Improved fatigue life by microstructure-based control of component integrity taking into account forming history

 

The accurate modelling of fatigue mechanisms is a key factor for the safe design of components under cyclic loading conditions. However, the fatigue resistance of a material is altered in the course of most manufacturing processes and difficult to predict. Forming technologies have significant advantages in comparison with cutting technologies. Those advantages are to be found in efficient material usage, energy and resource efficiency as well as improved material properties. The improvement of material properties of formed components arises from the strain hardening induced in the course of cold and warm forming and resulting favourable fiber flow of complex shape formed components. The applicability of the forming technology for components operating under fatigue conditions is still limited. This is explained by the lack of knowledge about the effect of manufacturing-induced property modifications on the final service behaviour. In particular the influence on cyclical load cases cannot be fully explained so far. The complexity of the manufacturing processes leads to challenges in the fine-tuning of the underlying process parameters of the manufacturing processes to optimise the final component’s in-service behavior. This holds true especially when such adjustment is based on experimentally determined properties of the fatigue resistance.

The aim of the research project is to evaluate fatigue strength in order to characterise component integrity. The industrially applied manufacturing chain of solid forward extrusion and heat treatment as well as the research manufacturing chain including solid forward extrusion and subsequent mechanical surface treatment will be studied. The research project will provide the knowledge about the influence of micromechanical features on the component integrity and explain the cause-and-effect relationships of the forming history and component integrity. With this, the material changes during component operation and the interaction of the process parameters, such as deep rolling pressure and shoulder opening angle, and the fatigue strength can be traced. In order to prove the ability of the newly developed concept to improve the manufacturing processes, the component performance after the selected manufacturing processes will be studied.