Evaluation of various effects on bend straightening properties of case hardened notched shafts

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The aim of the proposed project is to transfer the knowledge gained within a completed, basic research project to the design of industrial straightening processes. The comparatively small straightening paths that are typical for manufacturing of drive components lead to a localization of plasticity (required for the straightening operation) to areas, in which excessive load stresses and initial residual stresses being characterized by the same sign coincide with low flow limits. In this regard, localized plasticity is often sufficient to achieve the desired straightening effect. Local stress states are significantly affected by notches and shoulders as well as the overall part dimensions, all geometrical features being required for application of the real components. The initial surface layer properties such as the residual stress state, the distribution of retained austenite and the presence of surface damage, respectively, are inevitably a result of the heat treatment. Some findings regarding the straightening behavior of case-hardened and notched components are already available. However, a comprehensive assessment, directly rationalizing effects seen based on individual influencing factors, is not feasible based on current state-of-the-art and, thus, will be elaborated in this project. The first goal is to analyze the impact of individual influence factors on the bend straightening behavior in order to gain an understanding of interrelationships between localized plasticity, transformation of retained austenite and, finally, evolution of local residual stresses. The knowledge gained is then transferred to the project partner to allow for robust design of the bend straightening process.