Numerical Modeling of the Redistribution of Residual Stresses in Deep Rolled Cross Bores in Shafts from GJS700-2

Lightweight design efforts are generally limited by highly stressed areas. In the case of shafts with cross bore the cross bore forms a notch. Due to geometry and position, those notches lead under cyclic torsional loading to stress peaks in the component, which appear as highly stressed areas. In order to counteract tensile stress peaks, compressive residual stresses may be induced into the surface layer by means of surface treatments such as deep rolling. The induction of compressive residual stresses may delay crack initiation and growth. When deep rolled components are subsequently subjected to cyclic loading, the induced residual stresses are redistributed until a stable residual stress state is established, which is decisive in the assessment of the fatigue strength. The influence of deep rolling on the surface properties of cross bores in shafts made of GJS700 and the redistribution behavior of the induced residual stresses under subsequent cyclic torsional loading is mostly unknown. The objective of this work was therefore to identify the cause-effect relationships between the deep rolling parameters (pressure, overlap) as well as the cyclic loading and the resulting surface properties. Therefore, experimental investigations of deep rolling and of the subsequent cyclic torsional loading were carried out. Subsequently, the process sequence was modeled numerically consisting of a deep rolling and a torsion model. The experimental tests were used to validate the models. Finally, the cause-effect relationships between the deep rolling parameters on the residual stresses and the redistribution due to cyclic torsional loading were investigated.