Load path-dependent fatigue capability of forward rod extruded case hardening steel 16MnCrS5

With the increasing importance of climate change and the scarcity of resources, the requirements for energy efficiency, emission reduction and resource conservation are increasing. In this context, forming technologies offer considerable potential for light-weight construction, cost and resource efficiency. Forming-induced ductile damage in the form of voids and their growth is currently neglected in the design of components. Commercially, component design is based primarily on the mechanical material properties and the use of safety factors. Incorporating knowledge of forming-induced ductile damage, especially voids, into the design process allows for improved designs and better utilization of lightweight construction. This study focuses on the assessment of the influence of load paths on the fatigue performance and damage mechanisms. Specifically, under axial-torsional fatigue loading, the materials fatigue performance is influenced by the phase shift, which represents the phase angle between cyclic axial and torsional loading. Among the load paths investigated, axial loading significantly contributes to the damage evolution. A phase shift of 90° between axial and torsional loading resulted in a 37% increase in the initial load level. For a total strain amplitude of 0.0025 and an angular amplitude of 10°, the number of load cycles decreased by about 20% compared to a phase shift of 90°. Therefore, studying the influence of damage-sensitive load paths is critical to assess both damage evolution and the fatigue loading capability of formed components.