Functionalized subsurface zone for load-oriented fatigue behavior of hardened components

• Applicants: Professor Dr. Bernd Breidenstein; Dr.-Ing. Florian Pape; Professor Dr.-Ing. Gerhard Poll
• Subject Area: Engineering Design, Machine Elements, Product Development
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 468005437

Due to the worldwide economic and ecological development, the application of innovative technologies to protect the environment and conserve resources is necessary. Particularly in manufacturing technology, there is potential for process optimization that is not yet fully understood or fully exploited. For example, residual compressive stresses can be introduced by strengthening the component subsurface zone of cyclically stressed components. Their positive effects on fatigue life have been known for a long time. The residual stress depth can be influenced by an innovative hard turn-rolling process, in which the heat input generated by turning is used for a simultaneous deep rolling process. An application of the hard turn-rolling process to rolling bearings should result in longer bearing fatigue lives. Bench tests showed that a very high maximum and a large penetration depth of the residual compressive stresses alone could not incease bearing fatigue life. The reason for this could be the heat input into the component, which cannot be specifically controlled, and the resulting change in the component edge zone. In previous investigations, no holistic consideration of the component subsurface and its effects on component fatigue life was carried out. For the project applied for here, the working hypothesis is that heat input plays a decisive role in deep-rolling and that a holistic consideration of the component subsurface is necessary. The aim is to investigate the extent to which thermomechanical processing influences the subsurface as a whole and the extent to which individual properties of the subsurface, such as residual stresses, texture, microstructure and its strain hardening state, influence fatigue under cyclic loading and which cause-effect relationships exist. Based on this, optimized edge zone properties are to be defined, specifically adjusted and their positive influence on fatigue life has to be verified. In previous investigations, no holistic consideration of the component subsurface zone and its effects on component service life was carried out. For the project applied for here, the working hypothesis is that heat input plays a decisive role in deep rolling and that a holistic consideration of the component subsurface zone is necessary. The aim is to investigate the extent to which thermomechanical processing influences the subsurface zone as a whole and the extent to which individual properties of the subsurface zone, such as residual stresses, texture, microstructure and its strain hardening state, influence fatigue under cyclic loading and which cause-effect relationships exist. Based on this, optimized edge zone properties are to be defined, specifically adjusted and their positive influence on fatigue life verified.

• DFG Programme: Research Grants