Influence of near-surface microstructural elements and their geometrical properties on the fatigue strength

• Applicants: Professor Dr.-Ing. Thomas Lampke; Dr.-Ing. Lisa Winter
• Subject Area: Metal-Cutting and Abrasive Manufacturing Engineering
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 547640565

Many components have to endure periodically occurring load changes during their life cycle. Of great technical and economic interest are long service lives with high tolerable loads. For such cyclically loaded components, the selection of materials and the adaptation of the geometric design with regard to a high achievable fatigue strength is necessary. Related to the application, a minimum number of load cycles must be endured without cracks. As the component surface is the preferred location for crack initiation under high cycle fatigue loading, the geometric and material properties have a decisive influence on the fatigue strength. This means that in addition to strength, hardness and the macroscopic surface topography, the notch effects resulting from the microstructural elements also have an influence on the microscale. However, these microstructure-based influencing factors have so far been insufficiently researched in terms of their effect on fatigue strength. A fundamental and systematic investigation of their influence on fatigue strength is therefore urgently required. The research hypothesis of the project is that, in addition to the chemical composition of the microstructural constituents, their shape, size, orientation or distribution and thus the geometric shape of the microstructural elements also significantly influence the fatigue strength of a component. This means that all microstructural elements identified as relevant must be taken into account when designing a component for improved application properties. The aim of the project is by defined designing of the near-surface microstructures to understand their interactions with the microscale notch effects and local residual stress states occurring there as well as the cracking behaviour of test specimens under cyclic loading. Using the example of rotary bending load, the influence of the near-surface microstructure on the fatigue strength is to be determined not only qualitatively but also quantitatively.

• DFG Programme: Research Grants
• Major Instrumentation: 4-Punkt Umlaufbiegeprüfsystem