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Consequences of Micro-Milled and Laser Structured Surfaces of CP-Titanium on Tension-Compression Fatigue Behaviour

Component surfaces can be modified by micro-structuring processes like micro-milling or laser structuring for functionality reasons. This modification induces small notches, whose dimensions are in the same order as the grain size. This could have an influence on the mechanical properties. This paper presents the results of tension-compression fatigue tests with structured and – for comparison – with unstructured micro-tensile specimens of cp-titanium grade 2. Longitudinal metallographic microsections illustrate the grain size of the microstructure and the geometry of the notches. The results of the fatigue tests show the influence of the notches on lifetime and endurance limit. With a Scanning Electron Microscope (SEM) the fracture surfaces, the crack initiation sites, and the crack propagation areas of all samples were analyzed. With these analyses we want to determine which notch structure dimensions relative to the grain size are tolerable.