This work describes the implementation of a novel high-throughput methodology for the investigation of damage evolution from crack initiation to short crack growth. This methodology is based on the custom-built resonant micro bending fatigue setup. The setup has been enhanced by an in-situ optical acquisition system combined with on-line image processing. With this enhancement the surface evolution of individual grains and their neighbors can be observed in situ. To get statistically significant data, all grains on the surface within the field of view can be tracked in parallel. The micro bending fatigue methodology induces a distribution of stress amplitudes along the sample. The local stress state can be correlated to the position of individual grains. Due to an automated image evaluation, damage evolution in single grains can be recorded, tracked, and evaluated. EBSD analysis before the test allows the determination of the orientation of all grains. And at the same time, the relationship between the optically observable changes on the sample surface and the mechanical stiffness change can be detected by quantitative analysis of the relative frequency change of the sample. This methodology gives in-situ insights of the damage evolution distribution in individual grains and neighbors, depending on the number of cycles, the local stress amplitude, and the grain orientation. This contribution will present the first application of this method to fcc metals.
T. Straub acknowledges the funding by the DFG SPP 1466 for the development of a novel high throughput micro fatigue experiment.