Surface inspection to detect early fatigue crack initiation in the low cycle fatigue regime of high carbon steel using a scattered light sensor

Fatigue damage is the major factor in the failure of components. During the fatigue loading, the local plastic strain deformation forms persistent slip bands (PSBs) and emerges on the surface as persistent slip markings (PSMs). The PSM can develop roughness and be observed on the surface as extrusions and intrusions, while the intrusions are possible sites of crack initiation. Thus, surface roughness development is a reasonable way to inspect fatigue damage. Many techniques were utilized to inspect and monitor the cracks and fatigue damage progress to protect the components and to predict the remaining lifetime. Most of these techniques consume a lot of measuring time. In this study, a scattered light sensor from Optosurf will be performed to measure and determine the roughness evolution during cyclic loading of a high-strength steel 115CrV3. As a result, the profile and areal measurement from a confocal microscope and the measured Aq values are suitable to illustrate severe surface changes before failure. Moreover, the Aq values using a scattered light sensor are comparable with the results using a confocal microscope (Nanofocus).