The reliable detection and precise assessment of white etching layers (WEL) are key challenges in the investigation of a component’s surface integrity. This paper proposes an innovative methodology for evaluating the extent of WEL in quenched and tempered steels, machined by Boring and Trepanning Association (BTA) deep hole drilling. Micrographs obtained by light microscopy were partitioned into classes by three methods, separating the WEL from the base material and the embedding resin. Traditional manual segmentation was performed as a benchmark for automatic segmentation methods. A gray level thresholding-based method served for the segmentation of micrographs partitioned into subsets. In addition to conventional manual and thresholding-based segmentation, a machine learning-based approach for image segmentation was applied. The segmented images were further analyzed by a newly developed set of algorithms, implemented to obtain detailed information on the WEL, e.g. their average thickness as well as the area covered by WEL in the micrographs. Results indicate that both, gray level thresholding, as well as machine learning-based image segmentation, show potential for the automated diagnosis and assessment of WEL. They both yield quantitatively similar, but less biased results compared to manual segmentation.
Ultrasonic-assisted machining processes with diamond tools are regarded as a key technology for reducing the catastrophic tool wear occurring while machining steel workpieces with surface roughness in optical quality. Economical machining of various steel materials with significantly reduced wear of the diamond tool further improved since elliptical vibration cutting with a superimposed ultrasonic tool motion was introduced. How far the result of the machining process is influenced by the changing process kinematics of the ultrasonic motion alone or by the energy introduced into the material by the energy of an ambient ultrasonic field has not been investigated yet. The presented work is dedicated to superimposing an ultrasonic field into the workpiece during machining using an ultrasonic bath. Machining experiments with cutting grooves and particular surfaces with monocrystalline diamond tools are carried out on brass, copper and aluminum. The process forces show a decrease with the increase of the ultrasonic energy of up to 50 percent, while the surface roughness remains uninfluenced by the ultrasonic energy. The results indicate that the ultrasonic induced softening has an influence on the cutting process, which could improve the machining of brittle hard materials in future investigations.