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The quality and surface integrity of machined parts is influenced by residual stresses in the subsurface resulting from cutting operations. These stress characteristics can not only affect functional properties such as fatigue life, but also the process forces during machining. Especially for orthogonal cutting as an appropriate experimental analogy setup for machining operations like milling, different undeformed chip thicknesses cause specific residual stress formations in the subsurface area. In this work, the process-related depth profile of the residual stress in AISI 4140 was investigated and correlated to the resulting cutting forces. Furthermore, an analysis of the microstructure of the cut material was performed, using additional characterization techniques such as electron backscatter diffraction and nanoindentation to account for subsurface alterations. On this basis, the influence of process-related stress profiles on the process forces for consecutive orthogonal cutting strategies is evaluated and compared to the results of a numerical model. The insights obtained provide a basis for future investigations on, e. g., empirical modeling of process forces including the influence of process-specific characteristics such as residual stress., Production engineering;Vol. 15. 2021, pp 873���883

Das Thema dieser Dissertation ist die Untersuchung der Bildung von laserinduzierten periodischen Oberflächenstrukturen (engl. laser-induced periodic surface structures) \(\bf {sogenannten}\) LIPSS oder auch Ripples genannt. Die Motivation war es, den physikalischen Hintergrund von LIPSS zu erforschen und Informationen zu sammeln, was in der Literatur noch nicht eindeutig geklärt ist. Der Fokus lag auf der Kontrolle der Periode und Orientierung der LIPSS durch Veränderung der Laserwellenlänge und der Umgebungsbedingungen. Es wurde festgestellt, dass die Welligkeit in flüssiger Umgebung viel kleiner ist und eine andere Orientierung hat. Das zeigt, dass die Umgebung und die Hydrodynamik eine wichtige Rolle auf die Eigenschaften der LIPSS haben. Im letzten Kapitel wird der Farbeffekt durch LIPSS untersucht. Die Ergebnisse dieser Studie zeigten wertvolle Erkenntnisse, wie sich die optischen Eigenschaften der Oberfläche verändern und so die spektralen Eigenschaften für Farben gesteuert werden können. The main topic of this dissertation is the study of the formation of laser-induced periodic surface structures (LIPSS), or ripples. The motivation was to reveal valuable information regarding to the physical background of ripples, which is still not clear in literature. For this, I focused on the control of the LIPSS period and orientation by altering the laser wavelength and the environmental conditions. It was found that ripples have much smaller period in liquid environment and totally different orientation, showing that the environment and the hydrodynamics can play a crucial role on the ripples characteristics. In the last chapter colourizing effect caused by ripples is studied. The findings of this study reveal valuable information of how the optical properties of the surface change and the way to control the spectral characteristics of the colours.