Investigation of the effect of residual stresses in the subsurface on process forces for consecutive orthogonal cuts

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

Einfluss der Mikrostruktur härtbarer Fe-Basislegierungen auf den Widerstand gegen Spanabtrag

Die vorliegende Arbeit schafft ein tieferes Verständnis für den Zusammenhang der Mikrostruktur einer härtbaren Fe-Basislegierung und ihrem Widerstand gegen Spanabtrag. Modellwerkstoffe und Modellversuche wurden ausgewählt, um die komplexe spanende Fertigung auf einfachere Systeme im Labormaßstab zu abstrahieren. Dadurch konnte das Verformungsverhalten bei Spanabtrag, sowohl einphasiger (ferritisch, martensitisch) als auch mehrphasiger (+Restaustenit, +Karbidphase) Gefüge, über mehrere Skalen von Dehnraten, Temperaturen und verformten Volumina untersucht werden. Ein energetischer Ansatz wurde genutzt, um die Verformungswiderstände verschiedener Gefüge über die Skalen hinweg zu transponieren. Mithilfe von Eigenspannungsmessungen konnte der Einfluss von konsekutiven Spanabnahmen auf oberflächennahe Eigenspannungsprofile und Prozesskräfte nachgewiesen werden

Genetic influences on schizophrenia and subcortical brain volumes:Large-scale proof of concept

Schizophrenia is a devastating psychiatric illness with high heritability. Brain structure and function differ, on average, between people with schizophrenia and healthy individuals. As common genetic associations are emerging for both schizophrenia and brain imaging phenotypes, we can now use genome-wide data to investigate genetic overlap. Here we integrated results from common variant studies of schizophrenia (33,636 cases, 43,008 controls) and volumes of several (mainly subcortical) brain structures (11,840 subjects). We did not find evidence of genetic overlap between schizophrenia risk and subcortical volume measures either at the level of common variant genetic architecture or for single genetic markers. These results provide a proof of concept (albeit based on a limited set of structural brain measures) and define a roadmap for future studies investigating the genetic covariance between structural or functional brain phenotypes and risk for psychiatric disorders