Abstract
AbstractWorkpiece rim zone modifications during hard machining can be explained with the high thermo-mechanical loads induced by the cutting process. The formation of White Layers with a fine-grained microstructure by dynamic recrystallization (DRX) is one of those surface modifications that can negatively affect the functionality of a machined part by changing the residual stress state and facilitating crack initiation. As a consequence, the fatigue life of the machined parts is reduced. It is therefore of great interest to understand the thermo-mechanical conditions which induce White Layers formation in order to be able to control them by in-situ measurements if necessary. For this purpose, a cutting force based Soft-Sensor is developed in this study which enables the in-process estimation of White Layer thickness. Therefore, a cutting force based analytical model is used to estimate the resulting temperature fields and correlated with validated numerical chip formation simulations. In addition, the predictions of the White Layer thickness of the analytical model are then compared using light microscopy and the results of the numerical finite element model, in which a DRX model is additionally implemented.
Highlights
Zusammenfassung: Modifikationen der Werkstückrandzone während des Hartdrehens sind auf die hohen thermomechanischen Beanspruchungen zurückzuführen, die lokal auf den Werkstoff einwirken
The formation of White Layers with a fine-grained microstructure by dynamic recrystallization (DRX) is one of those surface modifications that can negatively affect the functionality of a machined part by changing the residual stress state and facilitating crack initiation
A cutting force based Soft-Sensor is developed in this study which enables the in-process estimation of White Layer thickness
Summary
Zusammenfassung: Modifikationen der Werkstückrandzone während des Hartdrehens sind auf die hohen thermomechanischen Beanspruchungen zurückzuführen, die lokal auf den Werkstoff einwirken. High thermo-mechanical loads that are generated during the hard turning process have a great influence on the functionality of a machined part [1, 2] These loads are responsible for microstructural alterations, modification of hardness, residual stress state, mechanical properties, chemical composition and corrosion resistance in the workpiece rim zone [3]. These surface characteristics are collectively known as Surface Integrity [1]. They are typically characterized by a very fine grain size due to dynamic recrystallization (DRX), high hardness and a brittle structure compared to the bulk material [4]
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