Modeling and analysis of high -speed machining of aerospace alloys
Abstract
The objective of this study is to develop scientific tools for predicting microscopic and macroscopic quantities in machining and thereby analyze the high speed face milling of aerospace alloys using popular cutting tool materials. The aerospace alloys studied in this research are 7075-T6 aluminum and Ti-6Al-4V titanium. This work presents the mechanistic modeling of the dynamic cutting force for longitudinal turning, boring and face turning processes. Particular attention is paid to the inclusion of cross coupling between radial and axial vibrations in the force model. The inclusion of cross coupling facilitates prediction of the unstable-stable chatter phenomenon which usually occurs in certain cases of finish longitudinal turning due to process nonlinearity. Experimental tests are performed on AISI 4140 steel and Waspaloy workpieces to justify the chatter predictions of the dynamic force model in longitudinal turning and face turning respectively. An extended oblique machining theory applicable to the analysis of 3-D machining is also presented. Existing theories are evaluated to identify suitable formulations which are used with necessary modifications for predicting various microscopic quantities pertaining to three dimensional machining. Actual chip flow angles extracted from measured forces, to account for the nose radius effect, are used to predict important quantities such as shear plane angle, effective rake angle and shear flow angle instead of available models. Validation experiments are conducted in the realms of conventional and high speed machining and various process conditions of cutting mechanics are calculated. This research is also concerned with an investigation on high-speed face milling of 7075-T6 aluminum and Ti-6Al-4V titanium with a single insert cutter. The results are analyzed in terms of cutting forces, chip morphology, and surface integrity of the workpiece machined with popular tool materials. The extended oblique machining theory developed in this research is used in understanding the mechanics underlying the high speed machining of 7075-T6 aluminum. In contrast, finite element simulations are employed for understanding the deformation of Ti-6Al-4V titanium. It is shown that shear localization can occur at higher feeds even for 7075-T6 which is known to produce continuous chips and feed has a positive impact on compressive residual stresses.
Degree
Ph.D.
Advisors
Shin, Purdue University.
Subject Area
Mechanical engineering
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