Abstract
The titanium alloy Ti-6Al-4V represents a significant metal portion of state-of-the-art aircraft structural and engine components. When critical structural components in the aerospace industry are manufactured with the objective to reach high reliability levels, surface integrity is one of the most relevant parameters used for evaluating the quality of machined surfaces. The residual stresses and the surface alteration induced by machining titanium alloys are critical due to safety and sustainability issues. In this paper, a series of end milling experiments was conducted to comprehensively characterize the surface integrity at various milling conditions. The experimental results have shown that the surface roughness value increases with the feed and the cutting velocity. However, the residual stress state in the surface layer zone is influenced by the variation of the process control variables. Here, compressive residual stresses occur both in cutting and in feed direction. In addition, a new type of sensory tool holder is presented, which should enable the indirect measurement of residual stresses during the milling process.
Zusammenfassung
Die Titanlegierung Ti-6Al-4V wird für die Herstellung von Flugzeugstruktur- und Triebwerkskomponenten verwendet. Wenn kritische Strukturkomponenten in der Luft- und Raumfahrtindustrie mit dem Ziel hergestellt werden, ein hohes Zuverlässigkeitsniveau zu erreichen, ist die Oberflächenintegrität einer der wichtigsten Parameter, die zur Bewertung der Qualität der endbearbeiteten Oberflächen verwendet wird. Die Eigenspannungs- und die Oberflächenveränderung, die durch die Bearbeitung von Titanlegierungen auftreten, sind aufgrund von Sicherheits- und Nachhaltigkeitsaspekten kritisch. In diesem Beitrag wurde eine Reihe von Umfangsfräsversuchen durchgeführt, um die Oberflächenintegrität bei verschiedenen Fräsbedingungen umfassend zu charakterisieren. Die experimentellen Ergebnisse haben gezeigt, dass die Oberflächenrauheitswerte durch Änderungen des Vorschubs pro Zahn und der Schnittgeschwindigkeit nicht signifikant beeinflusst werden. Der Eigenspannungszustand in der Randschichtzone ist jedoch durch die Variation der Prozessstellgrößen beeinflusst. Hierbei treten Druckeigenspannungen sowohl in Schnitt- als auch in Vorschubrichtung auf. Darüber hinaus wird ein neuartiger sensorischer Werkzeughalter vorgestellt, der die indirekte Messung von Eigenspannungen während des Fräsprozesses ermöglichen soll.
Funding source: Deutsche Forschungsgemeinschaft
Award Identifier / Grant number: SPP 2086
Funding statement: The scientific work has been supported by the DFG within the research priority program SPP 2086.
About the authors
Matthias Wimmer studied production and automation at the Munich University of Applied Sciences and the EPF Ecole d’ingénieurs Paris until 2018. Since 2019 he has been a research associate at the Institute for Machine Tools and Industrial Management at the Technical University of Munich. His field of research includes surface engineering in machining.
Muhammed Zubair Shahul Hameed studied metallurgy and materials science at IIT Roorkee and the University of Stuttgart until 2016. Since 2017 he is a research associate at the Chair of Materials Science and Materials Mechanics at the Technical University of Munich. His field of research includes experimental methods for the determination of residual stresses.
Christoph H. Wölfle studied mechanical engineering at the Karlsruhe Institute of Technology and the Technical University of Munich until 2018. Since 2018 he has been a research associate at the Chair of Materials Science and Materials Mechanics at the Technical University of Munich. His field of research includes methods for the simulation of process-induced residual stresses and microstructure changes.
Vanessa Weisbrodt is currently a student of mechanical engineering at the Technical University of Munich. Since 2020 she has been writing her Master’s thesis at the Institute for Machine Tools and Industrial Management, focusing on the durability analysis of titanium components.
Michael F. Zaeh studied Mechanical Engineering at the TUM and received his doctorate in 1993 under Prof. Milberg at the Institute for Machine Tools and Industrial Management (iwb). From 1994 to 1995 he was head of the department for machine tools and manufacturing technology under Prof. Reinhart. In 1996, he moved to a manufacturer of machine tools for gear cutting, where he held various management positions. Since 2002 Prof. Zaeh has been Chairman and Professor of the Chair for Machine Tools and Manufacturing Technology at the iwb of the Technical University of Munich.
Ewald Werner studied materials science, received his doctorate and habilitation at the University of Leoben. He did research at the Erich Schmid Institute for Solid State Physics of the Austrian Academy of Sciences and at the ETH Zurich. From 1997 to 2002 he was Professor of Mechanics at the Technical University of Munich, where he has been head of the Department of Materials Science and Mechanics of Materials since 2002. His fields of work are metal physics and materials mechanics. He is co-author of textbooks and co-editor of several international journals.
Christian Krempaszky studied mechanical engineering, received his doctorate and habilitation at the Technical University of Munich. Since 2016 he has been a private lecturer with teaching authorization for the field of materials mechanics at the Technical University of Munich. Since then he has been working in the field of solid state mechanics with a focus on micro-continuum mechanics at microstructure level, residual stress analysis and mechanical materials testing.
Thomas Semm studied mechanical engineering at the Technical University of Munich until 2015. Since 2020 he has been a member of the Institute’s Management Committee at the Institute for Machine Tools and Industrial Management at the Technical University of Munich. He is head of the Machine Tool Group. His field of research covers the structural dynamics of machine tools.
Acknowledgment
The authors thank the DFG for this funding and intensive technical support.
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