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Refraction computed tomography

Application to metal matrix composites

3D Refraktions-CT-Anwendung für Metall-Matrix-Composite (MMC)
  • Bernd R. Müller , Axel Lange , Michael Harwardt , Manfred P. Hentschel , Bernhard Illerhaus , Jürgen Goebbels , Joachim Bamberg and Falko Heutling
From the journal Materials Testing

Abstract

For the first time metal matrix composites have been investigated by 3D computed tomography combined with enhanced interface contrast due to X-ray refraction. The related techniques of refraction topography and refraction computed tomography have been developed and applied during the last decade to meet the actual demand for improved non-destructive characterization of high performance composites, ceramics and other low-density materials and components. X-ray refraction is an optical effect that can be observed at small scattering angles of a few minutes of arc as the refractive index n of X-rays is nearly unity (n = 1 − 10−6). Due to the short X-ray wavelength, the technique determines the amount of inner surfaces and interfaces of nanometer dimensions. The technique can solve many problems in understanding micro and sub microstructures in materials science. Applying 3D refraction computed tomography, some questions could be clarified for a better understanding of fatigue failure mechanisms under cyclic loading conditions.

Kurzfassung

Erstmals wurden MMCs mit Hilfe der Interface-Kontrast verstärkenden Röntgen-Refraktions-Technik in Kombination mit der 3D-CT-Technik untersucht. Die Methode der Röntgen-Refraktions-Topography sowie der Röntgen-Refraktions-Tomography wurden in den letzten Jahren speziell für die zerstörungsfreie Charakterisierung von Leichtbau-Hochleistungs-Werkstoffen wie Verbund-Werkstoffen und Keramiken entwickelt. Die Technik basiert auf der Refraktion von Röntgenlicht an Grenzflächen zwischen Bereichen unterschiedlicher Elektronendichte wie z.B. Faser- und Matrix-Werkstoff. Auf Grund der kurzen Röntgen-Wellenlänge hat der Brechungsindex einen Wert dicht bei eins, sodass der Streuwinkel nur wenige Bogenminuten beträgt. Der Vorteil der kurzen Wellenlänge besteht jedoch darin, dass Poren und Risse detektiert werden können, deren Größe im Nanometerbereich liegen. Damit kann die Refraktions-Technik zum besseren Verständnis von Mikro- und Submikro-Strukturen in der Materialwissenschaft eingesetzt werden. Mit der hier vorgestellten Refraktions-CT wurden Ermüdungsmechanismen an MMCs, bestehend aus SiC-Faser verstärktem Titan (Ti6242) untersucht. Die Messungen wurden am Röntgen-Messplatz der BAM (BAMline) am Synchrotron-Speicherring-BESSY in Berlin Adlershof durchgeführt.


Dr. rer. nat. Bernd R. Müller, born in 1957, studied physics at the Technical University of Berlin where he did his doctorate 1990 in atomic physics. He then continued basic research at various European Synchrotron Radiation Laboratories. Since 1995, he has managed a hard X-ray research project on new X-ray topography techniques at the BAM test station at Berlin Synchrotron Radiation Laboratory BESSY.

Dipl.-Phys. Axel Lange, born in 1948, studied physics at the Technical University Berlin, where he received his M.Sc. After basic research in the X-ray analysis of amorphous materials, he became the collaborator with BAM in 1987, developing computer controlled techniques for X-ray topography.

Michael Harwardt, born in 1955, studied electronics engineering at the Technical College Berlin. In 1991, he joined BAM, where he is the engineer responsible for the construction of X-ray topography systems, computer controlled devices and electronics at the topography laboratory.

Prof. Dr. rer. nat. Manfred P. Hentschel, born in 1943, studied physics at Freie Universität Berlin, where he received his PhD. in 1981. After postdoctoral activities in X-ray and the neutron scattering of bio membranes and polymers, he joined BAM in 1987, where he is head of the laboratory VIII.32 “Generalised X-Ray Topography”.

Dr. rer. nat. Bernhard Illerhaus, born in 1956, studied physics at the Freie Universität Berlin, where he received his PhD in 1987. He joined the group of computed tomography at BAM in 1987, since than working on micro-CT, Linac driven CT and image processing.

Dr. rer. nat. Jürgen Goebbels, born in 1946, has studied physics at the Technical University of Karlsruhe where he received his PhD in 1981 on amorphous super-conductors. After some years of basic research about Nuclear Magnetic Resonance on superconductors at the Freie Universität Berlin he joined to BAM in 1982. Since 1986 he is the head of the working group Computed Tomography.

Dr. rer. nat. Joachim Bamberg, born in 1957, studied physics at the University of Saarbrücken, where he received his PhD in 1988. He joined MTU Aero Engines GmbH Munich, where he tested and characterised new materials and constructions. Since 2001 he conducts the department of non-destructive testing at MTU.

Dr.-Ing. Falko Heutling, born in Schwerin, Germany in 1970, studied metallurgy and materials science at the “Technical University Bergakademie Freiberg”. He received his doctorate in 1999 at the University of Kaiserslautern (“Fracture mechanisms in carbon fibre reinforced plastics”). After his dissertation he was a member of the DaimlerChrysler Exchange Group (Austauschgruppe), Research and Technology. He coordinated the research activities of MTU Munich Aero Engines and DaimlerChrysler, Research and Technology, in the field of metal-matrix composites. Since 2001 he has been responsible for the development of new materials applications at the MTU Aero Engines GmbH Munich.


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Published Online: 2013-05-26
Published in Print: 2004-06-01

© 2004, Carl Hanser Verlag, München

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