Gerd Weidemann
Bundesanstalt für Materialforschung und -prüfung
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Publication
Featured researches published by Gerd Weidemann.
Proceedings of SPIE | 2008
Alexander Rack; Heinrich Riesemeier; Simon Zabler; Timm Weitkamp; Bernd R. Müller; Gerd Weidemann; Peter Modregger; John Banhart; Lukas Helfen; Hans Georg Gräber; Richard Heldele; Boaz Mayzel; Jürgen Goebbels; Tilo Baumbach
The BAMline at the BESSY light source in Berlin and the TopoTomo beamline at the ANKA synchrotron facility in Karlsruhe (both Germany) operate in the hard X-ray regime (above 6 keV) with similiar photon flux density. For typical imaging applications, a double multilayer monochromator or a filtered white beam is used. In order to optimise the field of view and the resolution of the available indirect pixel detectors, different optical systems have been installed, adapted, respectively, to a large field of view (macroscope) and to high spatial resolution (microscope). They can be combined with different camera systems, ranging from 16-bit dynamic range slow-scan CCDs to fast CMOS cameras. The spatial resolution can be brought substantially beyond the micrometer limit by using a Bragg magnifier. The moderate flux of both beamlines compared to other 3rd generation light sources is compensated by a dedicated scintillator concept. For selected applications, X-ray beam collimation has proven to be a reliable approach to increase the available photon flux density. Absorption contrast, phase contrast, holotomography and refraction-enhanced imaging are used depending on the application. Additionally, at the TopoTomo beamline digital white beam synchrotron topography is performed, using the digital X-ray pixel detectors installed.
Tm-technisches Messen | 2007
Michael Neugebauer; Uwe Hilpert; Markus Bartscher; Norbert Gerwien; Stefan Kunz; Frank Neumann; Jürgen Goebbels; Gerd Weidemann
Es wird ein neu entwickeltes geometrisches Normal zur Prüfung von Röntgen-Mikro-Computertomografiemesssystemen (μCT-Messsystemen) sowie ein Verfahren zur Herstellung und Kalibrierung beschrieben. Das Normal ermöglicht die Prüfung von μCT-Messsystemen mit den Verfahren der klassischen Koordinatenmesstechnik nach ISO 10360 bzw. VDI/VDE 2617 sowie dem Verfahren des Soll-Ist-Vergleiches von Referenz- und μCT-Messdaten. A novel geometrical standard for testing X-ray-micro-computertomography measuring systems (μCT) and methods for manufacturing and calibration are described. This standard enables the testing of μCT measuring systems to use test procedures of classical coordinate measurement technique according to ISO 10360 resp. VDI/VDE 2617 as well as the nominal-actual comparison of μCT data against reference data.
Micron | 2009
Carsten Kamenz; Gerd Weidemann
Remarkable results obtained while searching for suitable contrasting agents for tomographical imaging are presented. Book lungs, the respiratory organs of scorpions (Scorpiones, Arachnida), served as challenging objects in terms of fragility and preparatory requirements, as well in terms of size differences between the entire organ and its functional subunits (the lamellae). The problem of tissue contrast was investigated using various metals, but most successfully addressed using osmium. Gaseous osmium tetroxide exposure with subsequent ethanol treatment yielded the best results. A constant and thorough staining of the book lungs was achieved, easing book-lung visualization using 3D-reconstructions from microCT scans.
Materials Testing-Materials and Components Technology and Application | 2008
Gerd Weidemann; Ronny Stadie; Jürgen Goebbels; Bernd Hillemeier
Abstract A preferential orientation of fibres is induced by the production process of fibre reinforced autoclaved aerated concrete. For a better understanding of the development of the fibre arrangement during the foaming process of the concrete, digital radiography was used to study the evolution of orientation in situ. The strength and the deformation behaviour of this building material are largely influenced by the fibre orientation. Therefore information on the fibre orientation is highly desirable. Computed tomography measurements allow for the non destructive investigation of the material. The contrast between fibres and concrete matrix is sufficiently high, even for glass fibres. Two different ways to study the fibre orientation are compared. The results correlate with the strength and the deformation behaviour of the samples. A high resolution study of the fibre environment shows that the fibres align the adjacent pores.
Proceedings of SPIE | 2007
Alexander Rack; Michael Stiller; Christine Knabe; Olaf Dalügge; Ch. Koch; Gerd Weidemann; Heinrich Riesemeier; Jürgen Goebbels
This article presents a novel approach to evaluate two-dimensional histomorphometric studies of biodegradable ceramic particles by means of element-sensitive, three-dimensional and non-destructive synchrotron-microtomography (SCT). An in vivo study was performed in which bone substitute materials (Cerasorb) were implanted in the mandible to support the bone regeneration. After 6 months of implantation samples were prepared and investigated using SCT and subsequent 3D image analysis as well as histological evaluation. A comparison of corresponding tomographical and histological slices delivers information about the newly formed bone and its stage of development. Additionally SCT gives insights into the structural changes of the bony tissue in a given defect and the local biodegradation of the bone substitute material in a three-dimensional manner. This emphasizes the fact that the completion of investigations by 2D histological images with 3D tomographical images is required in order to be able to draw conclusions concerning the influence of different bioceramics on the bone regeneration.
Tm-technisches Messen | 2008
Michael Neugebauer; Uwe Hilpert; Markus Bartscher; Norbert Gerwien; Michael Krystek; Carsten Schwehn; Michael Trenk; Jürgen Goebbels; Gerd Weidemann
Es werden Untersuchungen beschrieben, um mit großen taktilen Koordinatenmessgeräten (KMG) Mikrogeometrien zu messen. Der Einfluss der Antastkraft wird experimentell untersucht und der Einfluss der Formabweichungen auf die Messunsicherheit ermittelt. Am Beispiel eines Prüfkörpers für Mikrocomputertomographiemesssysteme (μCT) werden die Ergebnisse taktiler Messungen mit unterschiedlichen KMGs sowie mit einem μCT-Messsystem verglichen. Investigations are described to measure micro-geometries by means of a large tactile coordinate measuring machine (CMM). The influence of the contacting force is investigated experimentally and the influence of form deviations on the measurement uncertainty is determined. At the example of a standard for micro computed tomography (μCT) the measurement results of different tactile CMMs and a μCT are compared.
Materials Testing-Materials and Components Technology and Application | 2006
Markus Bartscher; Uwe Hilpert; Jürgen Goebbels; Gerd Weidemann; Holm Puder; Horia-Nicolae Jidav
Kurzfassung Unter vollständigem Reverse-Engineering (RE) versteht man die physische Rekonstruktion eines Bauteils ohne Kenntnis seiner Konstruktionsdaten. Am Anfang einer vollständigen Reverse-Engineering-Prozesskette steht das Originalbauteil, am Ende seine physische Kopie. Sollen auch innere Bauteilgeometrien erfasst werden, ist Computertomographie (CT) mit Röntgenstrahlen ein wesentlicher Bestandteil dieser Prozesskette. In diesem Beitrag wird am Beispiel eines Zylinderkopfes — einer historischen Motorkomponente eines Horch 853 Automobils von 1935—37 — eine vollständige RE-Prozesskette dargestellt und der Einfluss der verschiedenen Prozessschritte auf die Rekonstruktion des Originalteils untersucht. Die Prozesskette besteht aus der Bestimmung von äußeren und inneren Geometrien durch optische und CT-Messtechnik, der Verschmelzung der Ausgangsmessdaten zu einem einzigen Multisensordatensatz und dem Erstellen des virtuellen Modells, d.h. eines geeigneten Konstruktionsdatensatzes als Ausgangsbasis für die Fertigung der Bauteilkopien. Die Fertigung baut hier auf weiteren abgeleiteten Datensätzen auf, die gießtechnische sowie Bearbeitungsmodifikationen enthalten. Durch die notwendige Adaption an moderne Fertigungstechniken beinhaltet die Rekonstruktion eines historischen Bauteils immer auch eine partielle Umkonstruktion. Der originale Zylinderkopf diente als Vorlage für ein virtuelles Modell, von dem mehrere Kopien aus unterschiedlichen Materialien (Grauguss, Aluminium) angefertigt wurden. Der Beitrag stellt die angewandte, optimierte Prozesskette dar.
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment | 2008
Alexander Rack; S. Zabler; Bernd R. Müller; Heinrich Riesemeier; Gerd Weidemann; A. Lange; Jürgen Goebbels; M.P. Hentschel; W. Görner
Cirp Annals-manufacturing Technology | 2007
Markus Bartscher; Uwe Hilpert; Jürgen Goebbels; Gerd Weidemann
Archive | 2006
Alexander Rack; Christine Knabe; Michael Stiller; Christian Koch; Simon Zabler; Gerd Weidemann