Juergen Goebbels - Academia.edu (original) (raw)

Papers by Juergen Goebbels

Due to the progress in Computed Tomography (CT) applied for dimensional control new fields in ma-... more Due to the progress in Computed Tomography (CT) applied for dimensional control new fields in ma-terials characterization are opened. Especially volume properties can be non-destructively and quantita-tively analysed which are non-accessible by other methods. These possibilities are used to study time dependent properties of corrosion. As an example concrete cylinders with embedded steel bars as working electrode are investigated. The mass loss of the working electrode is determined by CT and compared with results from electrochemical and gravimetric measurements. The limitations of the evaluation process of corrosion by CT are studied using a simulation program for the radiographic pro-jections. Introduction The progress in Computed Tomography (CT) applied for dimensional control, which has been reached in the last years, has opened new fields in materials characterization [1]. Especially volume properties can be non-destructively and quantitatively analysed which are non-accessibl...

X-ray computed tomography (CT) techniques have been used to evaluate a structural index of high p... more X-ray computed tomography (CT) techniques have been used to evaluate a structural index of high performance metal matrix composites (MMC). Beside of classical features like the determination of number of fibres and eccentricity of fibre bundles an order parameter can be defined and demonstrated for the SiC fibre arrangem ent in Ti-MMC, which can be used to assess these materials. The samples for the investigations have been provid ed by MTU Aero Engines. They consist of a titanium matrix (Ti6242) reinforced by SiC fibres ( SCS6).

Proceedings of SPIE - The International Society for Optical Engineering

Some very small parts from regular cellular (spherical) metals were investigated in a strength te... more Some very small parts from regular cellular (spherical) metals were investigated in a strength test, which was done inside the (mu) CT machine with resolutions down to 5 micrometers . The aim was to inspect the behavior of the walls of cellular metals under load, and to find out how the buckling or breaking starts. The results are needed for theoretical calculations, which will be used to predict the behavior of large structures of these materials. Also the pore size and pore size distribution for cellular metals is calculated and a method to separate walls and nodes is presented. CT insights of cellular metals as well as investigations of data by means of image processing is shown.

European cells & materials, Jan 30, 2004

Micro-computed tomography (microCT) provides quantitative three-dimensional information of bone a... more Micro-computed tomography (microCT) provides quantitative three-dimensional information of bone around titanium implants similar to classical histology. The study, based on an animal model, containing cuboid-shaped biofunctionalised Ti6Al4V implants with surrounding bone after 4 weeks, is performed using 3 microCT-systems with X-ray tubes, one synchrotron-radiation-based microCT-system (SRmicroCT), and classical histology. Although the spatial resolution of the microCT-systems is comparable, only the results of SRmicroCT agree with results of classical histology. The X-ray tube sources give rise to huge artefacts in the tomograms (interface scattering, beam hardening), which impaired the quantitative analysis of bone up to about 200microm from the implant surface. Due to the non-destructive character of microCT the specimens can be subsequently examined by classical histology without restriction. The quantitative comparison of bone formation uncovers the strong dependence of the new...

Volume 13: Processing and Engineering Applications of Novel Materials, 2007

Advanced structures (aircraft, wind turbine blades, automotive) made of composite materials have ... more Advanced structures (aircraft, wind turbine blades, automotive) made of composite materials have to endure high mechanical and environmental loading. Therefore the durability and reliability depends much more on the micro mechanical properties than on the global strength. Non-destructive testing methods based on X-ray radiation are powerful tools for the characterization of materials. Applied to fibre composites the method gives information about the fibre orientation, the fibre matrix debonding and the micro cracking due to mechanical loading. In the last 10 years several investigations were done at BAM to characterize composite materials from small scale as standard specimens up to complex components.

Developments in X-Ray Tomography III, 2002

ABSTRACT Some very small parts from regular cellular (spherical) metals were investigated in a st... more ABSTRACT Some very small parts from regular cellular (spherical) metals were investigated in a strength test, which was done inside the (mu) CT machine with resolutions down to 5 micrometers . The aim was to inspect the behavior of the walls of cellular metals under load, and to find out how the buckling or breaking starts. The results are needed for theoretical calculations, which will be used to predict the behavior of large structures of these materials. Also the pore size and pore size distribution for cellular metals is calculated and a method to separate walls and nodes is presented. CT insights of cellular metals as well as investigations of data by means of image processing is shown.

$Research paper thumbnail of <title>X-ray refraction topography and computed tomography for NDE of lightweight materials (Keynote Paper)</title>$

Testing, Reliability, and Application of Micro- and Nano-Material Systems III, 2005

X-Ray Refraction Topography techniques are based on Ultra Small Angle Scattering by micro structu... more X-Ray Refraction Topography techniques are based on Ultra Small Angle Scattering by micro structural elements causing phase related effects like refraction and total reflection at a few minutes of arc as the refractive index of X-rays is nearly unity (1x10-5). The extraordinary contrast of inner surfaces is far beyond absorption effects. Scanning of specimens results in 2D-imaging of closed and

Developments in X-Ray Tomography, 1997

Journal of Power Sources, 2009

731/9530 612, fax: +49/731/9530 666

European Journal of Entomology, 2006

Internal and external features of the head of Ascioplaga mimeta (Coleoptera: Archostemata) were s... more Internal and external features of the head of Ascioplaga mimeta (Coleoptera: Archostemata) were studied with micro X-ray computertomography (µCT) and nuclear magnetic resonance imaging (NMRI). These methods allowed the reconstruction of the entire internal anatomy from the only available fixed specimen. The mouthparts and their associated musculature are highly derived in many aspects. Their general configuration corresponds to that of Priacma serrata (the only other archostematan studied in comparable detail). However, the mandible-maxilla system of A. mimeta is built as a complex sorting apparatus and shows a distinct specialisation for a specific, but still unknown, food source. The phylogenetic analysis resulted in the identification of a new monophylum comprising the genera [Distocupes + (Adinolepis +Ascioplaga)]. The members of this taxon are restricted to the Australian zoogeographic region. The most prominent synapomorphies of these three genera are their derived mouthparts.

ABSTRACT An advantage of Computed Tomography (CT) is the coordinate measurement capability of sma... more ABSTRACT An advantage of Computed Tomography (CT) is the coordinate measurement capability of small inner structures, which are not accessible with classical measurement techniques. Using the advantages of synchrotron radiation CT measurements of parts with sizes of a few millimeters are performed at BAMline of BESSY II and are expected to be used as references for further dimensional measurements with micro CT. Previous investigations were focused on external gears, which are accessible with standard Coordinate Measurement Machines (CMMs). To obtain information about the accuracy of dimensional measurements of internal gears with CT, reference data have been measured by a tactile-optical CMM. This information is used to evaluate the performance of the CT. In addition to the first results for the evaluation of internal gear flanks, new measurements of different gear materials (steel and zirconium dioxide) will be presented. For functional evaluation, gear flanks are a matter of particular interest. Form deviations are analyzed with respect to the different gear materials to establish CT measurements as technology in the field of quality assurance and to compare the different manufacturing processes.

tm - Technisches Messen, 2008

Merging information from different measurement procedures enables consistent and extensive charac... more Merging information from different measurement procedures enables consistent and extensive characterization of 3D geometries and features. Methods of processing, merging, and analyzing multimodal measurement data are shown and used with exemplary ...

Three-Dimensional Imaging, Interaction, and Measurement, 2011

ABSTRACT Micro gears are applied in an increasing quantity in many applications. Therefore, preci... more ABSTRACT Micro gears are applied in an increasing quantity in many applications. Therefore, precise measurements are of growing importance to ensure their quality. This contribution describes the measurement of gears of a micro planetary gear set with a tactile probe, a tactile-optical probe, an optical sensor, and computed tomography (CT). For the tactile measurements, a high precision piezoresistive microprobe was used. A so-called fiber probe was applied for tactile-optical measurements. This probe applies image processing to determine the position of the tactile probing element. For all tactile and tactile-optical measurements, single point probing was used. The optical measurements were carried out with an imaging sensor based on focus variation. Due to limited accessibility, on some gears not all regions could be measured by the optical sensor and the tactile-optical probe. In contrast to this, with CT the whole part could be measured with high point density. We used a micro-CT system and carried out measurements with Synchrotron-CT. All the sensors used deliver measurement data in Cartesian coordinates. It is a challenge to transfer these data into coordinates in which gear parameters are defined. For this, special attention must be paid to the determination of the gear axis and to the orientation of the teeth. The applied procedures are detailed for different micro gears. The comparison between data of different measurements was carried out successfully. The deviations between the CT data and the tactile or tactile-optical data lie in the range of only a few micrometers.

physica status solidi (b), 1980

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2008

is furnished to the author for non-commercial research and education use, including for instructi... more is furnished to the author for non-commercial research and education use, including for instruction at the author's institution, sharing with colleagues and providing to institution administration.

Nondestructive Testing and Evaluation, 1992

Typical properties and defect structures in composites are well characterized by high resolution ... more Typical properties and defect structures in composites are well characterized by high resolution X-ray tomography. This NDE method can be particularly used in the development of materials to reduce time consuming methods like micrographs, if the time scale is appropriate even time dependent processes like a dry-up procedure can be studied by CT. For large components a Region-of-Interest method was

Materialwissenschaft und Werkstofftechnik, 2000