Publikationen


Suche nach „[Jochen] [Hiller]“ hat 72 Publikationen gefunden
Suchergebnis als PDF
    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Zeitschriftenartikel

    Jochen Hiller

    Computertomographie (CT) senkt Kosten bei der Retourenbearbeitung

    Sensorik-Magazin des Clusters Sensorik Strategische Partnerschaft Sensorik e.V., vol. 99, no. 4, pp. 3-5

    2020

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Zeitschriftenartikel

    F. Heilmeier, R. Koos, M. Singer, C. Bauer, Peter Hornberger, Jochen Hiller, W. Volk

    Evaluation of Strain Transition Properties between Cast-In Fibre Bragg Gratings and Cast Aluminium during Uniaxial Straining

    Sensors, vol. 20, no. 21

    2020

    DOI: 10.3390/s20216276

    Abstract anzeigen

    Current testing methods are capable of measuring strain near the surface on structural parts, for example by using strain gauges. However, stress peaks often occur within the material and can only be approximated. An alternative strain measurement incorporates fibre-optical strain sensors (Fiber Bragg Gratings, FBG) which are able to determine strains within the material. The principle has already been verified by using embedded FBGs in tensile specimens. The transition area between fibre and aluminium, however, is not yet properly investigated. Therefore, strains in tensile specimens containing FBGs were measured by neutron diffraction in gauge volumes of two different sizes around the Bragg grating. As a result, it is possible to identify and decouple elastic and plastic strains affecting the FBGs and to transfer the findings into a fully descriptive FE-model of the strain transition area.We thus accomplished closing the gap between the external load and internal straining obtained from cast-in FBG and generating valuable information about the mechanisms within the strain transition area.It was found that the porosity within the casting has a significant impact on the stiffness of the tensile specimen, the generation of excess microscopic tensions and thus the formation of permanent plastic strains, which are well recognized by the FBG. The knowledge that FBG as internal strain sensors function just as well as common external strain sensors will now allow for the application of FBG in actual structural parts and measurements under real load conditions. In the future, applications for long-term monitoring of cast parts will also be enabled and are currently under development.

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Zeitschriftenartikel

    Jochen Hiller, Peter Landstorfer, Philipp Marx, Matthias Herbst

    Evaluation of the impact of faulty scanning trajectories in robot-based x-ray computed tomography

    Measurement Science and Technology, vol. 32, no. 1

    2020

    DOI: 10.1088/1361-6501/abaf2a

    Abstract anzeigen

    X-ray computed tomography (CT) imaging for industrial applications is limited to certain physical conditions to be fulfilled. The size of the measuring object and the accumulated wall thickness are two fundamental conditions. An omission of these conditions by not capturing object attenuation information by the x-ray detector leads to missing data in the 3D reconstruction process and results as a consequence in image degradation and artifacts. Conventional industrial x-ray CT is based on cone-beam projections and circular or helical scanning trajectories using linear axis and a rotary (lift) table. For many inspection tasks on big-sized or unusually shaped objects the physical limits for obtaining a sufficient high image quality are reached very quickly when using conventional CT systems. Industrial six-axis robots offer much more flexibility with respect to the conditions mentioned earlier and can overcome the limitations of conventional scanners. In the present work we characterized an industrial six-axis robot in its working space following ISO 9283 in terms of pose accuracy and pose repeatability. These results are then used to simulate faulty scanning trajectories in terms of pose deviations where a single robot is used as an object manipulator to rotate virtual specimens on a circular trajectory resulting in different (faulty) reconstruction datasets. These datasets are evaluated visually and by using performance parameters and geometrical features in order to determine the reproduction fidelity (performance) of a one arm robot-based CT system depending on different pose errors. With the results obtained it was shown that a robot-based CT system of type B (in our classification scheme) using one robot as object manipulator should be able to reach a spatial resolution power in the range of the voxel size (in our case 200 µm) and smaller (neglecting effects from focal spot size, detector unsharpness from x-ray to light conversation and scatter radiation) if systematic pose errors are compensated using appropriate calibration methods.

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Zeitschriftenartikel

    S. Zabler, M. Maisl, Peter Hornberger, Jochen Hiller, C. Fella, R. Hanke

    X-ray imaging and computed tomography for engineering applications

    tm - Technisches Messen, vol. 87, no. Online veröffentlicht: 08.04.2020

    2020

    DOI: 10.1515/teme-2019-0151

    Abstract anzeigen

    After an incremental development which took place over four decades, X-ray imaging has become an important tool for non-destructive testing and evaluation. Computed Tomography (CT) in particular beholds the power of determining the location of flaws and inclusions (e. g. in castings and composites) in three-dimensional object coordinates. Therefore, and thanks to a speed-up of the measurement, CT is now routinely considered for in-line inspection of electronics, castings and composites. When precision and not speed is important, Micro-CT (μCT) can be employed for Dimensional Measurements (DM, e. g. quality assurance and shape verification), as well as for in situ testing, and for characterizing micro-structures in metals and composites. Using appropriate image processing and analysis μCT can determine the local fibre orientation in composites, the granular morphology of battery cathodes or the inter-connectivity of certain phases in casting alloys. Today, the large variety of X-ray instruments and methods poses an application problem which requires experience and a lot of knowledge for deciding which technique applies best to the task at hand. Application-specific guidelines exist for X-ray radiography testing (RT) only, whereas standardization has been applied to CT, unfortunately leaving out high resolution subμ CT, and nano-CT. For the latter exist an equally high number of NDT applications, however these instruments still necessitate a profound expertise. The task is to identify key industrial applications and push CT from system standardization to application specific automation.

    DigitalNachhaltigF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Zeitschriftenartikel

    Gabriel Herl, Jochen Hiller, A. Maier

    Scanning trajectory optimisation using a quantitative Tuybased local quality estimation for robot-based X-ray computed tomography

    Nondestructive Testing and Evaluation, vol. (Published 21 June 2020), no. 6, pp. 1-17

    2020

    DOI: 10.1080/10589759.2020.1774579

    Abstract anzeigen

    Robotic CT systems allow complex scanning trajectories. This work presents a workflow to automatically calculate optimised scanning trajectories for robotic CT systems. In particular, as a local quality estimation, this work introduces a quantitative measure to quantify local reconstruction quality based on the Tuy conditions. The proposed method is tested in two summation experiments using an STL model of a motorcycle. In both experiments, a trajectory is calculated using a quantitative Tuy-based local quality estimation and the reconstruction result is then compared to reconstructions using conventional scanning trajectories. The comparison results indicate that the proposed approach automatically finds trajectories that enable 3D reconstructions with high image quality using much less projection data, which allows a significant reduction of scanning time.

    DigitalNachhaltigF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Zeitschriftenartikel

    A. Stock, Gabriel Herl, T. Sauer, Jochen Hiller

    Edge-preserving compression of CT scans using wavelets

    Insight - Non-Destructive Testing and Condition Monitoring (The British Institute of Non-Destructive Testing), vol. 62, no. 6, pp. 345-351

    2020

    DOI: 10.1784/insi.2020.62.6.345

    Abstract anzeigen

    This work addresses the subject of efficient storage of computed tomography (CT) data with an emphasis on the quality of surfaces. Industrial dimensional metrology often requires high measurement accuracy and it is shown that this is retained using wavelet-based compression methods. The applied techniques include a tensor product wavelet transform and soft wavelet shrinkage. In these tests, performed on real objects, dimensional CT measurements of compressed and uncompressed volumes were compared. The necessary storage space was reduced significantly with a negligible loss of accuracy. The storage space required for a multi-sphere phantom was decreased to 4.7% (from 638 MB to 30 MB), with an average deviation below 1 μm from the original volume.

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Zeitschriftenartikel

    F. Heilmeier, R. Koos, Peter Hornberger, Jochen Hiller, K. Weraneck, M. Jakobi, A. Koch, W. Volk

    Calibration of cast-in Fibre-Bragg-Gratings for internal strain measurements in cast aluminium by using neutron diffraction

    Measurement, vol. 163, no. 15 October 2020

    2020

    DOI: 10.1016/j.measurement.2020.107939

    Abstract anzeigen

    Fibre Bragg gratings (FBGs) are utilized to function as internal strain sensors during casting, solidification and cooling of two hypoeutectic Al alloys and technically pure Al. In situ neutron diffraction experiments were conducted simultaneously onsite the STRESS-SPEC instrument at the Research-Neutron Source (MLZ) in Garching. The experimental data correlated with structural finite element simulation and X-ray micro tomography (CT) elucidates the mechanisms of this measurement system. The presented work offers a new practical approach to measure in-situ strains during casting of Al alloys by using FBG-based sensors. The FBG strain results correlate with the Al(311) peak obtained by neutron diffraction which is furthermore used for calibration. The examination of interactions between fibres and surrounding cast Al by finite element simulation and CT of the cast specimens enables the application of the sensors for unequivocal strain measurements in castings as well as the characterization of alloys during solidification.

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Beitrag (Sammelband oder Tagungsband)

    Peter Landstorfer, Gabriel Herl, Jochen Hiller

    Investigation of Non-circular Scanning Trajectories in Robot-based Industrial X-ray Computed Tomography of Multi-material Objects

    16th International Conference on Informatics in Control, Automation and Robotics (ICINCO) [29-31 July, 2019; Prague, Czech Republic]

    2019

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Beitrag (Sammelband oder Tagungsband)

    Peter Landstorfer, Jochen Hiller, Matthias Herbst

    Investigation of positioning accuracy of industrial robots for robotic-based X-ray computed tomography

    iCT 2019 9th Conference on Industrial Computed Tomography (iCT) [13-15 February, 2019; Padua, Italy]

    2019

    Abstract anzeigen

    In this research work we investigated the accuracy of a standard industrial robot. We wanted to find out, how accurate an X-RayComputed Tomography (CT) scan can be performed when using such a robot as a manipulator. The accuracy was measuredusing a laser-interferometer. The measured deviations were used to run an X-Ray simulation via Fraunhofer EZRT’s ScorpiusX-Lab. Metrological analysis was performed as a measure for the quality of the simulated CT-scan. The metrological deviationsreflect the feasible accuracy of a CT-scan in a real CT-setup.

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Beitrag (Sammelband oder Tagungsband)

    Gabriel Herl, Jochen Hiller, T. Sauer

    Artifact reduction in X-ray computed tomography by multipositional data fusion using local image quality measures

    iCT 2019 9th Conference on Industrial Computed Tomography (iCT) [13-15 February, 2019; Padua, Italy]

    2019

    Abstract anzeigen

    Metal artifacts are still a major problem in X-ray industrial computed tomography. In order to reduce metal artifacts and increase the image quality of X-ray CT-scans, we suggest using projection data from multiple scans with differently positioned object orientations. We present two different approaches for multipositional CT, which are especially effective for multimaterial objects with high absorbing metal parts. On one hand, we reconstruct the different scans separatly, estimate the local quality of the resulting volumes and then fuse these volumes to an optimized volume. On the other hand, we introduce smART (shrinking merged Algebraic Reconstruction Technique) and merge sinograms of different scans, estimate the reliability of each projection pixel and then reconstruct the merged sinogram with an adapted SART reconstruction method. We demonstrate our approaches on simulations and on measurement data and are able to show a significant reduction of image artifacts qualitatively and quantitatively with the help of dimensional measurement results.

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Zeitschriftenartikel

    Gabriel Herl, Jochen Hiller, S. Kasperl, A. Maier

    Reduktion von Metallartefakten durch multipositionale Datenfusion in der industriellen Röntgen-Computertomographie

    tm - Technisches Messen, vol. 87, no. 2

    2019

    DOI: 10.1515/teme-2019-0137

    Abstract anzeigen

    Metallartefakte stellen eine große Herausforderung für das Messen mit Röntgen-Computertomographie dar. Dieser Beitrag stellt die Methode der multipositionalen Datenfusion zur Reduktion von Metallartefakten vor. Dazu werden mehrere Scans desselben Objekts bei unterschiedlicher Objekt-positionierung durchgeführt, aufeinander registriert und zur Fusion gemeinsam unter Betrachtung eines lokalen Gütemaßes rekonstruiert. In praxisnahen Experimenten wird der Mehrwert der Methode gezeigt. Insbesondere wird dargestellt, wie mit wenig Aufwand und ohne Vorwissen Kunststoffstrukturen trotz starker Metallartefakte sichtbar gemacht werden können, womit das Verfahren ein Alleinstellungsmerkmal gegenüber den existierenden Metallartefaktreduktionsverfahren aufweist.

    DigitalNachhaltigF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Zeitschriftenartikel

    Peter Hornberger, A. Sigl, Jochen Hiller, S. Zabler

    Kleiner als ein Mikrometer: Entwicklung einer kompakten, hochauflösenden 3D-Röntgen-CT für die Materialanalyse

    VDI-Z (Sonderteil Additive Fertigung)

    2019

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Beitrag (Sammelband oder Tagungsband)

    Borges de Oliveira, F., M. Bartscher, U. Neuschaefer-Rube, R. Tutsch, Jochen Hiller

    Multi-Material Acceptance Testing for CT-Based Coordinate Measurement Systems

    Proceedings of the 12th International Conference on Measurement and Quality Control

    2019

    ISBN: 3030181766

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Beitrag (Sammelband oder Tagungsband)

    A. Stock, Gabriel Herl, T. Sauer, Jochen Hiller

    Edge preserving compression of CT scans using wavelets

    SHM-NDT 2018 International Symposium on Structural Health Monitoring and Nondestructive Testing 4-5 Oct 2018, Saarbrücken – Germany

    2018

    Abstract anzeigen

    This work addresses the subject of efficient storage of computed tomography (CT) data with an emphasis on the quality of surfaces. Industrial dimensional metrology often requires high measurement accuracy and we show that this is retained using wavelet-based compression methods. The applied techniques include a tensor product wavelet transform and soft wavelet shrinkage. In our tests on real objects, we compared dimensional CT measurements of compressed and uncompressed volumes. We were able to reduce the necessary storage space significantly with a minimal loss of accuracy. For a multi sphere phantom, we decreased the storage space to 4.7% (from 638 MB to 30 MB) with an average deviation below 1 µm from the original volume.

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Beitrag (Sammelband oder Tagungsband)

    A. Stock, Gabriel Herl, T. Sauer, Jochen Hiller

    Metal artifact reduction by fusion of CT scans from different positions using the unfiltered backprojection

    iCT 2018 8th Conference on Industrial Computed Tomography (iCT) 2018, 6-9 Feb, Wels, Austria

    2018

    Abstract anzeigen

    Metal objects or metal parts in an object are still a major problem of X-ray computed tomography (CT) because of so called metal artifacts. We propose a new method – a multipositional data fusion – for automatically fusing multiple CT volumes from different positions to reduce these metal artifacts. After scanning a specimen several times at different positions and reconstruction of every scan (e.g. by the filtered backprojection), we also perform an unfiltered backprojection. Based on the assumption that metal artifacts occur the most wherever X-rays are attenuated a lot, the unfiltered backprojection is used to autonomously estimate the likelihood of metal artifacts in every voxel of every scan. The different volumes are registered and then fused by weighted sum preferring the voxels with low values in the unfiltered backprojection results. In our tests on real objects, our method fully automatically created optimized volumes with significantly less metal artifacts. The multipositional data fusion was compared to the commercially multi spectra fusion of Werth Messtechnik GmbH and outperformed it in one of the use cases.

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Vortrag

    Gabriel Herl, Simon Rettenberger, Jochen Hiller, T. Sauer

    Metal artifact reduction by fusion of CT scans from different positions using the unfiltered backprojection

    8th Conference on Industrial Computed Tomography (iCT 2018), Wels, Österreich

    2018

    Abstract anzeigen

    Metal objects or metal parts in an object are still a major problem of X-ray computed tomography (CT) because of so called metal artifacts. We propose a new method – a multipositional data fusion – for automatically fusing multiple CT volumes from different positions to reduce these metal artifacts. After scanning a specimen several times at different positions and reconstruction of every scan (e.g. by the filtered backprojection), we also perform an unfiltered backprojection. Based on the assumption that metal artifacts occur the most wherever X-rays are attenuated a lot, the unfiltered backprojection is used to autonomously estimate the likelihood of metal artifacts in every voxel of every scan. The different volumes are registered and then fused by weighted sum preferring the voxels with low values in the unfiltered backprojection results. In our tests on real objects, our method fully automatically created optimized volumes with significantly less metal artifacts. The multipositional data fusion was compared to the commercially multi spectra fusion of Werth Messtechnik GmbH and outperformed it in one of the use cases.

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Vortrag

    A. Stock, Gabriel Herl, T. Sauer, Jochen Hiller

    Edge preserving compression of CT scans using wavelets

    International Symposium on Structural Health Monitoring and Nondestructive Testing, Saarbrücken

    2018

    Abstract anzeigen

    This work addresses the subject of efficient storage of computed tomography (CT) data with an emphasis on the quality of surfaces. Industrial dimensional metrology often requires high measurement accuracy and we show that this is retained using wavelet-based compression methods. The applied techniques include a tensor product wavelet transform and soft wavelet shrinkage. In our tests on real objects, we compared dimensional CT measurements of compressed and uncompressed volumes. We were able to reduce the necessary storage space significantly with a minimal loss of accuracy. For a multi sphere phantom, we decreased the storage space to 4.7% (from 638 MB to 30 MB) with an average deviation below 1 µm from the original volume.

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Zeitschriftenartikel

    Thomas Fischer, Mario Salzinger, Daniel Heinz, Jochen Hiller

    Quantitative Untersuchung zur Reduzierung der Messzeit in der dimensionellen Computertomographie

    Bavarian Journal of Applied Sciences, vol. 3, no. 1, pp. 282-296

    2017

    DOI: 10.25929/jy3v-pm72

    Abstract anzeigen

    Einer der häufig genannten Nachteile für Computertomographie-(CT-)Anwender in der industriellen Praxis ist der Zeitfaktor. Für einen messtechnisch auswertbaren CT-Scan ist das System in den meisten Fällen mindestens 30 Minuten lang ausgelastet, je nach Prüfobjekt und Genauigkeitsanforderungen oft auch deutlich länger. Ziel dieser Untersuchung ist es, mit derzeitig möglichen Methoden herauszufinden, wie die Scanzeiten verringert werden können und wie sich diese Reduzierung auf die Qualität der Messung bezüglich Messgenauigkeit und Wiederholgenauigkeit auswirkt. Nach Auswahl und taktiler Referenzmessung eines Prüfkörpers werden mit dem 360° Stop&Go-Verfahren sowie mit zwei weiteren Scanstrategien, der 180° CT und der FlyBy-CT, Messdaten erzeugt. Es folgt ein Vergleich der Messergebnisse und der Messzeiten. Bei der 180°-Messung wird das Objekt intermittierend um die Hälfte rotiert, wohingegen beim FlyBy-Modus eine kontinuierliche Objektbewegung ohne Abbremsung erfolgt. Beide Messverfahren haben sich für diverse Anwendungsszenarien bewährt. Die größte Messzeitreduzierung ist beim Einsatz des FlyBy-Modus zu erwarten. Im Vergleich dazu bietet der 180°-Modus ebenfalls Vorteile, auch wenn die erwartete Scanzeit gegenüber dem FlyBy-Modus länger ist. Mit diesem lässt sich trotz der Möglichkeit zur Bildmittelung Scanzeit einsparen, gegenüber dem herkömmlichen 360°-Scanverfahren lässt sich aber zudem bei gleichbleibender Zeit eine erhöhte Rauschreduzierung erzielen. One of the biggest disadvantages operators complain about in the field of industrial computed tomography is the time factor. CT scans for measuring purposes will usually take at least 30 minutes, yet often noticeably longer, depending on the specimen and accuracy requirements. The purpose of this research is to determine how scan times can be reduced by applying the currently available methods and to assess in which way this reduction influences measurement quality with regards to measurement accuracy and repeatability. After choosing a test specimen and performing tactile measurements to determine the nominal values, measurement data is generated by using the 360° Stop&Go procedure, the 180° CT and the FlyBy-CT. Then the measurement results and durations are compared with each other. Measurements using the 180° procedure are performed by intermittently rotating the object by 180 degrees, whereas the FlyBy mode involves a continuous object movement without deceleration. Both CT modes are well proven in various applications. Out of all three methods, the FlyBy mode has the greatest potential for reducing overall scan times. In comparison, the 180° mode also has its advantages, although the expected scan times are longer compared to the FlyBy mode. This CT mode offers the opportunity to reduce scan times despite the option of image averaging. In addition, compared to the conventional 360° scan procedures, it is possible to achieve a higher level of noise reduction within a constant time.

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Beitrag (Sammelband oder Tagungsband)

    Peter Hornberger, Christian Aichinger, Jochen Hiller

    Dimensionelles Messen mit Computertomographie

    Handbuch zur industriellen Bildverarbeitung. Qualitätssicherung in der Praxis

    2017

    ISBN: 978-3-8396-1226-2

    DigitalF: Maschinenbau und MechatronikI: Fraunhofer AWZ CTMT

    Beitrag (Sammelband oder Tagungsband)

    Jochen Hiller, Peter Hornberger, Thomas Miller

    Dimensional Metrology for Industrial Computed Tomography

    Handbook of X-ray Imaging - Physics and Technology, Boca Raton, FL, USA

    2017

    ISBN: 9781498741521