NachhaltigElektrotechnik und MedientechnikMaschinenbau und MechatronikZeitschriftenartikel
L. Larcher, F. Puglisi, L. Jiang, Jonas Weber, Günther Benstetter, P. Pavan, M. Lanza, Werner Frammelsberger
Understanding Current Instabilities in Conductive Atomic Force Microscopy
Materials, vol. 12, no. 3
2019
DOI: 10.3390/ma12030459
Abstract anzeigen
Conductive atomic force microscopy (CAFM) is one of the most powerful techniques in studying the electrical properties of various materials at the nanoscale. However, understanding current fluctuations within one study (due to degradation of the probe tips) and from one study to another (due to the use of probe tips with different characteristics), are still two major problems that may drive CAFM researchers to extract wrong conclusions. In this manuscript, these two issues are statistically analyzed by collecting experimental CAFM data and processing them using two different computational models. Our study indicates that: (i) before their complete degradation, CAFM tips show a stable state with degraded conductance, which is difficult to detect and it requires CAFM tip conductivity characterization before and after the CAFM experiments; and (ii) CAFM tips with low spring constants may unavoidably lead to the presence of a ~1.2 nm thick water film at the tip/sample junction, even if the maximum contact force allowed by the setup is applied. These two phenomena can easily drive CAFM users to overestimate the properties of the samples under test (e.g., oxide thickness). Our study can help researchers to better understand the current shifts that were observed during their CAFM experiments, as well as which probe tip to use and how it degrades. Ultimately, this work may contribute to enhancing the reliability of CAFM investigations.
DigitalMaschinenbau und MechatronikBeitrag (Sammelband oder Tagungsband)
Gabriel Herl, Jochen Hiller, A. Stock, T. Sauer
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.
DigitalMaschinenbau und MechatronikBeitrag (Sammelband oder Tagungsband)
Gabriel Herl, Jochen Hiller, A. Stock, T. Sauer
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.
NachhaltigMaschinenbau und MechatronikBeitrag (Sammelband oder Tagungsband)
T. Wagner, S. Leyer, Giuseppe Bonfigli, Nadine Kaczmarkiewicz
Performance of the Passive Core Flooding System in the Integral Tests of the Project EASY
49. Jahrestagung Kerntechnik / 49th Annual Meeting on Nuclear Technology (AMNT 2018), Berlin , 29. - 30. Mai 2018
2018
Abstract anzeigen
Among nuclear power generation plants, light water reactors are mainly used at present, and are anticipated to be predominant in the future. To improve the light water reactors the development of the LWRs for the next generation is carried out at various organizations. For example, in the USA the Westinghouse AP-1000 is based on proven technology but with an emphasis on passive safety features. The reactor passive core cooling systems include the core makeup tanks system, passive residual heat removal heat exchanger and in-containment refuelling water storage tank. In Russia has been developed the so-called NPP-2006 project of a VVER-1200 nuclear power plant with a V-392M reactor unit. To provide the safety, protection passive systems which don’t depend upon human errors are widely used in this project. Among these are hydrotanks of the second stage and passive heat removal system. In the presented paper an overview of passive core cooling systems for next generation NPPs is given.
DigitalMaschinenbau und MechatronikZeitschriftenartikel
Mario Salzinger, Jochen Hiller, Thomas Fischer, Daniel Heinz
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.
NachhaltigMaschinenbau und MechatronikBeitrag (Sammelband oder Tagungsband)
T. Wagner, N. Neukam, Giuseppe Bonfigli, Nadine Kaczmarkiewicz, S. Buchholz, F. Schäfer, W. Klein-Hessling
The Code System AC2 for the Simulation of Advanced Reactors within the Frame of the German EASY Project
Proceedings of the 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17) [September 3-8, 2017; Qujiang Int’l Conference Center, Xi’an, Shaanxi, China]
2017
NachhaltigMaschinenbau und MechatronikBeitrag (Sammelband oder Tagungsband)
T. Wagner, N. Neukam, Giuseppe Bonfigli, Nadine Kaczmarkiewicz, S. Buchholz, F. Schäfer, A. Schaffrath
Evidence of Design Basis Accidents Mitigation Solely with Passive Safety Systems within the Frame of the German EASY Project
Proceedings of the 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17) [September 3-8, 2017; Qujiang Int’l Conference Center, Xi’an, Shaanxi, China]
2017
NachhaltigMaschinenbau und MechatronikBeitrag (Sammelband oder Tagungsband)
T. Wagner, S. Leyer, Giuseppe Bonfigli, Nadine Kaczmarkiewicz
Influence of Two-Phase Reverse Flow in the Passive Core Flooding System: Experiments and Simulations within the Frame of the German EASY Project
Proceedings of the 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17) [September 3-8, 2017; Qujiang Int’l Conference Center, Xi’an, Shaanxi, China]
2017
NachhaltigElektrotechnik und MedientechnikMaschinenbau und MechatronikZeitschriftenartikel
M. Nafría, Tobias Berthold, Günther Benstetter, R. Rodríguez, Werner Frammelsberger
Numerical Study of Hydrodynamic Forces for AFM Operations in Liquid Scanning (Article ID 6286595, 12 pages)
Scanning, pp. 1-12
2017
DOI: 10.1155/2017/6286595
Abstract anzeigen
For advanced atomic force microscopy (AFM) investigation of chemical surface modifications or very soft organic sample surfaces, the AFM probe tip needs to be operated in a liquid environment because any attractive or repulsive forces influenced by the measurement environment could obscure molecular forces. Due to fluid properties, the mechanical behavior of the AFM cantilever is influenced by the hydrodynamic drag force due to viscous friction with the liquid. This study provides a numerical model based on computational fluid dynamics (CFD) and investigates the hydrodynamic drag forces for different cantilever geometries and varying fluid conditions for Peakforce Tapping (PFT) in liquids. The developed model was verified by comparing the predicted values with published results of other researchers and the findings confirmed that drag force dependence on tip speed is essentially linear in nature. We observed that triangular cantilever geometry provides significant lower drag forces than rectangular geometry and that short cantilever offers reduced flow resistance. The influence of different liquids such as ultrapure water or an ethanol-water mixture as well as a temperature induced variation of the drag force could be demonstrated. The acting forces are lowest in ultrapure water, whereas with increasing ethanol concentrations the drag forces increase.
DigitalMaschinenbau und MechatronikZeitschriftenartikel
N. Sawczyn, D. Imkamp, Jochen Hiller, E. Uhlmann
Untersuchungen zur Messunsicherheit und Wirtschaftlichkeit dimensioneller Computertomographie-Messungen an ausgewählten Beispielen
tm - Technisches Messen, vol. 84, no. 5, pp. 336-347
2017
Abstract anzeigen
Die industrielle Computertomographie (CT) wird zunehmend für die zerstörungsfreie Prüfung von Bauteilen als Instrument der fertigungsbegleitenden Qualitätssicherung eingesetzt. Ein Vorteil gegenüber taktilen oder optischen Messverfahren ist insbesondere die Möglichkeit, sowohl außen- als auch innenliegende Geometriemerkmale zerstörungsfrei zu erfassen. In diesem Beitrag werden anhand ausgewählter Bauteile Möglichkeiten zur Steigerung der Wirtschaftlichkeit von CT-Messungen durch gleichzeitige tomographische Erfassung mehrerer Bauteile im Messvolumen untersucht und die Messunsicherheit für die einzelnen Aufnahmeszenarien experimentell ermittelt.
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