NachhaltigTC WeißenburgZeitschriftenartikel
Wang, J., Dmitry Rychkov, Q. Nguyen, Gerhard, R.
The influence of orthophosphoric-acid surface modification on charge-storage enhancement in polypropylene electrets
Journal of Applied Physics, vol. 128, no. 3
2020
DOI: 10.1063/5.0013805
Abstract anzeigen
Bipolar electrets from polypropylene (PP) are essential, e.g., in electret air filters and in cellular-foam ferroelectrets. Therefore, the mechanism of surface-charge stability enhancement on PP electrets via orthophosphoric-acid surface treatment is investigated in detail. It is shown that the significant charge-stability enhancement can be mainly attributed to deeper surface traps originating from deposited chemicals and topographic features on the modified surfaces. Thermally stimulated discharge of chemically treated and non-treated PP films with different surface-charge densities is used to test the limits of the newly formed deep traps in terms of the capacity for hosting surface charges. When the initial surface-charge density is very high, more charges are forced into shallower original traps on the surface or in the bulk of the treated PP samples, reducing the effect of the deeper surface traps brought by the surface modification. The well-known crossover phenomenon (of the surface-charge decay curves) has been observed between modified PP electrets charged to ±2 kV and to ±3
kV. Acoustically probed charge distributions in the thickness direction of PP electrets at different stages of thermal discharging indicate that the deep surface trapping sites may have preference for negative charges, resulting in the observed asymmetric charge stability of the modified PP films.
DigitalAngewandte WirtschaftswissenschaftenTC GrafenauVortrag
Diane Ahrens
Räumliche Unabhängigkeit Dank Digitalisierung
Sommerkolloquium 2020 der Bayerischen Akademie Ländlicher Raum und Akademie für Politik und Zeitgeschehen der Hanns-Seidel-Stiftung „Corona und die große Transformation: Perspektiven für die ländlichen Räume?“, München
2020
DigitalNachhaltigFraunhofer AWZ CTMTMaschinenbau und MechatronikZeitschriftenartikel
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
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.
DigitalNachhaltigFraunhofer AWZ CTMTMaschinenbau und MechatronikZeitschriftenartikel
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.
DigitalNachhaltigExternZeitschriftenartikel
Anton Schmailzl, Johannes Käsbauer, J. Martan, P. Honnerová, F. Schäfer, Maximilian Fichtl, T. Lehrer, L. Prušáková, J. Tesař, J. Skála, M. Honner
Measurement of core temperature through semi-transparent polyamide 6 using scanner-integrated pyrometer in laser welding
International Journal of Heat and Mass Transfer, vol. 146, no. January
2020
DOI: 10.1016/j.ijheatmasstransfer.2019.118814
Abstract anzeigen
Predicting the core temperature during welding is an ambitious aim in many research works. In this work, a 3D-scanner with integrated pyrometer is characterized and used to measure the temperature during quasi-simultaneous laser transmission welding of polyamide 6. However, due to welding in an overlap configuration, the heat radiation emitted from the joining zone of a laser transmission weld has to pass through the upper polymer, which is itself a semi-transparent emitter. Therefore, the spectral filtering of the heat radiation in the upper polymer is taken into account by calibrating the pyrometer for the measurement task. Thermal process simulations are performed to compare the temperature field with the measured temperature signal. The absorption coefficients of the polymers are measured, in order to get precise results from the computation. The temperature signals during welding are in good agreement with the computed mean temperature inside the detection spot, located in the joining area. This is also true for varying laser power, laser beam diameter and the carbon black content in the lower polymer. Both, the computed mean temperature and the temperature signal are representing the core temperature. In order to evaluate the spatial sensitivity of the measurement system, the emitted heat radiation from both polymers is calculated on basis of the computed temperature field. Hereby it is found, that more than 90 percent of the detected heat radiation comes from the joining area, which is a crucial information for contact-free temperature measurement tasks on semi-transparent polymers.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Sebastian Sitzberger, Johannes Liebl, Christian J. Trum, Rolf Rascher
Concept of a two-part clamping system for lenses in optical metrology
Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]), Bellingham, WA, USA
2020
DOI: 10.1117/12.2566547
Abstract anzeigen
The developed concept represents a universally applicable clamping system designed to fit in any measuring machine with
any measuring principle. The design ensures that, as long as the lens remains clamped, the measurement results are
reproducible. Form errors due to tension remain constant across all measuring and processing steps. The version presented
in this paper was developed especially for small lenses in the diameter range up to 40 mm. On the one hand, the design
allows for fast measurement of loose lenses. On the other hand, the device can also be used for measurement comparisons,
since lenses can also be mounted permanently. In the following, the concept and first results of measurement tests are
presented.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Armin Reif, Sebastian Sitzberger, Rolf Rascher
Cutting high-performance materials with ultrasonically modulated cutting speed
Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]), Bellingham, WA, USA
2020
DOI: 10.1117/12.2565757
Abstract anzeigen
The continuing trend towards lightweight construction and the associated machining rates of up to 95 % lead to an
increased use of high-performance materials. The ever growing demands on the strength and quality of components and
the associated use of materials which are hard to machine require the further development of new, economical machining
techniques. In ultrasonic-assisted machining, an additional high-frequency vibration is superimposed on the conventional
machining process. The vibration of the tool is usually excited axially or longitudinally to the workpiece, i.e. vertical to
the cutting direction. An additional vibration overlay around the rotation axis (torsional) of the tool is also possible. This
generates a vibration overlay in the cutting direction. The vibration initiation causes vibration amplitudes in the range of a
few micrometers at the tool cutting edge. This leads in turn to a high-frequency change in the cutting speed or feed rate.
Overall, an additional torsional vibration overlap can further reduce cutting forces, increase tool life and improve
workpiece quality.
In order for a grinding tool to generate a torsional vibration, a special tool was required that had to be designed by
simulation. The formation of a torsional vibration was achieved by helical slots in the sonotrode. Depending on the angle
of rotation and the length of the slots, a part of the axial vibration is converted into a torsional vibration by an axial
excitation of the sonotrode. The aim in designing the slots was to achieve the highest possible vibration amplitude.
Following the simulation, the slots were inserted into the tool in the corresponding optimum geometric position.
Afterwards, the specially designed grinding tool was validated by machining the brittle-hard glass-ceramic material
Zerodur. The first test results with the torsionally vibrating tool are presented in the following.
NachhaltigElektrotechnik und MedientechnikIQMAZeitschriftenartikel
H. Fan, Y. Zhang, D. Liu, C. Niu, L. Liu, W. Ni, Y. Xia, Z. Bi, Günther Benstetter, G. Lei
Tensile stress-driven cracking of W fuzz over W crystal under fusion-relevant He ion irradiations
Nuclear Fusion, vol. 60, no. 4
2020
DOI: 10.1088/1741-4326/ab71bb
Abstract anzeigen
Although W fuzz is formed in the divertor region of the fusion reactor, no theory may clearly explain the W fuzz growth mechanism. In this study, we observe the growth process of W fuzz over W crystal under ITER-relevant He ion irradiations. We propose the tensile stress-driven cracking of nano-structured fuzz during the initial growth of W fuzz. We demonstrate that the existence of tensile stress is due to the swelling of He nano-bubbles in the fuzz. After this cracking, the W fuzz breaks away from the planar network and grows over the W surface, where the micro-stress in the W surface layer acts as the driving force.
Elektrotechnik und MedientechnikZeitschriftenartikel
H. Heckelmüller, F. Kendl, Gerhard Krump
TDR Einzahlwert zur Charakterisierung der dynamischen Oberbausteifigkeit
ZEVrail - Zeitschrift für das gesamte System Bahn, vol. 144, no. Mai, pp. 190-194
2020
Abstract anzeigen
Der Schallmesswagen (SMW) der DB Systemtechnik prüft den akustischen Zustand des Oberbaus und wird vor allem zur Überprüfung von Streckenabschnitten mit der Maßnahme „Besonders überwachtes Gleis“ (BüG) verwendet. Zusätzlich wird der SMW zur Qualitätskontrolle und Abnahme des akustischen Schienenschleifens eingesetzt. Falls ein BüG-Abschnitt nicht vom SMW befahren werden kann, gilt seit 2001 die Ersatzmaßnahme RMF-BüG. Dieses Verfahren soll die Messaufgaben des SMW durch kontinuierliche Rauheitsmessungen beider Schienen ersatzweise übernehmen können. Beim RMF-BüG-Verfahren wurde zur Berechnung des SMW-Pegels ausschließlich die Schienenrauheit berücksichtigt. Anhand einer Vielzahl von Messungen konnte gezeigt werden, dass das Rollgeräusch des SMW signifikant ebenfalls von der Gleisabklingrate (Track Decay Rate TDR) abhängig ist. Das vorgestellte Verfahren zeigt die Verwendung des Einzahlwertes der Schienenrauheit LλCA und des Einzahlwertes der TDR L TDR zur Bestimmung des SMW-Pegels.
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