NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenTC Teisnach SensorikZeitschriftenartikel
F. Singer, Maria Kufner
Model based laser-ultrasound determination of hardness gradients of gas-carburized steel
NDT & E International, vol. 88, pp. 24-32
2017
DOI: 10.1016/j.ndteint.2017.02.006
Abstract anzeigen
Gas carburizing is a common industrial process utilized for case hardening of low carbon steels. However, thereis a lack of non-destructive evaluation systems for the measurement of hardness-depth profiles. We propose anovel measurement method for the determination of hardness-depth profiles of two-step gas carburized steelspecimens. The method is based on the measurement of broadband laser excited Rayleigh waves. Rayleighwaves were generated by a pulsed Nd: YAG laser in the thermoelastic regime and measured with a heterodyneMach-Zehnder interferometer in the near-field. From two measurements with different source to receiverdistances the dispersion diagrams were calculated by means of the phase spectral analysis method. In order tosimulate the observed dispersive behavior of the Rayleigh waves,first the two-step gas carburizing process wassimulated using solutions of the diffusion equation. The resulting continuous hardness profile was thendiscretized into up to 100 layers. Thereafter the Rayleigh wave dispersion diagram was calculated from thediscretized stack of layers using a delta-matrix formulation of the Thomson-Haskell transfer matrix method. Inorder to obtain bestfitting hardness profiles, the simulated dispersion diagrams werefitted to measurementswith a curvefitting algorithm. Comparison of the Rayleigh wave inversion method with destructively obtainedVickers hardness profiles shows good quantitative agreement.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenTC Teisnach SensorikBeitrag (Sammelband oder Tagungsband)
F. Brand, M. Gerbeth, F. Singer, Maria Kufner
Vergleich zwischen Laser-Doppler- und photorefraktivem Interferometer zur Messung von akustischen Oberflächenwellen unter industriellen Bedingungen
18. GMA/ITG - Fachtagung Sensoren und Messsysteme 2016
2016
ISBN: 978-3-9816876-0-6
DOI: 10.5162/sensoren2016/6.1.3
Abstract anzeigen
Laserbasierte-Ultraschall Verfahren werden unter Laborbedingungen bereits häufig verwendet, um Werkstoffeigenschaften zu ermitteln. Falls die zu vermessenden Proben jedoch eine diffuse Reflexion des Messlaserstrahls verursachen, treten häufig Probleme bei der Anwendbarkeit der laserbasierten Detektion auf. Ein zusätzliches Problem für die Anwendbarkeit von laserbasierten Ultraschall-Verfahren im industriellen Umfeld stellen niederfrequente Umgebungsschwingungen dar. Ein Interferometer mit photorefraktivem Kristall verspricht selbst bei einer Reflexion mit Speckle-Muster und Störschwingungen noch gute Signal-zu-Rausch-Verhältnisse. Ein Laser-Doppler-Vibrometer besitzt dagegen unter Laborbedingungen theoretisch eine niedrigere Detektionsgrenze, sofern eine gut reflektierende Probe sowie ausreichende Isolation von Störschwingungen vorhanden sind.
Im Rahmen dieser Arbeit wird ein selbst entwickeltes Interferometer mit photorefraktivem Kristall mit
einem Laser-Doppler-Vibrometer verglichen. Als Probe dient eine geschliffene Stahlprobe, die für die
optische Messung nicht speziell behandelt wurde.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenTC Teisnach SensorikZeitschriftenartikel
K. Schmidt, G. Lindner, Maria Kufner, J. Landskron
Stable vortex generation in liquid filled wells by mode conversion of surface acoustic waves
Physics Procedia, vol. 70, no. Proceedings of the 2015 ICU International Congress on Ultrasonics, Metz, France, pp. 98-101
2015
DOI: 10.1016/j.phpro.2015.08.051
Abstract anzeigen
The formation of stable vortex flow pattern has been observed at liquid filled aluminum wells of 15 to 30 mm diameter when Lamb waves are excited on the bottom of the wells by piezoelectric transducers operated at a frequency of 1 MHz. The shape of the vortex pattern changed with the position of the transducer. Strong differences in mixing times were observed between water and ethanol when the filling level was changed and a remarkable reduction of mixing time was achieved by the addition of a small amount of detergent to water at small filling levels. Besides mixing of liquids thermal equilibration within a liquid volume was accelerated by acoustic streaming.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenTC Teisnach SensorikZeitschriftenartikel
R. Baets, B. Dhoedt, I. Veretennicoff, G. Verschaffelt, H. Thienpont, S. Kufner, A. Van Hove, V. Baukens, P. Vynck, P. Tuteleers, H. Ottevaere, Maria Kufner, R. Bockstaele
Performances of optical multi-chip-module interconnects: comparing guided-Wave and free-space pathways
Journal of Optics A: Pure and Applied Optics, vol. 1, no. 2, pp. 255-261
1999
DOI: 10.1088/1464-4258/1/2/027
Abstract anzeigen
We simulate and compare optical transmission efficiencies, throughputs and interconnection lengths of free-space and POF-based guided-wave multi-chip-module optical interconnection demonstrators for different types of microcavity emitters.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenTC Teisnach SensorikZeitschriftenartikel
C. Debaes, R. Buczynski, I. Veretennicoff, G. Verschaffelt, J. Genoe, A. Hermanne, S. Kufner, V. Baukens, P. Vynck, P. Tutleers, H.Thienpont, H. Ottevaere, D. Coppée, Maria Kufner, S. Borghs, R. Vounckx
Demonstration of a Monolithic Multichannel Module for Multi-Gb/s Intra- MCM Optical Interconnects
IEEE Photonics Technology Letters, vol. 10, no. 11, pp. 1629-1631
1998
DOI: 10.1109/68.726772
Abstract anzeigen
In this letter, we report on the demonstration of a 2.48-Gb/s multichannel optical data-link for intramultichip module interconnects. The optical module was fabricated in polymethylmethacrylate (PMMA) by deep proton lithography and monolithically integrates micromirrors and cylindrical lenses. With the same technology, we have also fabricated a single-channel optical bridge and used this component to demonstrate a proof-of-principle optical intrachip interconnect by establishing a digital data-link between optoelectronic transceivers integrated on the same chip.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenTC Teisnach SensorikZeitschriftenartikel
K. Zdrodowski, A. Bekiesza, K. Radomski, I. Veretennicoff, T. Nasilowski, H. Thienpont, S. Kufner, F. Berghmans, Y. Carnicer, M. Decreton, Maria Kufner
A Cascadable Polarization-Based 1 to 9 Multimode Optical Fiber Switch using a PMMA Fiber Array Holder
IEEE Journal of Lightwave Technology, vol. 16, no. 8, pp. 1464-1472
1998
DOI: 10.1109/50.704612
Abstract anzeigen
We have constructed an optical fiber switch, which allows to route an information carrying laser beam to nine multimode optical fibers. The fibers are accurately positioned in a polymethylmethacrylate (PMMA) fiber array holder, fabricated with deep proton lithography. To switch light from one fiber to another, we use active control of the polarization of light by means of nematic liquid crystal retarders or ferroelectric polarization rotators. The system shows insertion losses as low as 3 dB and crosstalk ratios below -30 dB. These figures are still susceptible to considerable improvements. The switching speed is on the order of 10 Hz using nematic liquid crystals and was extended to 10 kHz with ferroelectric liquid crystals. Potential applications of the fiber switch are discussed. As an illustration we have demonstrated the multiplexing of optical fiber proximity sensors. We also describe scale reduction and cascadability issues.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenTC Teisnach SensorikBuch (Monographie)
S. Kufner, Maria Kufner
Micro-optics and lithography
1997
ISBN: 978-9054871675
Abstract anzeigen
"This book is a thorough review of current techniques for the fabrication of micro-optical elements. It gives an overview of diffractive and refractive micro-optics and includes also guided wave micro-optics. Special attention is given to new techniques including deep etch lithography, like excimer lasers, LIGA and high energy ion irradiation." "The book is of interest for all scientists in both industry and academia who are working in the field of compact micro-optical systems. This includes optical data transmission in waveguides and free-space, compact optical imaging systems and many other areas of optical engineering." "Graduate students will also find it a very useful introduction to this large and rapidly expanding field. It covers major techniques and describes methods for each, providing much 'how-to-do' information."--BOOK JACKET.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenTC Teisnach SensorikZeitschriftenartikel
S. Kufner, P. Chavel, Maria Kufner, M. Frank
Monolithic integration of microlens arrays and fiber holder arrays in PMMA with fiber selfcentering
Optics Letters, vol. 20, no. 3, pp. 276-278
1995
DOI: 10.1364/OL.20.000276
Abstract anzeigen
For many fiber applications the precise spacing from one fiber to another and the collimation of the outgoing light are important subjects. In the case of three-dimensional arrangements, such as fiber arrays, the complexity increases. The method of proton irradiation of poly(methyl methacrylate) permits the fabrication of slightly fan-shaped fiber holder arrays that can correct inhomogeneities of the fiber diameters in the micrometer range. Even a three-dimensional monolithic integration of fiber holders and corresponding microlenses can be achieved.
Version: 2.1.0