TY - JOUR A1 - Clauß, F. A1 - Epple, Niklas A1 - Ahrens, M. A. A1 - Niederleithinger, Ernst A1 - Mark, P. T1 - Comparison of Experimentally Determined Two-Dimensional Strain Fields and Mapped Ultrasonic Data Processed by Coda Wave Interferometry JF - Sensors N2 - Due to the high sensitivity of coda waves to the smallest structural alterations such as strain, humidity or temperature changes, ultrasonic waves are a valid means to examine entire structures employing networks of ultrasonic transducers. In order to substantiate this ex ante assessment, the viability of measuring ultrasonic waves as a valid point of reference and inference for structural changes is to be further scrutinized in this work. In order to investigate the influence of mechanical strain on ultrasonic signals, a four-point bending test was carried out on a reinforced concrete beam at Ruhr University Bochum. Thus, measurements collected from a network of selected transducer pairings arranged across the central, shear-free segment of the test specimen, were correlated to their respective strain fields. Detected ultrasonic signals were evaluated employing Coda Wave Interferometry. Such analysis comprised the initial non-cracked state as well as later stages with incremental crack depth and quantity. It was to ascertain that the test specimen can in fact be qualitatively compartmentalized into areas of compression and tension identified via Relative Velocity Changes presented in Attribute Maps. However, since results did not entail a zero crossing, i.e., neither positive nor negative values were to be calculated, only relative changes in this work displayed staggered over the height of the object under test, are discussed. Under the given methodological premises, additional information is currently required to make quantitative assertions regarding this correlation of ultrasonic and strain results. This holds true for the comparability of the ultrasonic and strain results for both non-cracked and even the cracked state. KW - Digital image correlation KW - Fiber optic sensors KW - Coda Wave Interferometry KW - Ultrasound KW - Concrete PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-510501 DO - https://doi.org/10.3390/s20144023 SN - 1424-8220 VL - 20 IS - 14 SP - Paper 4023, 1 PB - MDPI CY - Basel AN - OPUS4-51050 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Habel, Wolfgang A1 - Brunner, F.K. T1 - Faseroptische Sensoren für den Einsatz im Monitoring: Ein Überblick JF - Allgemeine Vermessungs-Nachrichten : AVN N2 - Die herausragenden Eigenschaften faseroptischer Sensoren beim Monitoring geotechnischer Strukturen werden diskutiert und ihre Vor- und Nachteile zusammengefasst. Es werden die Grundlagen der wichtigsten faseroptischen Sensoren (Rückstreu-, Faser-Bragg-Gitter-, Fabry-Perot-Sensoren, Mach-Zehnder-Interferometer sowie Sensoren auf Basis der Niedrig-Kohärenz-Interferometrie) aufbereitet. KW - Monitoring KW - Faseroptische Sensoren KW - Faser-Bragg-Gitter KW - Interferometrische Sensoren KW - Fiber optic sensors KW - Fiber Bragg grating KW - Interferometric sensors PY - 2011 SN - 0002-5968 VL - 6 SP - 204 EP - 211 PB - Wichmann CY - Heidelberg AN - OPUS4-23911 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hicke, Konstantin A1 - Eisermann, René A1 - Chruscicki, Sebastian T1 - Enhanced Distributed Fiber Optic Vibration Sensing and Simultaneous Temperature Gradient Sensing Using Traditional C-OTDR and Structured Fiber with Scattering Dots JF - Sensors N2 - We present results demonstrating several beneficial effects on distributed fiber optic vibration sensing (DVS) functionality and performance resulting from utilizing standard single mode optical fiber (SMF) with femtosecond laser-inscribed equally-spaced simple scattering dots. This modification is particularly useful when using traditional single-wavelength amplitude-based coherent optical time domain reflectometry (C-OTDR) as sensing method. Local sensitivity is increased in quasi-distributed interferometric sensing zones which are formed by the fiber segments between subsequent pairs of the scattering dots. The otherwise nonlinear transfer function is overwritten with that of an ordinary two-beam interferometer. This linearizes the phase response to monotonous temperature variations. Furthermore, sensitivity fading is mitigated and the demodulation of low-frequency signals is enabled. The modification also allows for the quantitative determination of local temperature gradients directly from the C-OTDR intensity traces. The dots’ reflectivities and thus the induced attenuation can be tuned via the inscription process parameters. Our approach is a simple, robust and cost-effective way to gain these sensing improvements without the need for more sophisticated interrogator technology or more complex fiber structuring, e.g., based on ultra-weak FBG arrays. Our claims are substantiated by experimental evidence. KW - Fiber optic sensors KW - Distributed vibration sensing KW - DVS KW - Distributed temperature gradient sensing KW - DTGS KW - C-OTDR KW - Phase-sensitive KW - OTDR KW - Fiber structuring KW - Fs-inscription PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-499281 DO - https://doi.org/10.3390/s19194114 VL - 19 IS - 19 SP - 4114 PB - MDPI CY - Basel, Switzerland AN - OPUS4-49928 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schukar, Marcus A1 - Krebber, Katerina A1 - Scheer, M. T1 - Strahlungsüberwachung mit Faser-Bragg-Gitter-Sensoren am Elektronenspeicherring BESSY II JF - Technisches Messen N2 - Die Eignung von Faser-Bragg-Gitter-(FBG)-Sensoren zur Messung ionisierender Strahlung wurde an einem Undulator des Elektronenspeicherrings BESSY II untersucht. Über einen Zeitraum von 20 Wochen wurde eine durch Strahlung verursachte Bragg-Wellenlängenänderung der FBG-Sensoren von 25pm gemessen, was einer Strahlendosis von 720 Gy entspricht. The suitability of using fiber Bragg grating (FBG) sensors for the measurement of ionizing radiation on the electron storage ring BESSY II by measuring the Bragg wavelength shift caused by radiation was investigated. During a time period of 20 weeks a Bragg wavelength shift of 25pm caused by the ionizing radiation was measured by FBG sensors at the storage ring. This Bragg wavelength shift corresponds to a radiation dose value of 720 Gy. KW - Faseroptische Sensoren KW - Faser-Bragg-Gitter KW - Dosimetrie KW - Strahlungssensoren KW - Elektronenspeicherring KW - Fiber optic sensors KW - Fiber Bragg gratings KW - Radiation dosimetry KW - Radiation sensors KW - Electron storage ring PY - 2008 DO - https://doi.org/10.1524/teme.2008.0834 SN - 0340-837X SN - 0178-2312 SN - 0171-8096 VL - 75 IS - 4 SP - 245 EP - 250 PB - Oldenbourg CY - München AN - OPUS4-17655 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -