TY - JOUR A1 - Schilder, Constanze A1 - Kusche, Nadine A1 - Schukar, Vivien A1 - Münzenberger, Sven A1 - Habel, Wolfgang T1 - Experimental qualification by extensive evaluation of fibre optic strain sensors JF - Measurement science and technology N2 - Fibre optic strain sensors used in practical applications have to provide reliable measurements. Therefore, the applied sensor and the sensor systems must be validated experimentally. This can be achieved with facilities which use physically independent measurement systems in order to avoid the influences caused by the application of a reference sensor. This paper describes the testing methods of the specially developed validation facility KALFOS for the qualification and evaluation of surface-applied strain sensors. For reliable sensor results, the performance of fibre optic strain patches with and without FBG under combined thermal and mechanical loading was investigated. Additionally, the strain gauge factor of the fibre optic strain patches with FBG was determined experimentally and compared to the specified strain gauge factor. These results will be the basis for the development of guidelines and standards concerning the application of the sensors. KW - Evaluation KW - Qualification KW - Strain transfer KW - Fibre optic sensors KW - Fibre Bragg grating KW - Patch KW - Strain gauge KW - Validation facility KW - Laser extensometer KW - Electronic speckle pattern interferometry PY - 2013 DO - https://doi.org/10.1088/0957-0233/24/9/094005 SN - 0957-0233 SN - 1361-6501 VL - 24 IS - 9 SP - 094005-1 EP - 094005-7 PB - IOP Publ. Ltd. CY - Bristol AN - OPUS4-29424 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Niederleithinger, Ernst A1 - Weller, Andreas A1 - Lewis, R. T1 - Evaluation of geophysical techniques for dike inspection JF - Journal of environmental & engineering geophysics N2 - After some river embankment failures during recent floods in Germany, major investigation and improvement programs for river embankments have been implemented. Presently, the investigation mainly relies on existing documentation, visual inspection, and drilling and sampling. Geophysical techniques, which are applied non-destructively from the surface, have the potential to cover the gaps between sampling points and to enhance the reliability of subsurface information. This paper describes the evaluation results for resistivity, electromagnetic, seismic and GPR techniques acquired at a test site along the Mulde River in eastern Germany. The work was carried out under the government funded project DEISTRUKT. Each geophysical method has its own specific advantages and limitations. Keeping the requirements posed by current German guidelines for river embankments in mind, 2–D electrical resistivity tomography (ERT) is the method of first choice. However, all geophysical results have to be calibrated carefully using information, such as material properties and depth of structures, determined from boreholes. Although some recommendations are provided here, a set of detailed recommendations have been compiled in a handbook. KW - Dikes KW - Embankments KW - Flood KW - Geophysics KW - Geotechnics KW - Evaluation PY - 2012 DO - https://doi.org/10.2113/JEEG17.4.185 SN - 1083-1363 VL - 17 IS - 4 SP - 185 EP - 195 PB - EEGS CY - Denver, Colo., USA AN - OPUS4-27490 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Osterloh, Kurt A1 - Bücherl, T. A1 - Lierse von Gostomski, C. A1 - Zscherpel, Uwe A1 - Ewert, Uwe A1 - Bock, S. T1 - Filtering algorithm for dotted interferences JF - Nuclear instruments and methods in physics research A N2 - An algorithm has been developed to remove reliably dotted interferences impairing the perceptibility of objects within a radiographic image. This particularly is a major challenge encountered with neutron radiographs collected at the NECTAR facility, Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II): the resulting images are dominated by features resembling a snow flurry. These artefacts are caused by scattered neutrons, gamma radiation, cosmic radiation, etc. all hitting the detector CCD directly in spite of a sophisticated shielding. This makes such images rather useless for further direct evaluations. One approach to resolve this problem of these random effects would be to collect a vast number of single images, to combine them appropriately and to process them with common image filtering procedures. However, it has been shown that, e.g. median filtering, depending on the kernel size in the plane and/or the number of single shots to be combined, is either insufficient or tends to blur sharp lined structures. This inevitably makes a visually controlled processing image by image unavoidable. Particularly in tomographic studies, it would be by far too tedious to treat each single projection by this way. Alternatively, it would be not only more comfortable but also in many cases the only reasonable approach to filter a stack of images in a batch procedure to get rid of the disturbing interferences. The algorithm presented here meets all these requirements. It reliably frees the images from the snowy pattern described above without the loss of fine structures and without a general blurring of the image. It consists of an iterative, within a batch procedure parameter free filtering algorithm aiming to eliminate the often complex interfering artefacts while leaving the original information untouched as far as possible. KW - Neutron KW - Radiography KW - Tomography KW - Filtering KW - Evaluation KW - NECTAR PY - 2011 DO - https://doi.org/10.1016/j.nima.2011.01.107 SN - 0168-9002 SN - 0167-5087 VL - 651 IS - 1 SP - 171 EP - 174 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-24917 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -