TY - CONF A1 - Habel, Wolfgang A1 - Schukar, Vivien A1 - Mewis, Franziska A1 - Kohlhoff, Harald ED - Yang, M. ED - Wang, D. ED - Rao, Y. T1 - Experimental validation of applied strain sensors - importance, methods and still unsolved challenges N2 - Fiber-optic strain sensors are increasingly used in very different technical fields. Sensors are provided with specifications defined by the manufacturer or ascertained by the interested user. If deformation sensors are to be used to evaluate the long-term behavior of safety-relevant structures or to monitor critical structure components, their performance and signal stability must be of high quality to enable reliable data recording. The measurement system must therefore be validated according to established technical rules and standards before its application and after. In some cases, not all details of the complex characteristic and performance of applied fiber-optic sensors are sufficiently understood, or can be validated because of a lack of knowledge and methods to check the sensors' behavior. This contribution focusses therefore on the importance of serious validation in avoiding a decrease or even deterioration of the sensors' function. Methods for validation of applied sensors are discussed and should reveal weaknesses in validation of embedded or integrated fiber-optic deformation and/or strain sensors. An outlook to some research work that has to be carried out to ensure a well-accepted practical use of fiber-optic sensors is given. T2 - 4th Asia Pacific optional sensors conference CY - Wuhan, China DA - 2013-10-15 KW - Fiber-optic sensor KW - Strain sensor KW - Reliability KW - Durability KW - Sensor characteristics KW - Application-related changes KW - Adhesive stability KW - Validation PY - 2013 U6 - https://doi.org/10.1117/12.2036591 SN - 0277-786X N1 - Serientitel: Proceedings of SPIE – Series title: Proceedings of SPIE VL - 8924 SP - 892410-1 - 892410-6 AN - OPUS4-29908 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Habel, Wolfgang A1 - Schukar, Vivien A1 - Steinke, F. A1 - Basedau, Frank ED - Ilki, A. ED - Motavalli, M. ED - Goksu, C. ED - Havranek, B. T1 - Investigation of the fiber-optic strain sensors' beahvior under offshore conditions to create standards for reliable application T2 - SMAR 2013 - 2nd Conference on smart monitoring, assessment and rehabilitation of civil structures CY - Istanbul, Turkey DA - 2013-09-09 KW - Fibre-optic sensor KW - Strain sensor KW - Reliability KW - Durability KW - Sensor characteristics KW - Offshore application KW - Harsh impacts PY - 2013 SN - 978-3-033-04055-7 SP - 1 EP - 8(?) CY - Istanbul, Turkey AN - OPUS4-29909 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Habel, Wolfgang A1 - Schukar, Vivien A1 - Kusche, Nadine ED - Peters, K.J. ED - Ecke, W. ED - Matikas, T.E. T1 - The role of experimental validation in achieving reliable measurement data with applied FBG strain sensors N2 - Fiber-optic strain sensors are increasingly used in very different technical fields. Sensors are provided with specifications defined by the manufacturer or ascertained by the interested user. In some cases, sensor specification is not sufficiently validated and must therefore additionally be validated in a laboratory, primarily to ensure reliable measurement information over the intended period of operation. Even if the performance of delivered sensor is well specified, the sensor's strain characteristics and the performance of an applied sensor can significantly differ from the virgin sensor's performance. In this case, applied sensors do not provide full reliability and lead sometimes to uncertain measurement results. This contribution will therefore focus on the role of validation in avoiding a decrease or even deterioration of the sensor function of applied sensors. Experimental validation - not only modelling - is very important, however, before experimental investigations are planned knowledge about key issues and problems that influence the measurement results must be available. Few aspects to be considered and investigated will be discussed. Selected experimental facilities to reveal weaknesses in the sensor function will be described; an outlook to open questions is given. T2 - Smart sensor phenomena, technology, networks, and systems integration 2013 CY - San Diego, CA, USA DA - 2013-03-10 KW - Fibre-optic sensor KW - Strain sensor KW - Reliability KW - Durability KW - Sensor characteristics KW - Application-related changes KW - Adhesive stability KW - Validation PY - 2013 U6 - https://doi.org/10.1117/12.2009677 SN - 0277-786X N1 - Serientitel: Proceedings of SPIE – Series title: Proceedings of SPIE VL - 8693 IS - Paper 12 SP - 86930C-1 - 86930C-11 AN - OPUS4-29911 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Habel, Wolfgang A1 - Schukar, Vivien A1 - Kusche, Nadine T1 - Calibration facility for quality certification of surface-attached fiber optic and electrical strain sensors N2 - Strain measurement in structures witli the purpose of long-term structurai health inonitoring must provide reliable inforination about the structure’s behavior over the whole period of use. The user must be sure that installed sensors are validated and work to the utmost satisfactiou. For this purpose, sensor Systems are tested using special facilities. Bccause it is not easy to characterize the strain transfer quality from the host structure into surface-applied strain sensors, a unique testing facility has been developed. Originally developed for fiber Bragg grating based sensors, the KALFOS facility (= calibration of fiber optic sensors) can also be used for electrical strain sensors. Calibration ineasurements are referenced by unbinsed Digital Image Correlation (D1C) and Electronic Speckle Pattern Interferometer (ESPI) methods. The strain transfer behavior can experimentally be analyzed and investigated under combined thermal and mechanical loading conditions and allows revealing wealuiesses in couimonly used attachment methodologies. The deformation of all members (particularly the coating/substrate - adhesive combination) in the sensing area is physically independently gained and recorded. Results achievcd allow precise description of the strain transfer function, Validation of the longterm strain sensor characteristics, matching of specific measurement requirements with environmental conditions, and, moreover, the verification of Standards for use of strain sensors. T2 - IEEE Sensors 2011 conference CY - Limerick, Ireland DA - 28.10.2011 KW - Fibre optic sensors KW - Structural health monitoring KW - Validation KW - Strain sensor KW - Surface application reliability PY - 2011 SN - 978-1-4244-9288-6 U6 - https://doi.org/10.1109/ICSENS.2011.6127253 SP - 1337 EP - 1340 AN - OPUS4-24655 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Habel, Wolfgang A1 - Schukar, Vivien A1 - Tkachenko, Viktoriya T1 - How do application-related issues influence the reliability of fiber optic strain measurements? N2 - Fibre optic strain sensors are increasingly used and sensor systems are provided with specifications. Even if the performance is well specified, the strain characteristics of the sensor, strain transfer factor, mechanical stability under thermal influences, the performance of applied strain sensors can seriously differ from virgin sensor's the performance. The contribution will focus on issues that can deteriorate the sensor function or reduce the reliability of measurement results. Aspects are considered how to come to reliable strain measurements and how to validate strain measurements of applied sensors. Related to this topic, European activities like the recently started European COST TD1001 action, called (OfSeSa) will be presented. T2 - IEEE Sensors 2011 conference CY - Limerick, Ireland DA - 28.11.2011 KW - Fibre optic sensors KW - Structural health monitoring KW - Validation KW - Strain sensor KW - Surface application reliability PY - 2011 SN - 978-1-4244-9288-6 SP - 947 EP - 950 AN - OPUS4-24656 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Habel, Wolfgang A1 - Kusche, Nadine A1 - Münzenberger, Sven A1 - Schukar, Vivien T1 - KALFOS - a validation facility for strain transfer characterization of surface-applied strain sensors N2 - Strain sensors embedded in or attached to structural components have to measure the real deformation of the structure over the whole period of use. The user must know how reliably installed sensors provide strain measurement results. For this purpose, test facilities or coupon tests are used. In order to characterize the strain transfer quality from the host structure into surface-applied strain sensors, a unique testing facility has been developed. This facility can be used both for fiber optic and resistance strain sensors. Originally developed for fiber Bragg grating based sensors, the KALFOS facility (=calibration of fiber optic sensors) uses Digital Image Correlation (DIC) and Electronic Speckle Pattern Interferometer (ESPI) as unbiased referencing methods. It is possible to determine experimentally the strain transfer mechanism under combined thermal and mechanical loading conditions. This experimental characterization method will reveal weaknesses in commonly used strain sensors, and the investigation of the material systems used for fiber optic and other strain sensors (particularly the coating/substrate - adhesive combination). The KALFOS facility allows matching of specific measurement requirements with environmental conditions. T2 - SAE 2011 AeroTech Congress & Exhibition CY - Toulouse, France DA - 18.10.2011 KW - Fiber optic sensors KW - Structural health monitoring KW - Validation KW - Strain sensor KW - Surface application PY - 2011 U6 - https://doi.org/10.4271/2011-01-2606 IS - Paper 2011-01-2606 SP - 1 EP - 7 AN - OPUS4-24643 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Habel, Wolfgang A1 - Schukar, Vivien ED - Ecke, W. ED - Peters, K.J. ED - Matikas, T.E. T1 - FOS standards and testing methods to validate fibre optic strain measurements N2 - Fiber optic sensors are increasingly used because of their outstanding performance or if special requirements avoid the application of conventional electrical sensors. The scientific background for optical fiber sensors is well developed; however, the characteristic of sensors applied in rather harsh environment are almost always different from characteristics determined in laboratory or before its installation. In order to achieve long-term stable function and reliable measurement data after application and under harsh environmental conditions, guidelines for characterization and specification of sensor components are needed as well as methodologies for testing the sensor performance must be developed. Performance tests carried out revealed that there are still some restrictions with respect to long-term reliable use: first, some sensor products available on the market are not very often appropriately characterized, described and validated; second, application procedures are not always defined due to a lack of understanding the micromechanical issues in the interface zone between sensor and measuring object. Application procedures and profound knowledge of materials behaviour are necessary to get results from the sensor that can be reliably used. The paper describes first guidelines to prove the quality of fiber optic strain sensors, a testing facility developed for unbiased tests and certification of surface-applied sensors as well as result from comparison of commercially available strain sensors. T2 - SPIE-Conference 'Smart sensor phenomena, technology, networks, and systems 2011' CY - San Diego, CA, USA DA - 06.03.2011 KW - Fiber optics KW - Strain sensor KW - Reliability KW - Durability KW - Creep KW - Application KW - Adhesive KW - Standards KW - Guideline KW - Testing PY - 2011 SN - 978-0-8194-8547-2 U6 - https://doi.org/10.1117/12.881238 VL - 7982 SP - 79820O-1 EP - 79820O-12 AN - OPUS4-24271 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -