TY - JOUR A1 - Appajaiah, Anilkumar A1 - Wachtendorf, Volker A1 - Daum, Werner T1 - Characterization of thermo-oxidative stability of polymer optical fibers using chemiluminescence technique JF - Polymer degradation and stability N2 - The thermo-oxidative stability of commercially available polymer optical fibers (POFs) and their components (cores and claddings) was investigated. All the bare POFs (core and cladding only) studied here were based on poly(methyl methacrylate) (PMMA) core. The fibers were exposed to 100 °C/low humidity for about 4200 h. Chemiluminescence (CL) technique was applied to investigate the thermo-oxidative stability and for measuring the transmission loss during exposure a prototype device called multiplexer was used. POFs exhibited variation in thermo-oxidative stability although they possessed identical core material PMMA. This was due to difference in the chemical compositions of claddings. Claddings were more susceptible to the thermo-oxidative degradation compared to cores. The thermo-oxidative degradation of both the cladding and the core was found in POFs as a result of climatic exposure. POFs showed an early drop-off followed by a slow decline of transmission. The early drop-off of transmission was attributed to physical changes like thermal expansion and the slow decline of transmission to chemical changes like oxidative degradation of POFs. A good linear relationship between optical transmission stability and thermo-oxidative stability of POFs was established from these studies. KW - Polymer optical fibers (POFs) KW - Chemiluminescence (CL) KW - Thermo-oxidative stability KW - Aging KW - Optical transmission stability PY - 2006 DO - https://doi.org/10.1016/j.polymdegradstab.2006.05.006 SN - 0141-3910 SN - 1873-2321 VL - 91 IS - 11 SP - 2605 EP - 2613 PB - Applied Science Publ. CY - London AN - OPUS4-13984 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Appajaiah, Anilkumar A1 - Wachtendorf, Volker A1 - Daum, Werner T1 - Climatic exposure of polymer optical fibers: Thermooxidative stability characterization by chemiluminescence JF - Journal of applied polymer science N2 - The optical transmission stability was investigated for commercially available polymer optical fibers (POFs) which were exposed to a climate of 92°C and 95% relative humidity for about 3300 h. The optical transmission stability of POFs was correlated to their thermooxidative stability. POFs possessed identical core material, poly(methyl methacrylate), but they differed in the materials used for the claddings. The optical transmission was measured online using a prototype device called multiplexer. The chemiluminescence (CL) technique was applied to characterize the thermooxidative stability and degradation of POFs. CL analysis reveals the thermooxidative degradation of bare POFs (core and cladding), predominantly of the claddings, as a result of climatic exposure. Ultraviolet-visible transmittance measurements demonstrated more changes in the claddings as compared to the cores due to degradation. The CL and optical measurements data indicated that the optical transmission stability of POFs was dependent mainly on the thermooxidative stability of the claddings and their chemical compositions. KW - Ageing KW - Polymer optical fiber KW - Degradation KW - Chemiluminescence KW - Transparency PY - 2007 DO - https://doi.org/10.1002/app.23955 SN - 0021-8995 SN - 1097-4628 VL - 103 IS - 3 SP - 1593 EP - 1601 PB - Wiley InterScience CY - Hoboken, NJ AN - OPUS4-19072 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bartholmai, Matthias A1 - Neumann, Patrick P. A1 - Kohlhoff, Harald A1 - Daum, Werner T1 - Multi-sensor systems for safety-related monitoring T2 - Sensor 2013 - 16th International conference on sensors and measurement technology (Proceedings) T2 - Sensor 2013 - 16th International conference on sensors and measurement technology CY - Nürnberg, Germany DA - 2013-05-14 KW - Multi-sensor system KW - Condition monitoring KW - Safety management KW - Hazardous scenarios KW - Data-fusion PY - 2013 SN - 978-3-9813484-3-9 DO - https://doi.org/10.5162/sensor2013/B5.2 N1 - Serientitel: AMA Conferences – Series title: AMA Conferences SP - 268 EP - 272 AN - OPUS4-28518 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bartholmai, Matthias A1 - Werner, Klaus-Dieter A1 - Johann, Sergej A1 - Daum, Werner ED - Cosmi, F. T1 - Characterization of the temperature behavior of a piezoresistive accelerometer T2 - 34rd Danubia - Adria Symposium on Advances in Experimental Mechanics - Book of proceedings N2 - Piezoresistive accelerometers use a strain-sensing element, generally made of semiconductor material, e.g., silicon to convert the mechanical motion into an electrical signal. This element is usually designed in form of a cantilever beam loaded with a mass. Acceleration causes bending of the beam, which produces a change of electrical resistance proportional to the applied acceleration. Main advantages of piezoresistive accelerometers in comparison to other types, e.g., piezoelectric and capacitive, is their robust and highly dynamic behavior, which qualifies them for application in high impact shock applications. Mechanical damping is typically implemented with silicon oil in a way that the output signal is undistorted over a wide frequency range. These characteristics principally qualify them for the application in drop tests carried out at BAM, for which they are calibrated over the frequency range from 1 to 4 kHz. However, using silicon oil for damping, has the drawback of temperature dependent change of its viscosity, leading to temperature dependent deviation of the accelerometer’s sensitivity. This study presents experimental results of the temperature behavior of a piezoresistive accelerometer with a dynamic range up to ±5000 g. This type of accelerometer is applied for drop tests which are partially performed at temperatures of -40 or +100 °C. T2 - 34th Danubia-Adria Symposium on Advances in Experimental Mechanics CY - Trieste, Italy DA - 19.09.2017 KW - Accelerometer KW - Temperature behavior KW - Drop test PY - 2017 UR - https://www.openstarts.units.it/handle/10077/14921 SN - 978-88-8303-863-1 SP - 93 EP - 95 CY - Trieste AN - OPUS4-42109 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bartholmai, Matthias A1 - Werner, Klaus-Dieter A1 - Kohlhoff, Harald A1 - Helmerich, Rosemarie A1 - Daum, Werner ED - Aulova, Alexandra ED - Rogelj Ritonja, A. ED - Emri, I. T1 - Long-Term measurement of vertical displacements at the outer concrete bridges of the Berlin Main Station T2 - 33rd Danubia- Adria Symposium on Advances in Experimental Mechanics - BOOK OF ABSTRACTS N2 - Berlin Main Station is the largest multi-level station in Europe. Its daily passenger number amounts to over 300.000. Structures built for such a large number of people require a high-level safety standard. The station was built on the inner city site of the historic Lehrter Bahnhof. The conditions for building and start of operation were challenging by several reasons. The typical sandy ground with a high level of groundwater makes the permanent static stability of such a complex structure difficult. Several completed, ongoing, and planned construction activities in the immediate vicinity of the station influence the ground settlement of the whole area. On basis of the structural design an impact prediction was calculated, which expected certain vertical displacements particularly between the single columns of the outer concrete bridges of the building. These columns support the glass roof construction, which only allows a defined limit of displacement. In order to avoid damage, a concept for monitoring and adjusting potentially occurring displacements was developed for installation at the outer bridges of the station. T2 - 33rd Danubia- Adria Symposium on Advances in Experimental Mechanics CY - Portorož, Slovenia DA - 20.09.2016 KW - Berlin Main Station KW - Differential displacements KW - Hydraulic levelling system KW - Laser-based displacement measuring system KW - Monitoring KW - Strain measurements PY - 2016 SN - 978-961-94081-0-0 SP - 166 EP - 167 CY - Ljubljana AN - OPUS4-37646 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Brandes, K. A1 - Daum, Werner A1 - Hofmann, Detlef A1 - Basedau, Frank A1 - Kubowitz, P. T1 - Innovative structural damage detection of bridges by least squares adjustment with constraints T2 - 32nd Danubia-Adria Symposium on advances in experimental mechanics (Proceedings) T2 - 32nd Danubia-Adria Symposium on advances in experimental mechanics CY - Starý Smokovec, Slovakia DA - 2015-09-22 PY - 2015 SN - 978-80-554-1094-4 SP - 18 EP - 19 CY - Zilina AN - OPUS4-34486 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brandes, K. A1 - Daum, Werner A1 - Hofmann, Detlef A1 - Basedau, Frank A1 - Kubowitz, P. T1 - Innovative structural damage detection of bridges by least squares adjustment with constraints JF - Materials Today: Proceedings N2 - Long-term monitoring of bridges requires the early detection of spreading damage because very often the damage is not really visible. For many decades engineers and scientists relayed on dynamic methods especially modal ones. However, after fundamental tests by the U.S. FHWA in 1993, it became evident that more successful methods should be developed, but no innovation really happened. A substantial innovative detection method started four years ago from Lagrange Multiplier Testing which eventually resulted in experimental verification based on measurement of deflection and curvature of the bridge beam and together the methodological combination of both. T2 - 32nd DANUBIA ADRIA SYMPOSIUM on Advances in Experimental Mechanics CY - Starý Smokovec – High Tatras, Slovakia DA - 22.09.2015 KW - Damage detection of bridges KW - Monitoring KW - Lagrange multiplier test PY - 2016 DO - https://doi.org/10.1016/j.matpr.2016.03.025 SN - 2214-7853 VL - 3 IS - 4 SP - 942 EP - 946 PB - Elsevier AN - OPUS4-36667 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Brandes, K. A1 - Daum, Werner A1 - Hofmann, Detlef A1 - Kubowitz, P. T1 - Lagrange multiplier test for structural damage of bridges T2 - 31st Danubia-Adria Symposium on advances in experimental mechanics (Proceedings) N2 - Detecting spreading damage in bridges is a demanding task for engineers today when the ageing infrastracture of industriaiized countries is degradating more and more. To successfully deal with tbis problem, a really advanced method has been elaborated basing on Langrange Multiplier (LM) tests and following the principle of simplicity by Hilbert and extending comments by Helmholtz refering to a combination of measurement and analytical treatment. Finally, an easy mathematical fonnation has been created. T2 - 31st Danubia-Adria Symposium on advances in experimental mechanics CY - Kempten, Germany DA - 24.09.2014 PY - 2014 SN - 978-3-00-046740-0 SP - 213 EP - 214 AN - OPUS4-31725 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Brandes, Klaus A1 - Daum, Werner A1 - Buchhardt, Frank T1 - Monitoring of Bridges by Advanced Methods of Experimental - Mechanical Symbiosis T2 - International Association for Bridge and Structural Engineering (IABSE) Symposium 2007, September 19-21, 2007, Weimar T2 - International Association for Bridge and Structural Engineering (IABSE) Symposium 2007 CY - Weimar, Deutschland DA - 2007-09-19 KW - Long-term monitoring KW - Sensors KW - Experimental-analytical symbiosis KW - Bridges KW - Lagrangian Multipliers KW - Structural modelling PY - 2007 SN - 978-3-85748-116-1 VL - 93 SP - 1 EP - 8 CY - Weimar AN - OPUS4-16327 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Brandes, Klaus A1 - Daum, Werner A1 - Buchhardt, Frank ED - Paulo J.S. Cruz, ED - Dan M. Frangopol, ED - Luis C. Neves, T1 - Long-term monitoring of concrete bridges by direct combination of experimental and mechanical analysis T2 - 3. International Conference on Bridge Maintenance, Safety and Management "Bridge Maintenance, Safety, Management, Life-Cycle Performance and Cost", July 16-19, 2006, Porto, Portugal (Proceedings) T2 - 3. International Conference on Bridge Maintenance, Safety and Management "Bridge Maintenance, Safety, Management, Life-Cycle Performance and Cost", IABMAS `06 CY - Porto, Portugal DA - 2006-07-16 PY - 2006 SN - 978-0-415-40315-3 SP - 1 EP - 8 PB - Taylor & Francis CY - Leiden, The Netherlands AN - OPUS4-16395 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -