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Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (5)
- 8.0 Abteilungsleitung und andere (3)
- 8.1 Sensorik, mess- und prüftechnische Verfahren (2)
- 8.4 Akustische und elektromagnetische Verfahren (2)
- 8.5 Röntgenbildgebung (2)
- 9 Komponentensicherheit (2)
- 4 Material und Umwelt (1)
- 4.2 Material-Mikrobiom Wechselwirkungen (1)
- 5 Werkstofftechnik (1)
- 5.1 Mikrostruktur Design und Degradation (1)
Eingeladener Vortrag
- nein (23)
VDI/VDE-Guideline 5570 - The First Comprehensive Standard on Characterization and Testing of POF
(2002)
VDE-VDI-Richtlinie 5570
(2003)
Rückführung im Prüfwesen
(2003)
Ergebnisunsicherheit im Prüfwesen- Eine Einführung in Systematik und praktische Vorgehensweisen
(2005)
Ergebnisunsicherheit im Prüfwesen - eine Einführung in Systematik und praktische Vorgehensweisen
(2005)
Die ständige Überwachung von Bauwerken gewinnt zunehmend an Bedeutung. Mit Blick auf die Nachhaltigkeit ist die Verlängerung der Nutzungsdauer bestehender baulicher Konstruktionen von unschätzbarem Wert, sowohl aus finanziellen Gründen als auch unter Denkmalaspekten. Eine neue Methode zur Detektion von Strukturschädigungen basiert auf einer integrierten Auswertung von Messwerten verschiedener Sensoren nach der Methode der kleinsten Quadrate sowie der Interpretation der dabei auftretenden Langrange-Multiplikatoren. Diese Methode der Schädigungsanalyse wird anhand eines numerischen Beispiels aus einem Vier-Punkt-Biegeversuch mit einem Verbundträger näher erläutert. ---------------------------------------------------------------------------------------------------------
Structural health monitoring of structures is gaining increasingly importance. With regard to sustainability it is of great value for both financial reasons (to extend the useful life of existing architectural structures) and the aspects of listed buildings. A new method for the detection of structural damage is based on an integrated analysis of measurements of different sensors according to the method of least squares and the interpretation of the occurring Lagrange Multipliers. This method of damage analysis is illustrated by a numerical example of a four-point bending test with a composite beam.
Strukturintegrierte Sensorik
(2012)
Structural health monitoring by distributed fiber optic sensors embedded into technical textiles
(2012)
Technical textiles with embedded distributed fiber optic sensors have been developed for the purposes of structural health monitoring in geotechnical and civil engineering. The distributed fiber optic sensors are based on Brillouin scattering in silica optical fibers and OTDR in polymer optical fibers. Such 'smart' technical textiles are used for reinforcement of geotechnical and masonry structures. The embedded fiber optic sensors provide online information about the condition of the structure and about the occurrence and location of any damage or degradation.--------------------------------------------------------------------------------------------------------------------------------------------------------
Technische Textilien mit integrierten faseroptischen Sensoren eröffnen neue Möglichkeiten der Zustandsüberwachung (structural health monitoring) in Geotechnik und Ingenieurbau. Die verteilt messenden Sensoren basieren auf der Brillouin-Streuung in Glasfasern und auf der OTDR in polymeroptischen Fasern. Derartige 'intelligente' technische Textilien werden in erster Line zur Verstärkung von geotechnischen Bauwerken und von Gebäuden genutzt. Die integrierten Sensoren liefern eine zeitnahe Information über den bestimmungsgemäßen Zustand des Bauwerks sowie über die Entstehung und den Ort von lokalen Bauwerksschäden.
Messtechnik und Sensorik
(2011)
Langzeit-Monitoring an den Spannbetonbrücken des neuen Hauptbahnhofs Berlin (Lehrter Bahnhof)
(2008)
Spannbetonbrücken des neuen Hauptbahnhofs in Berlin, die etwa 170 m lang sind und auf 12 Stützen ruhen, werden für viele Jahre mit einem Monitorsystem überwacht. Gemessen werden langzeitig auftretende Setzungen und Hebungen an den Auflagerpunkten. Für die Messungen wird ein hydrostatisches und ein laseroptisches System für die vertikalen Verformungen eingesetzt, daneben Neigungsmesser und Dehnungsaufnehmer (elektrische und faseroptische) sowie Temperatur-Sensoren. Für die Auswertung wird eine neuartige Symbiose von experimenteller und mechanisch-numerischer Analyse angewendet.
Meßtechnik und Sensorik
(2007)
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.
The Split Hopkinson Pressure Bar (SHPB) or
Kolsky Bar is known as a method for analysing
mechanical properties of a material under dynamic
load. Referring to the name it is a splitted
Hopkinson Pressure Bar. The Hopkinson Bar is
related to its inventor Bertram Hopkinson (1914).
He used it to analyze stone samples under dynamic
load. Later his construction was improved by
Davies (1948) [1] and Kolsky (1949) [2], who had
the idea to split the bar and put a sample in
between.
The technique is used to measure a lot of
different mechanical properties of a material e.g.
the dynamic Youngs modulus, deformation
behaviour or to chart the dynamic stress-strain
diagram. Further applications are the measurement
of the elastic wave and the analysis of the
propagation of the wave [2]. In the last years there
was still an interest in measuring dynamic
properties with a SHPB. Nevertheless no
comprehensive validation of the system exists.
Another problem is that the stress and the strain in
the sample are only calculated with simplified
estimations.
The aim of this paper is to give a first
impression of important points validating the
system. On account of different setups of the
SHPB a validation of the used system is necessary.
Hence it is important to look at the theory. Further
in this paper the measurement results will be
shown in a strain over time diagram.
Die ständige Überwachung von Konstruktionen während ihrer Lebenszeit ist eine bedeutsame Aufgabe, die Gegenstand vielzähliger Forschungsaktivitäten ist. Unter dem Aspekt der Nachhaltigkeit ist die Verlängerung der Nutzungsdauer bestehender Konstruktionen von unschätzbarem Wert, sowohl aus finanziellen Gründen als auch unter dem Gesichtspunkt der Erhaltung der gebauten Umwelt und des Denkmalschutzes.Bei allen Erfolgen der Projekte zur Bauwerkserhaltung ist die Frage, wie entstehende Schädigungen rechtzeitig erkannt werden können, auch wenn sie erst geringfügig sind, nicht befriedigend beantwortet worden. In diesem Beitrag wird eine neue Methode zur Detektierung von Strukturschädigungenvorgestellt. Diese beruht auf einer integrierten Auswertung von Messwerten verschiedener Sensoren nach der Methode der kleinsten Quadrate sowie der Interpretation der dabei auftretenden Langrange-Multiplikatoren.Diese Methode der Schädigungsanalyse wird anhand eines numerischen Beispiels aus einemVier-Punkt-Biegeversuchmit einem Verbundträgernäher erläutert.
Fibre Optic Sensing
(2013)
Embedded sensors
(2013)
This chapter introduces and describes the concept of structural health monitoring (SHM) to engineers and designers of technical structures, and to the owners/operators of such structures. It formulates general principles for integrating and implementing measurement and signal processing technologies in the context of SHM to diagnose the condition, performance and health of a technical structure. Information and recommended methods for designing instrumentation, data acquisition, data processing and data analysis for any SHM application are offered.
This chapter summarizes the state of the art and current developments of guidelines for structural health monitoring (SHM) and performance control. Technical guidelines and standards for condition monitoring and technical diagnostics of rotary machines and for non-destructive testing are not reviewed in this chapter.
Fiber optic sensors have gained increasing importance in recent years and are well established in many areas of industrial applications. In this paper, we introduce a concept of a self-diagnostic fiber optic sensor. The presented sensor is to resolve the problems of embedded fiber optic sensors in complex structures and to enable the validation under operational conditions. For this purpose, different magnetostrictive coated fiber optic sensors were developed and various experiments were performed to verify their mode of Operation and to determine the respective reproducibility. The measuring principle is illustrated by obtained experimental results, which showed a change in wavelength from 1 pm at a magnetic field strength change of 0.25 mT.
In addition, the temperature characteristics of the implemented magnetostrictive sensor were analyzed and an experimental factor of 1.5 compared to a reference fiber optic sensor was determined.
Measurement and data recording systems are important parts of a holistic Structural Health Monitoring (SHM) system.
New sensor technologies such as fiber-optic sensors are often used; however, standards (or at least guidelines) are not yet available or internationally approved. This lack in standardization makes the acceptance of FOS technologies in complex SHM systems substantially difficult. A standard family for different FOS technologies is therefore being developed that should help to design SHM systems in an optimal way. International standardization activities take place in several standardization bodies such as IEC and ASTM, and within SHM societies such as ISHMII.
The paper reports on activities in standardization of fiber-optic sensors, on results already achieved, and on newly started projects. Combined activities of fiber sensor experts and SHM experts from Civil Engineering are presented. These contributions should help owners of structures as well as developers of sensors and monitoring systems to select effective and validated sensing technologies. Using these standards, both parties find recommendations how to proceed in development of SHM systems to evaluate the structural behavior based on e.g. standardized fiber optic sensors, and to derive necessary measures, e.g. the optimal maintenance strategy.
Karriere in der Forschung
(2014)
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.
The Split Hopkinson Pressure Bar (SHPB) is a materials testing apparatus primarily designed for the analysis of viscoplastic material behavior at very high strain rates.
Because of its complexity it is common practice to simplify the underlying exact mechanical theory by making strong assumptions. On the one hand this has to be done to achieve any results at all on the other hand one commits systematic errors. Therefore we utilize different numerical and Simulation methods to analyze and minimize these errors.
The absolute detection of a gap distance of loose and ftxed extrinsic Fabry-Perot interferometer (EFPI) sensors with conventional measurement Systems is not possible. Due to this EFPI-sensors were deemed to be unfit for distance determination in comparision with FBG sensors. With the conventional measurement method a continous measurement of the EFPIsensors was necessary. Otherwise data about the distance change was lost. Additional it is necessary to detect the tumaround points in the interference signal with 100%. This made it worse for the analysis and the use of the sensor. At BAM Federal Institute for Materials Research and Testing a measurement System called “EFPI-Scan” is developed which can measure the absolute gap distance of four connected EFPI-sensors synchronous. Every measurement channel is temperature independetn and long term stable. Test measurements showed a deviation of maximum ±1 gm per hour. Furthermore it is possible to measure with different measurement modes (abolute, relative and a combination of both). Special emphasis should be placed to the absolute measurement accuracy of ± 5 pm at a gap distance determination ftom 40 up to 4000 pm.
The Split Hopkinson Pressure Bar (SHPB) is a method for material characterization which works at strain rates from 102 - 104 1/s. This method can be used for example in the field of military engineering, in the field of deformation technology, automobile indurstry, aerospace industry or in other industrial fields. Controlled tests with the SHPB device enable Information about the dynamic material deformaion behaviour in the named strain rate area. The setup of the SHPB is not standarized and the measurement principle is dependent on simplifications. Due to this amongst others the problem with the dispersion of the measurement signal occurs. Furthermore it is possible that measurement uncertainties appear caused by the misalignment of the SHPB setup. In this work the influence of the alignment and a dispersion correction by pulse shaping is presented. On the one side for the alignment calibration tests are done. And on the other side for the dispersion influence correction with pulse shaping tests are done with TiA16V4. This material was choosen due to the fact that it can be compared with existing literature data.
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.