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Schlagworte
- Radar (39)
- Beton (37)
- Zerstörungsfreie Prüfung (26)
- Concrete (25)
- Zerstörungsfreie Prüfung im Bauwesen (24)
- Monitoring (23)
- Non-destructive testing (21)
- Bewitterung (18)
- Korrosion (16)
- Ultraschall (16)
Organisationseinheit der BAM
- 7 Bauwerkssicherheit (14)
- 6 Materialchemie (10)
- 6.1 Oberflächen- und Dünnschichtanalyse (10)
- 4 Material und Umwelt (7)
- 8 Zerstörungsfreie Prüfung (7)
- 7.4 Baustofftechnologie (5)
- 7.1 Baustoffe (4)
- 2 Prozess- und Anlagensicherheit (3)
- 3 Gefahrgutumschließungen; Energiespeicher (3)
- 4.5 Kunst- und Kulturgutanalyse (3)
The main obstacle to bottom ash (BA) being used as a recycling aggregate is the content of salts and potential toxic elements (PTEs), concentrated in a layer that coats BA particles. This work presents a dry treatment for the removal of salts and PTEs from BA particles. Two pilotscale abrasion units (with/without the removal of the fine particles) were fed with different BA samples. The performance of the abrasion tests was assessed through the analyses of particle size and moisture, and that of the column leaching tests at solid-to-liquid ratios between 0.3 and 4. The results were: the particle-size distribution of the treated materials was homogeneous (25 wt % had dimensions <6.3 mm) and their moisture halved, as well as the electrical conductivity of the leachates. A significant decrease was observed in the leachates of the treated BA for sulphates (44%),
chlorides (26%), and PTEs (53% Cr, 60% Cu and 8% Mo). The statistical analysis revealed good correlations between chloride and sulphate concentrations in the leachates with Ba, Cu, Mo, and Sr, illustrating the consistent behavior of the major and minor components of the layer surrounding BA particles. In conclusion, the tested process could be considered as promising for the improvement of BA valorization.
Identification of short transient signals within impact-echo data using the Hilbert-Huang-Transform
(2005)
Über den Kernstrahlungseinfluß auf elektrische Meßwertaufnehmer, insbesondere Dehnungsmeßstreifen
(1978)
Zur Feuchtemessung in Beton
(1978)
In this paper a new approach for quantitative non-destructive testing (NDT) of near-surface structures in civil engineering (CE) with active thermography is presented. It adopts the method known as pulsed phase thermography (PPT) for the special requirements of NDT-CE and was developed in a German research project of the Federal Institute for Materials Research and Testing (BAM) in cooperation with the Technical University of Berlin. The new quantitative concept that might be understood as a square pulse thermography in frequency domain or an amplitude-expanded PPT with square pulse heating is based on the thermal diffusivity of the material and the characteristic frequency of the negative maximum phase and amplitude contrast. It aims at complementing the established approaches for defects depth calculation for measurements with long heating and observation times quite usual at active thermography in CE but is easily extendable to other fields of application. After an introduction to the basics of active thermography in CE and the thermography concept of BAM, qualitative results of several case studies will be presented. The main focus of the last section of this contribution is on applications of the new quantitative approach at test specimens of BAM to determine the concrete cover of artificially manufactured defects.
Thermography (IR) allows global visualization of temperature distribution on surfaces with high accuracy. This potential can be used for visualization of fluid mechanics effects at the intersection of laminar and turbulent flows, where temperature jumps appear due to convection and friction i.e. for the optimization in the design of airplane geometries. In civil engineering too it is the aspiration of the modern engineer of light weight structures to meet singular loads like wind peaks rather by intelligent structures and materials than by massive structures. Therefore the "Institute of Conceptual and Structural Design" of the Technical University of Berlin (TUB) is working on the development of adaptive structures, optimized geometry and intelligent microstructures on surfaces of structural elements. The paper shows the potential of modern computational fluid dynamics (CFD) in combination with thermography (IR) to optimize structures by visualization of laminar-tumultuous border layer currents. Therefore CFD simulations and IR wind tunnel experiments will be presented and discussed. For simulations and experiments - artificial and structural elements of the cable-stayed Strelasund Bridge, Germany, are used.
Struktur- und Feuchteuntersuchungen von Bauteil- und Bauwerksoberflächen mit der Impuls-Thermografie
(2005)
Nach einer Einführung in die Puls-Phasen-Thermografie (PPT) wird ein neuer Ansatz für die Defekttiefenbestimmung im Frequenzraum mittels der sogenannten charakteristischen Frequenz des minimalen Phasen- und Amplitudenkontrastes zwischen Fehlstelle und ungestörtem Bereich entwickelt und anhand von systematischen Untersuchungen an Probekörpern der Bundesanstalt für Materialforschung und -prüfung und ergänzenden Simulationsrechnungen überprüft.
Die mit Rechteckimpuls-Spektral-Thermografie (RST) bezeichnete Methode, die auch als eine Rechteckimpuls-Thermografie (RIT) im Frequenzbereich oder eine durch Amplitudenauswertung ergänzte PPT für Rechteckimpulserwärmung verstanden werden kann, soll die existierenden Ansätze ergänzen und bietet eine Alternative für die Tiefenbestimmung von Defekten bei Messungen mit langen Erwärmungs- und Beobachtungszeiten, wie sie bei Anwendung von aktiver Thermografie im Bauwesen häufig vorkommen.
Abstract
In the recent years the application of infrared thermography and especially its active approaches lock-in thermography, impulse themography and pulse phase thermography (PPT) has gained more importance for non-destructive testing (NDT). In this paper it is demonstrated that PPT is very well suited for NDT in civil engineering. The method is based on pulse heating of the investigated specimen and on the observation of the cooling down process on its surface with an infrared camera. The transient behaviour is afterwards analysed with Fast Fourier Transformation, enabling the creation of phase and amplitude images with enhanced visualisation of the defects. Results of European and National (i.e. DFG) funded projects are presented, for example the detection of voids and inhomogeneities close to the surface and the localisation of delaminations on plastered concrete and masonry specimen.
ZUSAMMENFASSUNG
Im Rahmen eines von der Deutschen Forschungsgemeinschaft geförderten Vorhabens zur zerstörungsfreien Prüfung im Bauwesen wird in der Bundesanstalt für Materialforschung und -prüfung (BAM) in Zusammenarbeit mit der Technischen Universität Berlin (TUB) die Puls-Phasen-Thermografie (PPT) weiterentwickelt, bewertet und eingesetzt. Die durch die Impuls-Thermografie (IT) aufgenommenen Daten werden mittels Fast Fourier Transformation (FFT) bearbeitet. Die durch die FFT gewonnenen Phasenbilder reduzieren die Störeinflüsse von Oberflächeninhomogenitäten und ungleichmäßiger Erwärmung.
Die dargestellten Ergebnisse zeigen deutlich, dass sich die PPT sehr gut zur zerstörungsfreien Prüfung im Bauwesen eignet. Insbesondere Inhomogenitäten im oberflächennahen Bereich, wie Ablösungen und Hohlstellen hinter Beschichtungen (Putz, CFK-Laminate etc.), aber auch Defekte in größeren Tiefen können zuverlässig geortet und bildgebend dargestellt werden.
Die Fahrzeug-Fahrweg-Untergrund-Wechselwirkung bei der Festen Fahrbahn und beim Schottergleis
(2002)
Seismic response of three-dimensional structures using a green's function approach to the soil
(1986)
A finite-element boundary-element software for the dynamic interaction of flexible structures and the soil has been extended for pile foundation. The boundary element method for the soil uses the Green´s functions of the layered half-space which have been generalised for interior loads. Pile groups of 10 to 20 piles of different arrays are analysed and compared with single piles. Simplified models have been developed for a user-friendly, practice oriented prediction software for railway induced ground and building vibration.
The present contribution evaluates four measuring series made by the Federal Institute of Material Research and Testing for the relations between train speed and ground vibration amplitudes. This experimental evaluation is supported by the simulation of the train passages at the different sites by using appropriate excitation mechanisms and forces as well as layered soil models which have been derived from impact measurements at each site.
Seit 25 Jahren betreibt die Bundesanstalt für Materialprüfung intensive Forschung auf dem Gebiet der Eisenbahndynamik unter realistischer Einbeziehung des Gleisuntergrundes. Das umfaßt theoretisch/numerische Arbeiten, Feldmessungen und Labor-, Modell- und Elementversuche zu den folgenden Fragen:
-die Erschütterungs- und Körperschallweiterleitung durch den natürlichen Boden,
- das Schwingungsverhalten der verschiedenen Fahrwege auf speziellen Boden- und Schotterschichten,
- die dynamischen Kräfte während der Überfahrt des Fahrzeugs sowie
- das Setzungs- und Differenzsetzungsverhalten verschiedener Gleisstrukturen.
Es werden Rechen- und Meßergebnisse zum Vergleich der Festen Fahrbahn und des Schottergleises vorgestellt und daraus Möglichkeiten für die weitere Verbesserung von Bahnfahrwegen gefolgert. Eine wesentliche Rolle kommt dabei der Wechselwirkung von Platten und steifen Declcschichten mit dem umgebenden Boden zu, deren Theorie in der BAM in den 90er Jahren weiterentwickelt wurde.
Fahrzeug-Fahrweg-Untergrund-Umgebung: theoretische, rechnen- und meßtechnische Untersuchungen
(1987)
The ground vibrations, which are generated by trains on different tracks, have been calculated by finite-element boundary-element models. The ballasted track is modelled in detail by the finite element method. The infinite soil is modelled by the boundary element method as a homogeneous or layered half-space. The track-soil system is coupled to a simple rigid mass model of the vehicle so that the vehicle-track interaction is completely included. Transfer functions are calculated in frequency domain without and with vehicle-track interaction, the compliance of the track and the mobilities of the soil at different distances from the track. Finally, the ratios between the ground vibration amplitudes with and without mitigation measures are calculated to quantify the effectiveness of the mitigation measures.
Tracks with under-sleeper pads have been investigated in a wide parameter study for the RIVAS project. The main parameters that influence the reduction of ground vibration are the stiffness of the under-sleeper pad, the mass and the width of the sleeper. The softest sleeper pad yields the best reduction of the ground vibration. The influence of the sleeper mass is not so strong, as the characteristic frequency is ruled by the mass of the sleeper and the mass of the wheelset as well.
This contribution presents experimental methods to detect track damage. At BAM (Federal Institute of Material Research and Testing), a measuring car with a measuring system of 72 channels, geophones, mountings, cables, harmonic and impulsive exciters is used for dynamic measurements of the track, the soil and buildings. An instrumented hammer allows force measurements and to evaluate transfer functions of the track, and the soil. Wave measurements are used to identify the soil characteristics. Train passages are measured at the track and for the train induced ground vibrations. In addition to these in situ options, tests of tracks or track elements can be performed in a large laboratory.
Schwingungsminderung zwischen Quelle und Empfänger - FEM-Berechnung der Wellenausbreitung im Boden
(2006)
Die Ausführung von Abdichtungssystemen insbesondere an Ingenieurbauwerken der Verkehrsinfrastruktur greift in die unmittelbare Verfügbarkeit/Nutzbarkeit des Bauwerks ein und erfolgt deshalb i.a.R. unter höchstem Zeitdruck. Neuere materialtechnische Entwicklungen im Bereich der Flüssigkunststoff-Systeme erlauben kürzere Ausführungszeiten in einem erweiterten Einsatzspektrum. Zur Sicherstellung anforderungsgerechter Gebrauchseigenschaften des gesamten Brückenabdichtungssystems gibt die vorliegende Veröffentlichung Hinweise für die einzuhaltenden Baugrundsätze, bautechnologische Besonderheiten und Erfordernisse im Umgang mit Polymethylmethacrylat (PMMA) sowie qualitätssichernde Maßnahmen.
Verformung und Gefügetransformation bei Schwingungsverschleiß von austenitischen FeCrNi-Legierungen
(2004)
Influence of variable polarity pulsed current technique on grain refinement of AZ31 weldments
(2009)
A variety of methods used to prepare nano-objects for surface analysis are described along with information about when they might be best applied. Intrinsic properties of NPs which complicate their characterization and need to be considered when planning for surface or other analyses of NPs are identified, including challenges associated with reproducible synthesis and functionalization of the particles as well as their dynamic nature. The relevant information about the sample preparation processes, along with analysis details and data that need to be added to the collection of material provenance information is identified. Examples of protocols that have been successfully used for preparation of nano-objects for surface analysis are included in an annex.
Der vorliegende Beitrag befasst sich mit dem internationalem Status der Ermittlung und Verfügbarkeit dynamischer Bruchzähigkeitswerte ferritischer Gusseisenwerkstoffe mit Kugelgraphit. Einleitend wird der Stand bruchmechanischer Prüfnormen hinsichtlich der Definition von Kennwerten bei dynamischer Beanspruchung analysiert. Zur dynamischen Bruchzähigkeit von ferritischem Gusseisen mit Kugelgraphit wurde eine Datenbasis erstellt, die den aktuellen veröffentlichten Stand auf diesem Gebiet widerspiegelt und eine Vielzahl unterschiedlicher von den Autoren verwendeter Kennwertdefinitionen enthält. Daher ist eine systematische Auswertung dieser Datenbasis sehr schwierig. Zur Veranschaulichung des temperaturabhängigen Bruchverhaltens wurde jedoch eine Reihe von zusammenfassenden graphischen Darstellungen erarbeitet. Anhand derer wird der Informationsgehalt einzelner Kennwertgruppen diskutiert und deren Aussagekraft für den Fall einer Bauteilsicherheitsbewertung eingeschätzt.
Dynamic fracture mechanics characteristics are required for design and safety proof of advanced
ductile cast iron (DCI) components. In this paper, the analytical compliance ratio
(CR) and numerical finite element (FE) key curve methods were investigated for dynamic Rcurve
testing. Two DCI materials, a purely ferritic and a ferritic one with 18 % of pearlite,
were tested at room temperature (RT) and -40 °C. The special focus is on the impact of the
materials damage and fracture behaviour on performance and limitations of the investigated
methods.
Systematic metallographic and fractographic microstructural analyses were performed accompanying
the test program. Summarizing systematics of the specific damage behaviour
and fracture mechanisms were developed taking microstructure, loading rate, specimen geometry
and test temperature into account.
There has been a change from ductile to brittle fracture mechanism observed at -40 °C with
ferritic DCI and even at RT with ferritic-pearlitic DCI. The ferritic-pearlitic DCI did not show Rcurve
behaviour at -40 °C and only single Juc values could be determined. Furthermore, with
ferritic-pearlitic DCI, random pearlite shares in the ligament caused the relation between
loading rate, force-deflection record and crack extension not to remain uniquely defined.
Therefore, the FE key curve method proofed not to be applicable since the FE model was
based on homogeneous isotropic material and ductile failure mode only. The analytical CR
key curve method worked well only with selected combinations of microstructure, specimen
geometry and temperature.
In summary it has to be concluded that a robust, accurate and sufficiently simple dynamic
key curve method that was suited for application in quality control of industrial relevant DCI
qualities cannot be provided currently.
Application of electronic nose and ion mobility spectrometer to quality control of spice mixtures
(2009)
Our earlier study based on historical and scientific analysis showed that Iranians used a considerable range of materials in the sizing process. Unlike many nations who used limited sizing materials to improve the mechanical strength and to smoothen the paper surface, Iranians have used various materials for sizing process from Taimurid (15th century) to Safawid (16th century) and Qajar (19th century) periods. Further to our earlier study on the Sizing Materials used in Persian manuscripts and miniature paintings, scientific analysis was carried out to investigate their behaviour against the mould fungus Aspergillus flavus. In the first stage fourteen different sizing materials that was identified from Persian historical recipes were reconstructed. In the second stage fungicidal property of each sizing samples against Aspergillus flavus fungus were identified that will be presented in this paper.