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- Zerstörungsfreie Prüfung im Bauwesen (3)
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- Bauwerkserhaltung/Sanierung (1)
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- Brettschichtholz (1)
- Brücken (1)
- Chloridinduzierte Korrosion (1)
- Cu catalysts (1)
- Data Fusion (1)
- Data fusion (1)
- Datenfusion (1)
- EFIT Modelling (1)
- EFIT-modeling (1)
- Elastic wave propagation (1)
- Elastische Wellenausbreitung (1)
- Elastodynamic Finite Integration Technique (EFIT) (1)
- Elastodynamische Finite Integrationstechnik (1)
- Elastodynamische Finite Integrationstechnik (EFIT) (1)
- Electrochemical CO2 conversion (1)
- FT-SAFT (1)
- Flaw characterization (1)
- Footbridge (1)
- Fügestellen (1)
- Grating lobe reduction (1)
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- Grouting faults (1)
- High rate tension test (1)
- Hochgeschwindigkeitszugversuch (1)
- Hohlkastenbrücke (1)
- Holz (1)
- Holzbauteile (1)
- Hüllrohr (1)
- Imaging methods (1)
- Instandsetzung (1)
- Inverse scattering (1)
- Joints (1)
- Kennwerte für Crashsimulation (1)
- Large Aperture Ultrasonic System (1)
- Maize (1)
- Modeling (EFIT) (1)
- Modeling of wave propagation (1)
- Modellierung elastischer Wellen (1)
- Modelling (1)
- Multi-target analysis (1)
- Mycotoxins (1)
- NDT (1)
- Non-destructive testing in civil engineering (1)
- Non-destructive testing in civil engineering (NDT-CE) (1)
- Numerical modelling (1)
- Numerische Modellierung (1)
- One way (1)
- Phased Array (1)
- Phased array (1)
- Polarimetric imaging (1)
- Polarimetrische Abbildungsverfahren (1)
- Polimetrische Abbildungsverfahren (1)
- Post-tensioned concrete (1)
- Potentialmessung (1)
- Pre-stressed concrete (1)
- Prestressed concrete bridges (1)
- Properties for crash simulation (1)
- Prüfkopf (1)
- Pulse echo technique (1)
- Qualitätssicherung (1)
- Reconstruction calculation (SAFT) (1)
- Reconstruction software (1)
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- Rekonstruktionssoftware (1)
- Ringversuch (1)
- Risse (1)
- Round robin (1)
- SAFT reconstruction (1)
- SAFT-Rekonstruktion (1)
- SAR (1)
- Schallfeld (1)
- Scherzugversuch (1)
- Shear tension test (1)
- Spannkanal (1)
- Stable isotope dilution assay (1)
- Stahlbeton (1)
- Synthetic Aperture Focusing Technique (1)
- Synthetic aperture focusing technique (SAFT), (1)
- Tandem mass spectrometry (1)
- Tendons (1)
- Time reversal (1)
- Transversalwellen (1)
- Ultrahigh-performance liquid chromatography (1)
- Ultraschall-Echo (1)
- Ultraschallecho-Methode (1)
- Ultrasonic NDT (1)
- Ultrasound "Large Aperture" NDT Concrete (1)
- Ultrasound echo method (1)
- Ultrasound imaging (1)
- Verpresszustand (1)
- W-Cl (1)
- Wellenausbreitung (1)
- X-ray absorption spectroscopy (1)
- ZfP-Bau (1)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (3)
We concentrate on appropriate algorithmic processing of microwave Ground Penetrating Radar (GPR) data obtained from concrete specimens containing tendon ducts below steel reinforcement bars either via simulations or via experiments. The goal is to understand the physical phenomena of electromagnetic wave propagation and scattering in detail in order to optimize imaging algorithms like SAFT (Synthetic Aperture Focusing Technique as the NDT version of SAR) in its 3D diffraction tomographic FT-SAFT formulation (Fourier-Transform-SAFT). Therefore we start with the simulation of a "simple" specimen and switch to a more realistic one in order to check whether simulation and experiment can give comparable results. Basically, this could be confirmed, but, nevertheless, various parametric studies will still have to be performed in the future.
Characterization of reflector types by phase-sensitive ultrasonic data processing and imaging
(2008)
Ultrasonic and radar imaging techniques are limited in resolution by the wavelength in the material, yet information beyond those limits is hidden in complex frequency dependent reflection coefficients. The analysis of the phase of complex reflection coefficients together with the properties of imaging algorithms can help to characterize and to classify indications of defects in concrete buildings. This paper describes a method to extract phase information from measurements and SAFT reconstructed images. The influencing factors like material properties, transducer characteristics, and imaging algorithms based on Born or Physical Optics approximations are elaborated. Simulated and experimental results are briefly discussed.
This paper presents the progress of successful location of grouting faults in tendon ducts with ultrasonic imaging. The examples were obtained in the research group FOR 384 funded by DFG (German Research Foundation). The co-operation of experimental research and modeling allowed imaging and identification of grouted and ungrouted areas of tendon ducts (including strands) in a large test specimen (40 m²). In addition to the criteria for indicating grouting faults in post-tensioned ducts known until now the phase evaluation of reflected ultrasonic pulses is described. Experiments and modeling of wave propagation are presented for reflections at metal plates in concrete (thickness range 0.5 mm to 40 mm) and for tendon ducts including strands.
The main part of the progress was achieved by automated measurements using dry contact transducers, 3D-SAFT reconstruction including phase evaluation and modeling considering wave propagation for typical elastic parameters and exact experimental site conditions. The results for shear waves as well as for pressure waves are compared in the frequency range from 50 kHz to 120 kHz.
There is a great demand for non-destructive testing methods for quality assurance and to assess the safety and durability of wooden structures. Ultrasonic echo technique with shear waves in the frequency range of 50 kHz is one of those promising methods and is already frequently applied for usual and glued laminated timber. The article describes the development and first results for an imaging method for this purpose. The highly anisotropic properties of the ultrasonic velocity have to be considered. A 3D-SAFT (Synthetic Aperture Focusing Technique) imaging scheme is developed initially for synthetic data resulting from modelling the elastic wave propagation. The main part of the paper describes the experimental validation of this evaluation technique by experimental studies applying automated ultrasonic scanning techniques. 3D ultrasonic imaging results are described for test specimens made from pine and spruce wood. Another object of investigation was a pedestrian bridge made from siberian larch.
Dieses Merkblatt beschreibt die Anwendung elektrochemischer Potentialmessungen (häufig auch als Potentialfeldmessung bezeichnet) zur Detektion von Bewehrungsstahlkorrosion an Stahlbetonbauwerken. Mit Hilfe dieses Verfahrens können Bereiche korrodierender Bewehrung zerstörungsfrei lokalisiert werden. In der Regel kommt diese Messmethode bei der Detektion chloridinduzierter Korrosion zum Einsatz. In Abgrenzung hierzu sollte die Abschätzung der Gefahr einer karbonatisierungsinduzierten Korrosion durch Bestimmung der Karbonatisierungstiefe und der Betondeckung erfolgen.
Inhalt ist die zerstörungsfreie Detailuntersuchung von Holzbauteilen mit einem dreidimensional abbildenden Ultraschall-Echoverfahren. Das neu entwickelte 3D-Verfahren berücksichtigt den anisotropen Aufbau des Holzes. Die Bildschnitte und Projektionen werden aus flächigen Ultraschallaufnahmen berechnet. Die Messungen erfolgen an Probekörpern sowie an Bauteilen aus der Praxis. In dem Forschungsvorhaben wird die für Holz neue 3D-Rekonstruktionsrechnung verwendet und mit dem Ziel weiterentwickelt, unter Berücksichtigung der anisotropen Struktur des Holzes eine dreidimensional aufgelöste Abbildung von Reflektoren im Inneren der Holzbauteile zu ermöglichen. Damit werden die bisher für Holzbauteile zur Verfügung stehenden Verfahren entscheidend ergänzt, weil nun eine hochgenaue dreidimensionale Abbildung erreichbar ist (Auflösung: 20 mm und besser).
Electrochemical half-cell potential measurements for the detection of reinforcement corrosion
(2014)
This specification describes the application of electrochemical half‐cell potential measurements (frequently also called potential mapping) for the detection of reinforcement corrosion in reinforced concrete structures. Areas of corroding reinforcement steel can be located in a nondestructive manner by means of this procedure. Half‐cell potential measurements are used in order to detect chloride‐induced corrosion. However, it is not recommended in order to assess the risk of carbonation‐induced corrosion. For this purpose the determination of the carbonation depth and the concrete cover appear to be more appropriate.
The content of this specification exclusively refers to the application of mobile, local variable reference electrodes, which are only placed on the concrete surface while measuring. The technique distinguishes itself thereby from the range of corrosion monitoring systems with stationary installed reference electrodes and sensor systems, respectively, whereby it is possible to continuously track measurements within the area of the installed electrodes. However, these methods are not dealt with in this specification.
Non-destructive testing (NDT) of concrete structures is performed using pulse-echo methods. According to the type of the applied waves it can be classified as acoustic (Impact-Echo, Ultrasonics) and electromagnetic methods (Radar). The results are visualised through different imaging processes. This work is performed in the frame of a research project promoted by Deutsche Forschungsgemeinschaft (FOR384).The objective of data fusion is to use the complementary information of the different methods. Radar can detect metallic reflectors in concrete (metallic ducts and concrete reinforcement) very well. This method is not able to locate defects behind these reflectors (injecting defects, defects behind close concrete reinforcement), because the electromagnetic waves are completely reflected at metals. The acoustic methods are able to compensate this deficit i.e. acoustic waves can penetrate through metal. But acoustic waves in the ultrasonic range are completely reflected by air layers. Air layers have smaller influence on radar propagation, so that both methods complement each other.In order to be able to combine the NDT-data from several methods records at the same volume, the different data setsmodes of signals must be adapted. The ultrasonic and radar data have to be reconstructed with programs based on the Synthetic Aperture Focusing Technique (SAFT) before data fusion. Subsequently, a conversion of the data into a uniform format has to be carried out. This is a prerequisite in order to keep the data exchange between the project partners as simple as possible. After the data sets are imported and transferred into a common reference system, they can be processed with operations according to the purpose of the investigation. Results, which have been achieved in concrete test specimen with radar and ultrasonics, will be presented and will show the feasibility of the data fusion method.
Stable isotope dilution assay for the accurate determination of mycotoxins in maize by UHPLC-MS/MS
(2012)
A fast, easy-to-handle and cost-effective analytical
method for 11 mycotoxins currently regulated in maize and
other cereal-based food products in Europe was developed
and validated for maize. The method is based on two extraction
steps using different acidified acetonitrilewater mixtures.
Separation is achieved using ultrahigh-performance
liquid chromatography (UHPLC) by a linear watermethanol
gradient. After electrospray ionisation, tandem mass spectrometric
detection is performed in dynamic multiple reaction
monitoring mode. Since accurate mass spectrometric quantification
is hampered by matrix effects, uniformly [13C]-
labelled mycotoxins for each of the 11 compounds were added
to the sample extracts prior to UHPLC-MS/MS analysis.
Method performance parameters were obtained by spiking
blank maize samples with mycotoxins before as well as after
extraction on six levels in triplicates. The twofold extraction
led to total recoveries of the extraction steps between 97%and
111% for all target analytes, including fumonisins. The [13C]-
labelled internal standards efficiently compensated all matrix
effects in electrospray ionisation, leading to apparent recoveries
between 88% and 105% with reasonable additional costs.
The relative standard deviations of the whole method were
between 4% and 11% for all analytes. The trueness of the
method was verified by the measurement of several maize test
materials with well-characterized concentrations. In conclusion,
the developed method is capable of determining all
regulated mycotoxins in maize and presuming similar
matrix effects and extraction recovery also in other cerealbased
foods.