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- 2015 (24) (entfernen)
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- Active thermography (4)
- Aktive Thermografie (4)
- Non-destructive testing (3)
- Aluminium (2)
- Lockin-Thermography (2)
- Photogrammetrie (2)
- Zerstörungsfreie Prüfung (2)
- 3D-Kartierung (1)
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Eingeladener Vortrag
- nein (11)
Die messtechnische Erfassung von Bauwerkschäden ist eine wichtige Voraussetzung für die dreidimensionale und zeitaufgelöste Darstellung von möglicherweise sicherheitsrelevanten Veränderungen an Bauwerken, wie z. B. Verformungen, Verwindungen und Risswachstum. Ziel des vorgestellten Projektes war die Entwicklung eines Verfahrens zur effizienten und wiederholbaren 3D-Schadenkartierung an zum Teil empfindlichen Bauteiloberflächen.
Aktive Thermografie mit Lockin-Anregung ist ein zerstörungsfreies Prüfverfahren, das insbesondere auch die Prüfung von kohlenstofffaserverstärkten Kunststoffen ermöglicht. Um eine Standardisierung dieses Verfahrens voranzubringen, wurden im Rahmen eines Forschungsprojektes umfangreiche Untersuchungen zur Validierung des Verfahrens durchgeführt. Für die Anregungsmethoden optisch und Ultraschall wurden die wichtigsten Parameter systematisch untersucht. Auf der Auswertungsseite ist dies z.B. der Einfluss der spektralen Empfindlichkeit verschiedener Kamerasysteme. Für die Anregungen sind unter anderem die Einflüsse von Anregungsenergie und Ultraschallfrequenz untersucht worden. Auch Materialparameter, wie der Lagenaufbau bei CFK-Probekörpern, beeinflussen die Ergebnisse stark.
Cooling-down of thermal thick probes after flash excitation - A measure for the real energy density?
(2015)
Though flash lamps are one of the most applied heat sources in the field of Thermographic Testing (TT) using active thermography, only little is known about the actually achieved energy input into test objects. In this paper, an easy to realize sensor concept is proposed and experimentally evaluated. The concept is based on the measurement of the surface temperature of a thermal thick probe after flash excitation. After considering the sensor concept with FEM simulations the experimental investigation of four materials (two polymer and two building materials) is described. It will be shown that a suited coating is essential for the realization of the sensor concept. The experimental results prove the suitability of black rigid PVC as the most promising material. Using a coated PVC sample the energy density of short laser pulses, similar to flashes of flash lamps, could be determined exactly with an estimated relative uncertainty of only a few percent.
In this contribution, the development and application of optical and thermographic methods for the nondestructive evaluation of delaminations, cracks and further substructures in Connection with bulging is presented.
Since delaminated fagade elements show geometric as well as thermal anomalies, surface geometry and defects beneath the surface were investigated. As methods, Stereo photogrammetry, a tracking based method for tactile recording of geometric 3D data and active thermography were used. Two case studies were assessed with a combination of these methods: the plaster scratches at the Magdeburg Cathedral and a mural painting in Cobbelsdorf, both located in Germany. While the plaster scratches have been investigated by artificial heating with an infrared radiator, the rural painting was tested by analysing the temperature increase due to solar heating.
Lockin thermography is a well-suited method for the characterization of structures made of both metal and fiber reinforced plastic. In most cases, only phase images are analyzed, although the amplitude images might contain useful information as well. Thus, systematic studies of lockin thermography are presented, assessing amplitude and phase images for the detection and quantification of defects in isotropic (steel) and anisotropic (carbon fiber reinforced plastic) materials. Characterized defects are flat bottom holes with different diameters and various remaining wall thicknesses as well as crossed notches at different depths. The excitation frequency was varied while keeping the number of analyzed excitation periods nearly constant for each material. The data analysis was focused on the detectability of the defects both in the amplitude and phase images, including the determination of the signal-to-noise ratio and of the spatial resolution. As a result, the limits of defect detectability and spatial resolution are given for each material