Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (32)
- Beitrag zu einem Tagungsband (23)
- Vortrag (7)
- Posterpräsentation (4)
- Beitrag zu einem Sammelband (3)
- Buchkapitel (1)
Schlagworte
- Computertomographie (8)
- Concrete (7)
- Beton (5)
- X-ray computed tomography (5)
- CT (4)
- Corrosion (4)
- Korrosion (4)
- Computed tomography (3)
- Crack detection (3)
- Micro-computed tomography (3)
Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (19)
- 8.5 Röntgenbildgebung (19)
- 7 Bauwerkssicherheit (3)
- 7.1 Baustoffe (2)
- 8.0 Abteilungsleitung und andere (2)
- 5 Werkstofftechnik (1)
- 5.3 Polymere Verbundwerkstoffe (1)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (1)
- 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen (1)
- 9 Komponentensicherheit (1)
Eingeladener Vortrag
- nein (7)
During the last decades, X-ray (micro-)computed tomography has gained increasing attention for the description of porous skeletal and shell structures of various organism groups. However, their quantitative analysis is often hampered by the difficulty to discriminate cavities and pores within the object from the surrounding region. Herein, we test the ambient occlusion (AO) algorithm and newly implemented optimisations for the segmentation of cavities (implemented in the software Amira). The segmentation accuracy is evaluated as a function of (i) changes in the ray length input variable, and (ii) the usage of AO (scalar) field and other AO-derived (scalar) fields. The results clearly indicate that the AO field itself outperforms all other AO-derived fields in terms of segmentation accuracy and robustness against variations in the ray length input variable. The newly implemented optimisations improved the AO field-based segmentation only slightly, while the segmentations based on the AOderived fields improved considerably.
Additionally, we evaluated the potential of the AO field and AO-derived fields for the separation and classification of cavities as well as skeletal structures by comparing them with commonly used distance-map-based segmentations. For this, we tested the zooid separation within a bryozoan colony, the stereom classification of an ophiuroid tooth, the separation of bioerosion traces within a marble block and the calice (central cavity)-pore separation within a dendrophyllid coral. The obtained results clearly indicate that the ideal input field depends on the three-dimensional morphology of the object of interest. The segmentations based on the AO-derived fields often provided cavity separations and skeleton classifications that were superior to or impossible to obtain with commonly used distance-map-based segmentations. The combined usage of various AO-derived fields by supervised or unsupervised segmentation algorithms might provide a promising target for future research to further improve the results for this kind of high-end data segmentation and classification. Furthermore, the application of the developed segmentation algorithm is not restricted to X-ray (micro-)computed tomographic data but may potentially be useful for the segmentation of 3D volume data from other sources.
The impact of fracture geometry and aperture distribution on fluid movement and on non-reactive solute transport was investigated experimentally and numerically in single fractures. For this purpose a hydrothermally altered and an unaltered granite drill core with axial fractures were investigated. Using three injection and three extraction locations at top and bottom of the fractured cores, different dipole flow fields were examined. The conservative tracer (Amino-G) breakthrough curves were measured using fluorescence spectroscopy. Based on 3-D digital data obtained by micro-computed tomography 2.5-D numerical models were generated for both fractures by mapping the measured aperture distributions to the 2-D fracture geometries (x-y plane). Fluid flow and tracer transport were simulated using COMSOL Multiphysics®.
By means of numerical simulations and tomographic imaging experimentally observed breakthrough curves can be understood and qualitatively reproduced. The experiments and simulations suggest that fluid flow in the altered fracture is governed by the 2-D fracture geometry in the x-y plane, while fluid flow in the unaltered fracture seems to be controlled by the aperture distribution. Moreover, we demonstrate that in our case simplified parallel-plate models fail to describe the experimental findings and that pronounced tailings can be attributed to complex internal heterogeneities. The results presented, implicate the necessity to incorporate complex domain geometries governing fluid flow and mass transport into transport modeling.
The literature has shown that the application of laminography provides advantages as 3D radiographic imaging with depth information for in house and mobile testing. This permits to distinguish between overlapping indications, measure the extension along radiation direction and classify indications as surface open or subsurface
ones as required in critical engineering assessment. This work provides a comparative study and measurements of the three techniques Digital Radiography (DR) with Digital Detector Arrays (DDA), Coplanar Translational Laminography (CTL) and Computed Tomography (CT), applied for composite pipeline inspection. It is demonstrated that CTL and CT provide advantages for the evaluation of pipe-to-pipe connections and the evaluation of adhesive applications. They show indications of discontinuities with higher contrast sensitivity than radiography.
Beyond it, two specimen, namely Phantom 1 and Phantom 2, were developed and manufactured by additive manufacturing to analyze the preferential detection sensitivity and the direction of features and depth information for laminographic measurements. Another goal was to show the laminographic capabilities to distinguish between overlapping discontinuities. CTL is especially suitable for mobile inspection. Special glass fiber reinforced polymer samples (GRP) were manufactured for further analysis and comparisons between the abovementioned techniques. Finally, Phantoms 1 and 2 show the capability of laminography to detect overlapping indications and also show that discontinuities oriented perpendicular to the scan direction have the highest contrast sensitivity for laminographic measurements.
Die Dauerhaftigkeit von Betonbauteilen zu einer messbaren Größe zu machen, ist ein vorrangiges Ziel der Baustoffforschung. Schrumpfen, Schwinden und Temperaturverformungen gefährden bei Hochleistungsbetonen deren Dauerhaftigkeit. Die begleitende messtechnische Deformationsmessung wird daher zu einer unverzichtbaren Methode, Betonrezepturen zielsicher und ökonomisch hinsichtlich der Dauerhaftigkeit zu entwickeln. Ein flexibler Fabry-Pérot-Interferometer-Sensor ermöglicht die messtechnische Erfassung der frühen Deformationsprozesse bereits ab dem Moment des Betoneinbaus. Der Artikel zeigt das Sensorprinzip, Untersuchungen zur In-situ-Referenzierung und zur Rückwirkung des Sensors sowie dessen Einsatzmöglichkeiten in der Baustoff- und Materialforschung. ----------------------------------------------------------------------
The primary intention of construction materials research is to refer the durability of concrete members to a measurable parameter. Setting, shrinkage, and temperature deformations compromise the durability of high-performance concrete. The respective deformation measurement technology is becoming an indispensible method for the targeted and economic development of concrete mixtures with respect to durability. A flexible EFPI sensor enables the survey of early age deformations directly after placing the concrete. The paper deals with the sensor principle, investigations concerning in-situ referencing, and possible effects of the sensor on the matrix as well as its application in the field of materials research.
Different imaging techniques were employed to monitor Full Notch Creep Test (FNCT) experiments addressing environmental stress cracking in more detail. The FNCT is a well-established test method to assess slow crack growth and environmental stress cracking of polymer materials, especially polyethylene. The standard test procedure, as specified in ISO 16770, provides a simple comparative measure of the resistance to crack growth of a certain material based on the overall time to failure when loaded with a well-defined mechanical stress and immersed in a liquid medium promoting crack propagation.
Destructive techniques which require a direct view on the free fracture surface, such as light microscopy and laser scanning microscopy, are compared to non-destructive techniques, i.e. scanning acoustic microscopy and xray micro computed tomography. All methods allow the determination of an effective crack length. Based on a series of FNCT specimens progressively damaged for varied Durations under standard test conditions, the estimation of crack propagation rates is also enabled. Despite systematic deviations related to the respective Imaging techniques, this nevertheless provides a valuable tool for the detailed evaluation of the FNCT and its further development.
Subject of this investigation is the in-situ evolution of pore volume and pore size distribution in Ytong (a porous concrete material) under increasing pressure with two different non-destructive analytical methods: Nuclear Magnetic Resonance (NMR) and X-ray Computed Tomography (CT). For both methods special strain devices to apply external pressure were constructed. The results from the two techniques yield complementary information on the pore size distribution and allows covering different pore size regions.