We present novel multi-energy X-ray imaging methods for direct radiography and computed tomography. The goal is to determine the contribution of thickness, mass density and atomic composition to the ...measured X-ray absorption in the sample. Algorithms have been developed by our own to calculate new X-ray images using data from an unlimited amount of scans/images of different tube voltages by pixelwise fitting of the detected gray levels. The resulting images then show a contrast that is influenced either by the atomic number of the elements in the sample (photoelectric interactions) or by the mass density (Compton scattering). For better visualization, those images can be combined to a color image where different materials can easily be distinguished. In the case of computed tomography no established true multi-energy methodology that does not require an energy sensitive detector is known to the authors. The existing dual-energy methods often yield noisy results that need spatial averaging for clear interpretation. The goal of the method presented here is to qualitatively calculate atomic number and mass density images without loosing resolution while reducing the noise by the use of more than two X-ray energies. The resulting images are generated without the need of calibration stan-dards in an automatic and fast data processing routine. They provide additional information that might be of special interest in cases like archaeology where the destruction of a sample to determine its composition is no option, but a increase in measurement time is of little concern.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Aero-engines operating in dust-laden environments often encounter a lot of dust/sand that causes a severe problem to the TBCs by means of erosion. As the turbine entry temperatures are rising, molten ...sand is also a big concern to the life-time of TBCs.
This paper deals with the TBC behavior under the combined influence of erosion and corrosion attack. Variations in TBC morphology, CMAS infiltration time and CMAS composition and their influence on the erosion resistance at room temperature were investigated. Two different EB-PVD 7YSZ morphologies consisting of a different porosity arrangement were tested in the erosion/corrosion regime. The more ‘Feathery’ structure has a better resistance to erosion compared to a more columnar ‘Normal’ structure, which leads to less degradation of the TBC. However, under the influence of CMAS infiltration the effect was found to be reversed. In general, CMAS-infiltrated EB-PVD TBCs exhibit a higher erosion resistance than the non-infiltrated ones.
X‐Ray White Beam Interferences on Thin Crystals Heckert, Mirko; Enghardt, Stefan; Bauch, Jürgen
Crystal research and technology,
October 2021, 2021-10-00, Letnik:
56, Številka:
10
Journal Article
Recenzirano
Odprti dostop
Results of white beam X‐ray interference measurements on almost perfect semiconductor wafers are presented. A specific measurement geometry allows for the investigation of diffraction effects on thin ...wafers down to at least 375 µm with a simple experimental setup (standard lab CT with microfocus X‐ray tube). Furthermore, the dynamic diffraction effect of double refraction has been studied in detail for thicker samples. This might lead to a new wafer testing method as the observed dynamic effects are very sensible on crystal quality.
Results of white beam X‐ray interference measurements on almost perfect semiconductor wafers are presented. A new measurement geometry allows for the investigation of thin wafers. In this geometry, double refraction inside the sample, a dynamic diffraction effect, can be observed with a simple experimental setup and has been studied in detail. This might lead to a new wafer testing method.
Additive manufacturing technologies, particularly electron beam powder bed fusion (PBF‐EB/M), are becoming increasingly important for the processing of intermetallic titanium aluminides. This study ...presents the effects of hot isostatic pressing (HIP) and subsequent two‐step heat treatments on the microstructure and mechanical properties of the TNM‐B1 alloy (Ti–43.5Al–4Nb–1Mo–0.1B) fabricated via PBF‐EB/M. Adequate solution heat treatment temperatures allow the adjustment of fully lamellar (FL) and nearly lamellar (NL‐β) microstructures. The specimens are characterized by optical microscopy and scanning electron microscopy (SEM), X‐ray computed tomography (CT), X‐ray diffraction (XRD), and electron backscatter diffraction (EBSD). The mechanical properties at ambient temperatures are evaluated via tensile testing and subsequent fractography. While lack‐of‐fusion defects are the main causes of failure in the as‐built condition, the mechanical properties in the heat‐treated conditions are predominantly controlled by the microstructure. The highest ultimate tensile strength is achieved after HIP due to the elimination of lack‐of‐fusion defects. The results reveal challenges originating from the PBF‐EB/M process, for example, local variations in chemical composition due to aluminum evaporation, which in turn affect the microstructures after heat treatment. For designing suitable heat treatment strategies, particular attention should therefore be paid to the microstructural characteristics associated with additive manufacturing.
Herein, the effects of hot isostatic pressing (HIP) and subsequent two‐step heat treatments on the microstructure and mechanical properties of the TNM‐B1 alloy fabricated via electron beam powder bed fusion (PBF‐EB/M) are investigated. While lack‐of‐fusion defects are the main causes of failure in the as‐built condition, the mechanical properties in the heat‐treated conditions are predominantly controlled by the microstructure.
The piezoelectric materials langasite (LGS) and calcium tantalum gallium silicate (CTGS) have been investigated with the X‐ray rotation tilt (XRRT) technique using a new evaluation method. The XRRT ...technique is a microdiffraction method where diffraction lines are registered on a two‐dimensional detector. These lines can be described using conic sections analogous to Kossel lines. Their form and position depend upon the lattice parameters and orientation of the investigated crystal. They can, therefore, be used to obtain these parameters. The new evaluation method allows for an automatic indexing of XRRT and Kossel reflections without knowledge of the pattern centre and detector‐to‐sample distance. This enables the investigation of more complex crystal structures like LGS and CTGS, where in this work the lattice constants and orientation were measured at various points on the sample.
A high‐precision lattice constant determination of piezoelectric langasite and calcium tantalum gallium silicate crystals using the X‐ray rotation tilt technique combined with a new evaluation method is presented.
Nichtmetallische Bewehrungen werden bereits heute vielfältig im Betonbau eingesetzt. Bisher erfolgt deren Materialprüfung überwiegend unter zerstörenden Bedingungen. So wird die Position der ...Bewehrungslagen innerhalb der Betonmatrix durch Sichtung und Vermessung von Sägeschnittflächen ermittelt. Bildgebende Verfahren wie Röntgen‐Computertomografie (X‐ray computed tomography, XCT) und ‐laminografie (X‐ray computed laminography, XCL) ermöglichen die zerstörungsfreie Bewertung und Ortung von Bewehrungsmaterialien aus bspw. Carbon‐ und Glasfaser innerhalb eines Betonkörpervolumens. Die Betondeckung sowie der Garnquerschnitt, ‐abstand und die Lage der Bewehrung ließen sich in der Betonmatrix durch XCT sichtbar machen und Letztere mit einer Abweichung von < 0,2 mm, im Vergleich zur zerstörenden Kontrollmessung (bisheriges Verfahren) mittels Messmikroskop, bestimmen. Durch eine spezielle Verfahrenskombination aus Limited‐AngleRöntgen‐Computertomografie (LAT) mit anschließender XCL gelang es, die Detailerkennbarkeit der rekonstruierten Schnittbilder gegenüber den Einzelverfahren zu erhöhen.
Nichtmetallische Bewehrungen werden bereits heute vielfältig im Betonbau eingesetzt. Bisher erfolgt deren Materialprüfung überwiegend unter zerstörenden Bedingungen. So wird die Position der ...Bewehrungslagen innerhalb der Betonmatrix durch Sichtung und Vermessung von Sägeschnittflächen ermittelt. Bildgebende Verfahren wie Röntgen‐Computertomografie (X‐ray computed tomography, XCT) und ‐laminografie (X‐ray computed laminography, XCL) ermöglichen die zerstörungsfreie Bewertung und Ortung von Bewehrungsmaterialien aus bspw. Carbon‐ und Glasfaser innerhalb eines Betonkörpervolumens. Die Betondeckung sowie der Garnquerschnitt, ‐abstand und die Lage der Bewehrung ließen sich in der Betonmatrix durch XCT sichtbar machen und Letztere mit einer Abweichung von < 0,2 mm, im Vergleich zur zerstörenden Kontrollmessung (bisheriges Verfahren) mittels Messmikroskop, bestimmen. Durch eine spezielle Verfahrenskombination aus Limited‐AngleRöntgen‐Computertomografie (LAT) mit anschließender XCL gelang es, die Detailerkennbarkeit der rekonstruierten Schnittbilder gegenüber den Einzelverfahren zu erhöhen.
Examination of concrete samples with CFRP and GFRP reinforcement by X‐ray computed tomography and laminography – concrete samples with CFRP and GFRP reinforcement
Non‐metallic reinforcements are already widely used in concrete construction today. Up to now, material testing has mainly been carried out under destructive conditions. As a consequence, the position of the reinforcement within the concrete matrix is determined by inspection and measurement of saw cut interfaces. Imaging procedures as X‐ray computed tomography (XCT) and laminography (XCL) enable the nondestructive evaluation and location of carbon and glass fiber reinforcements within the volume of a concrete structure platform. The concrete cover as well as the yarn cross‐section, spacing and the position of the reinforcement can be determined in the concrete matrix by XCT, the latter with a deviation of < 0.2 mm in comparison with the destructive control measurements of the previous method by means of a measuring microscope. A special combination of limited‐angle X‐ray computed tomography (LAT) followed by XCL has been shown to increase the detailed recognition of the reconstructed sectional images compared to the individual procedures.
Abstract
Nichtmetallische Bewehrungen werden bereits heute vielfältig im Betonbau eingesetzt. Bisher erfolgt deren Materialprüfung überwiegend unter zerstörenden Bedingungen. So wird die Position der ...Bewehrungslagen innerhalb der Betonmatrix durch Sichtung und Vermessung von Sägeschnittflächen ermittelt. Bildgebende Verfahren wie Röntgen‐Computertomografie (X‐ray computed tomography, XCT) und ‐laminografie (X‐ray computed laminography, XCL) ermöglichen die zerstörungsfreie Bewertung und Ortung von Bewehrungsmaterialien aus bspw. Carbon‐ und Glasfaser innerhalb eines Betonkörpervolumens. Die Betondeckung sowie der Garnquerschnitt, ‐abstand und die Lage der Bewehrung ließen sich in der Betonmatrix durch XCT sichtbar machen und Letztere mit einer Abweichung von < 0,2 mm, im Vergleich zur zerstörenden Kontrollmessung (bisheriges Verfahren) mittels Messmikroskop, bestimmen. Durch eine spezielle Verfahrenskombination aus Limited‐AngleRöntgen‐Computertomografie (LAT) mit anschließender XCL gelang es, die Detailerkennbarkeit der rekonstruierten Schnittbilder gegenüber den Einzelverfahren zu erhöhen.
Abstract
Examination of concrete samples with CFRP and GFRP reinforcement by X‐ray computed tomography and laminography – concrete samples with CFRP and GFRP reinforcement
Non‐metallic reinforcements are already widely used in concrete construction today. Up to now, material testing has mainly been carried out under destructive conditions. As a consequence, the position of the reinforcement within the concrete matrix is determined by inspection and measurement of saw cut interfaces. Imaging procedures as X‐ray computed tomography (XCT) and laminography (XCL) enable the nondestructive evaluation and location of carbon and glass fiber reinforcements within the volume of a concrete structure platform. The concrete cover as well as the yarn cross‐section, spacing and the position of the reinforcement can be determined in the concrete matrix by XCT, the latter with a deviation of < 0.2 mm in comparison with the destructive control measurements of the previous method by means of a measuring microscope. A special combination of limited‐angle X‐ray computed tomography (LAT) followed by XCL has been shown to increase the detailed recognition of the reconstructed sectional images compared to the individual procedures.
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