Filtern
Erscheinungsjahr
Dokumenttyp
- Beitrag zu einem Sammelband (37) (entfernen)
Referierte Publikation
- nein (37)
Schlagworte
- Zerstörungsfreie Prüfung (5)
- POD (4)
- Radar (4)
- Radiografie (4)
- Digitale Radiologie (3)
- Strukturaufklärung (3)
- Videoskopie (3)
- Austenitic Tube Welds (2)
- Baudenkmäler (2)
- Crack inspection (2)
Threat detection and imaging
(2007)
The reliability investigations are dedicated to throw light on the performance of the NDE system with
respect to the required aim. This is especially of interest when digitized and processed signals are
involved where it becomes hard to assess whether the quality of the system has raised or not. Three
different ways to investigate reliability of NDE signals will be described. The first way of investigation,
the performance demonstration, is preferred e.g. in the US American nuclear power industry. This is an
integral consideration of the non destructive test as a system where the whole NDE system is packed in a
black box and only the input in terms of the real existing flaws in the component is considered and
compared to the output in terms of the indications of the human inspector or of the automated system.
The second the European tradition relies on a standardized description of physical/technical
parameters of the NDE system which are preconditions for successful system performance. An example
for such a standardized set of performance parameters is given in the recently released standard about Xray
film digitization CEN EN 14096. The third approach the modular conception is a marriage of
both: The signal chain is cut into main modules. Each module is assessed in a most appropriate
individual way e.g. via modeling calculations. The single results are joint together according to the
reliability of the subsystems. Separating criteria for the system were proposed through a reliability
formula developed during a series of European-American workshops on NDE reliability. Examples of
all three approaches will be given.
Throughout human history, wood has been used for various purposes: for
building shelters, houses and bridges, for manufacturing furniture and
household or agricultural appliances (from ploughs to spoons), as burning
material or simply as walking sticks. Contemporarily, vast amounts of wood
are going into paper production. As a consequence, different qualities of
wood are selected appropriately for the various applications. Beams incorporated
into buildings and constructions have to be sturdy and durable;
boards for furniture are supposed to be free of knots or are expected to have
certain ornamental structures. As long as wood is not simply destined for
burning it should be free of undesired knots or internal damages such as rot
or worm holes. Particularly in cases of infestation with wood destroying
fungi that definitely impairs mechanical strength and even may generate
hollows such damages are frequently invisible from the outside. Radiographic
methods are capable to detect internal damages as well as hidden
knots without the need of drilling holes or cutting a specimen to pieces.
The most thoroughly method to visualise the interior of a wooden specimen
is tomography which shows annual growth rings in their complete circumference
and all the knots or damages that might be included. However, some
of them as well as patterns of annual rings suitable for dendrological investigations
are recognisable with a less laborious method that might be applicable
even in the field, i.e. contemporary digital radiography combined with
image processing. Samples of lumber shall be presented showing the typical
annual ring structures and some infested areas.
Digital detectors such as phosphor imaging plates (IP) and digital detector arrays (DDA) allow radiographic inspection with higher efficiency and improved image quality in comparison to the classic film technique. Mobile X-ray flash tubes are used routinely for veterinarian and security applications. New high sensetive IPs and DDAs enable to apply them for inspection of light materials with low X-ray attenuation as in aluminium, plastics and composites. A versatile computed tompgraphy (CT) system was developed for in situ inspection of large aircraft components under production conditions. A gate based planar computed tomograph wsa developed and testes for inspection of integrety of the stringer incorporation. Successful test trials were performed to prove the detection rate of cracks in embedded stringers. Honey comb structures of aircrafts have to be inspected for water inclusions during in-service inspections. Thermography is a powerful method for in house inspections when variations in temperature caused e. g. by sunshine can be excluded. A new X-ray diaphragm was developed for mobile back scatter measurements of large components. This method is insensitive to heat alterations in the field and thus can be applied also outdoors.
In diesem Beitrag wird die Anwendung von Radiographiesystemen zum Auffinden von Holzschäden beschrieben. Die Anlage besteht aus einer mobilen Röntgenblitzröhre und einem digitalen Radiographiesystem mit Speicherfolie oder einem Flachdetektor. An Hand der durchgeführten Versuche an Laub- und Nadelbäumen sowie an Eichenbalken der Marienkirche der Lutherstadt- Wittenberg wird die Detektion innerer Schäden gezeigt.
Tomographical Computer Aided Radiology (TomoCAR) is based on the mechanical position control of
an X-ray tube in front of a welding seam and the application of a planar array detector behind it. Several hundred
radiometric projections in small angle steps are acquired. The tomographical reconstruction allows the three-dimensional
(3D) representation of the defects. A new radiometric array detector system with a small internal
unsharpness and high image contrast is used for the 2- and 3-dimensional visualization and sizing of planar defects
with a defect opening of less than 100 µm. This detector is based on a CMOS-flat panel with a direct converting
CdTe-single crystal layer. The small design allows the application of the mobile testing equipment for mechanized
X-ray inspection in industrial plants. The physical pixel size of the detector amounts to 0,1x0,1 mm². Nevertheless,
this system yields a better spatial resolution than indirect converting detectors (e.g. cameras with fluorescence
layers of Gd2O2S). It allows the reliable detection of planar defects with openings far below the detector pixel size
by subpixel resolution.
'TomoCAR' is qualified at present in the context with a German pilot study following to the ENIQ guidelines for
the employment within the nuclear power industry.
Zusammenfassung
Der Prototyp einer Flachröntgenröhre mit einer maximalen Röntgenenergie von 240kV (600W) und einer Brennfleckgröße von 0,4 * 0,4 mm nach DIN EN 12543 wird vorgestellt. Das Design dieser Flachröntgenröhre mit geringer Aufbauhöhe ist in Metall-Keramik-Technik ausgeführt. Die Beschleunigungsstrecke Katode-Anode ist senkrecht zur Haubenachse ausgeführt. Die Röhre ist als bipolares System aufgebaut. Kleine Durchmesser der Hochspannungskabel verringern das Gewicht und resultierende Kraftmomente bei der manuellen Manipulation sowie beim Verfahren in einem mechanisierten System. Der Targetwinkel beträgt 6° und bewirkt eine höhere Brillianz der Röntgenstrahlung. Die Geometrie des Strahlenaustrittsfensters (Emissionsfenster) ist in Fächerstrahlgeometrie zur tomografischen Prüfung ausgelegt.
Mechanisierte Durchstrahlungsprüfung - Innovative Techniken zur Bewertung von Rundschweißnähten
(2001)
The quantitative measurement of kind, positions and diameters of steel reinforce ments in building constructions is a typical inspection problem in civil engineering. A classical solution is the combination of film radiography with the multi angle technique and graphical backprojection. New digital detectors reduce the exposure time and allow the application of stereo radiography and computed laminography as routine applications.
The computed laminography allows fast and effectively the determination of the depth of reinforcements in concrete or masonry. A selected area of the steel re-bar structure is penetrated by gamma-rays from different angles of incidence (multi angle-technique) with a Co-60-source. Instead of a radiographic film phosphor imaging plates were used as a new digital medium for filmless radiography. A 3D-image of the measured region of interest is reconstructed from the digitised projections of a test block. The reconstruction is based on special tomosynthesis algorithms which need few projections only.
Radiographic techniques were uses in completion to other techniques like radar, electromagnetic alternating field inspection to examine the structure of different buildings. Experiences of inspections of historical buildings, ancient marble structures and a bridge girder are presented where different levels of radiography were applied.