Filtern
Dokumenttyp
Schlagworte
- Digitale Radiologie (2)
- Fibre composites (2)
- Laminografie (2)
- Materialgeschichtliches (2)
- Mobile Anwendungen (2)
- Tomographie (2)
- Aerospace (1)
- Analyse (1)
- Austenite (1)
- Backscatter (1)
Mobile Tomographic Computer Aided Radiometry (TomoCAR) is based on the mechanical position control of an X-ray tube in front of an object and the application of a Digital Detector Array (DDA) behind it. Several hundred radiometric projections in small angle steps are acquired during the controlled movement of the X-ray tube along a preselected way. The tomographic or laminographic reconstruction allows the three-dimensional (3D) representation of flaws. A specially designed radiometric detector array with small internal unsharpness and high image contrast was used for visualization and sizing of planar and volumetric defects in austenitic welds in nuclear power plants. A German pilot study was successfully performed on the basis of the European network of inspection and qualification (ENIQ) guidelines. This was the precondition for several applications of TomoCAR in nuclear power stations in Germany and Switzerland.
A versatile computed tomography (CT) system was developed on basis of the TomoCAR design for in situ inspection of large aircraft components under production conditions. A gate based planar computed tomograph was constructed and tested for inspection of the integrity of CFRP stringers, embedded in aircraft fibre composite shells. A probability of crack visibility >90% could be determined.
Wood is the material that has accompanied the whole development of mankind in various applications, for manufacturing tools and weapons, for buildings and constructions and also as fuel. It has various appearances and is subjected to decomposing changes, so there are sufficient arguments for non-destructive testing of wooden objects in the same way as is common practice with other technologically used materials. However, even today wood is rarely tested. Moreover, artefacts of cultural heritage containing wood are rare and delicate, so dismantling these for studying purposes is undesirable. Radiological inspection technologies are the methods of choice to provide a non-destructive insight. Interrogations of a specimen with various kinds of radiation provide different answers about their internal structures. High-quality detailed images are achievable with X-rays or gamma radiation in cases where heavy metals or other dense materials are not involved. Neutrons behave complementarily; they are avidly absorbed by light elements such as hydrogen on the one hand and yet are capable of easily penetrating heavy metals on the other. This provides an alternative for X-ray radiography and tomography when material characteristics are of primary interest rather than structural details, or when shielding with plates or sleeves of heavy metal severely impedes inspections with X-ray or gamma radiation technologies. However, due to the moderating effect of wooden samples it is essential to use fast neutrons for radiography and tomography of voluminous objects. Some typical examples described here will show the difference between neutron and X-ray photon-based radiographic technologies.
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.
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.