Filtern
Erscheinungsjahr
- 2012 (20) (entfernen)
Dokumenttyp
- Beitrag zu einem Tagungsband (10)
- Zeitschriftenartikel (7)
- Vortrag (2)
- Posterpräsentation (1)
Schlagworte
- Radiographie (6)
- ZfP (6)
- Bildqualität (5)
- Digitale Detektoren (3)
- Probability of detection (3)
- X-ray imaging (3)
- Computed tomography (2)
- POD (2)
- Reliability (2)
- Simulation (2)
Eingeladener Vortrag
- nein (2)
Flüssige Gefahr- und Brennstoffe sowie explosive Flüssigkeiten werden mittels zeitaufgelöster Terahertz-Spektroskopie (THZ-TDS) in Analogie zu den in der zerstörungsfreien Werkstoffprüfung verwendeten Strategien untersucht. Verschiedene polare Flüssigkeiten (Alkohole, Aceton, Wasserstoffperoxid, Nitromethan), unpolare Flugzeug- und Kraftfahrzeugkraftstoffe sowie organische Lösungsmittel werden in der praxisrelevanten Reflexionsgeometrie berührungs- und zerstörungsfrei im Zeitbereich charakterisiert. Die Absorptions- und Brechungsindizes einer repräsentativen Auswahl von Flüssigkeiten wurden im Frequenzbereich zwischen 0.1 THz und 1.1 THz unter Verwendung der Transmissionsanordnung spektral ermittelt. Die Messkonfiguration wird für stark und schwach absorbierende Flüssigkeiten jeweils angepasst.
A time domain spectrometer T-ray 2000® operating in the range of 0.2-2 THz was used for Time of Flight measurements. A series of ethanol water mixtures from 10% to 90% were produced subsequently filled in polystyrene cells and analyzed in the T-ray 2000 TDS system in the reflection mode. The reflectivity of the material liquid interface is strongly influenced by the ethanol concentration in water. The reciprocal reflection coefficient of the material liquid interface was found to be a useful discriminating feature for further Probably of Detection calculations which can be used for the performance evaluation of potential THz bottle scanners. THz pulse echo (PE) measurements were performed in comparison to the established ultra sound PE technique for flaw detection of plastics. Synthetic aperture reconstructions were applied for simulated data to reconstruct the flaw shape. The results were compared with B-scan images of a high density polyethylene (HDPE) test cylinder. Existing restrictions on the quality of the back projected images and limits of the existing model are discussed in detail.
Within the framework of the European project PICASSO, the radiographic simulator aRTist (analytical Radiographic Testing inspection simulation tool) developed by BAM has been extended for reliability assessment of film and digital radiography. NDT of safety relevant components of aerospace industry requires the proof of probability of detection (POD) of the inspection. Modeling tools can reduce the expense of such extended, time consuming NDT trials, if the result of simulation fits to the experiment. Our analytic simulation tool consists of three modules for the description of the radiation source, the interaction of radiation with test pieces and flaws, and the detection process with special focus on film and digital industrial radiography. It features high processing speed with near–interactive frame rates and a high level of realism. A concept has been developed as well as a software extension for reliability investigations, completed by a user interface for planning automatic simulations with varying parameters and defects. Furthermore, an automatic image analysis procedure is included to evaluate the defect visibility. The radiographic modeling from 3D CAD of aero engine components and quality test samples are compared as a precondition for real trials. This enables the evaluation and optimization of film replacement for application of modern digital equipment for economical NDT and defined POD.
When pushed to the limits of their detection capability, NDE systems do not produce consistent hit/miss
indications. Their capability of detecting small defects is therefore expressed in terms of POD. An adequate
NDE system is required to ensure the structural integrity. In conventional signal response analysis, the POD is
expressed as a function of the defect size, and its adequacy for the inspection task is tested against the maximum
allowable defect size which will not undermine the structural integrity. Analyses of modern structures show that
other parameters, beside the defect size, can both significantly influence the POD and determine the severity of
the defect for the structure. Within the multi-parameter reliability analysis, the POD is expressed as a function of
those influencing parameters. When determining the adequacy of the NDE system, the capability of detecting a
defect has to be expressed and tested against the critical value of exactly that parameter that determines defects
severity for the structure. Failing to do so can lead to a rejection of the healthy, or acceptance of the bad part.
The principle is demonstrated on the example of the Transmit-Receive Longitudinal (TRL) ultrasonic inspection
of the iron cast component for semi-elliptical surface defects.
Within the framework of the European project PICASSO, the radiographic simulator aRTist (analytical
Radiographic Testing inspection simulation tool) developed by BAM has been extended for reliability
assessment of film and digital radiography. A simulation supported probability of detection (POD) methodology
has been developed and the validity of the approach has been studied using an application from the aeronautics
industry. An experimental POD has been determined with the help of a specialized software tool, developed to
aid with the collection of large series of POD data. The resulting POD is compared to simulations of the same
setting using aRTist and the newly available module for simulation supported POD. A quantitative agreement
within a few percent is achieved between the experimental and the simulation supported POD.
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.