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Quantitative NDE - New technologies for detection classification and sizing of defects in combination with probabilistic FAD-approaches

 
: Dobmann, G.; Bulavinov, A.; Kröning, M.; Kurz, J.H.

:
Fulltext urn:nbn:de:0011-n-619974 (688 KByte PDF)
MD5 Fingerprint: d294848711df9f65cc8e33b275c2c09e
Created on: 30.08.2007


Gupta, A. ; International Association for Structural Mechanics in Reactor Technology -IASMIRT-:
19th International Conference on Structural Mechanics in Reactor Technology, SMIRT 19. Proceedings : August 12-17, 2007, Toronto, Canada
Toronto: Omnipress, 2007
Paper O-02/1, 8 pp.
International Conference on Structural Mechanics in Reactor Technology (SMIRT) <19, 2007, Toronto>
English
Conference Paper, Electronic Publication
Fraunhofer IZFP ()
sampling phased array; synthetic aperture focusing technique (SAFT); failure assessment diagram (FAD)

Abstract
Starting with the damage tolerance design of structures in aerospace applications [1] it became obvious: NDT procedures, utilized according to standards in the regulated area and according to technical reports, guidelines and handbooks in non-regulated applications have to take into account the uncertainties of the techniques. These are system features influenced by the type of product to be inspected, more over its individual design and manufacturing techniques, the type of non-conformity or irregularity to be detected, the type of ND technique selected, the hardware (transducer and system electronics), the software reliability and - the human factor influence of the inspector. All of the influences are summarized in a feature which is called POD - probability of detection. If there is a certain probability of detection, then there is also a PND, a probability for non-detection. As each technical system is not complete and not ideal the indication of a "'finding" or an "alarm" by the system can be a real hit but also a false indication, or also called, false alarm. In the same way, in the case of a "calm"system, i.e. no alarm is observed and no finding is indicated, the system' answer can be true or false. For each of the four cases the knowledge of the probability has to be known. So far as a probabilistic approach is applied [2] POD distributions as function of the size of an individual material irregularity are relevant influencing parameters concerning the probability of the failure of a component evaluated according to a failure assessment diagram (FAD). The contribution introduces into the state of the art of a software development which will be applied to evaluate components integrity after performing in-service inspections. Special emphasis is on the description of the state of the art concerning a NDT-technology newly developed. The flexible "Sampling Phased Array Technique" [3] combines a high speed hardware approach with an interpretation software which online also analyze complex structures like austenitic and/or dissimilar-multi-layer-metal-welds and allows the representation of defects at its original position, even if complex, anisotropic microstructure is disturbing the inspection task. Procedures like SAFT (Synthetic Aperture Focusing Technique) are integrated. They allow the refocusing of the inspection data sensed in an inspection aperture into a pixel space for imaging. The image allows visualizing defects in order to predict the size. Whereas conventional ISI-procedures are based on fixed angular probe UT, Phased Array probes allow a flexible multiple-angle-inspection. This procedure is optimal when - as in the case of sampling phased array - by fast computing each position in 3D-space can be allocated with a focus spot.

: http://publica.fraunhofer.de/documents/N-61997.html