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Probability of detection of surface defects in metals using optical inspection techniques

Auffindwahrscheinlichkeit von Oberflächenfehlern in Metallen mittels optischer Inspektionsverfahren
: Rauhut, M.; Spies, M.; Taeubner, K.

Thompson, D.O. ; American Institute of Physics -AIP-, New York:
Review of progress in quantitative nondestructive evaluation : San Diego, California, 18-23 July 2010, Volume 30A, Volume 30B
New York, N.Y.: AIP Press, 2011 (AIP Conference Proceedings 1335)
ISBN: 978-0-7354-0888-3
ISSN: 0094-243X
Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE) <37, 2010, San Diego/Calif.>
Conference Paper
Fraunhofer ITWM ()
probability of detection; optical inspection; metal; algorithm; validation

The quality of industrial products is in many cases directly linked to the quality of their surfaces. For products such as metallic seals or aero engine blades the integrity of the surfaces has to be checked in order to ensure the intended performance of the respective component. Aside from the classical NDE techniques for surface inspection optical methods gain increasing importance, especially in view of automated quality control procedures. Optical inspection systems operate without contact and offer various possibilities for online defect detection and classification. Depending on the quality of the lighting and (video) camera system different resolutions with respect to the detectable defect size can be achieved. In order to quantitatively evaluate different systems used for on-site i nspections, we have performed an â versus a-analysis to determine the Probability of Detection (POD) for planar specimens with boreholes and notches of different dimensions and orientations. Following the international standard according to MIL-HDBK-1823 in the 2007 update version we have determined POD-curves using the digitized and algorithmically processed data. We show that the application of more complex sensor technology and algorithms correspondingly leads to improvement of the POD. This supports the use of optical surface inspection techniques for quantitative NDE in the field of automated quality control of e.g. stampings or in production lines of steel sheets. Further valuable aspects are the objectiveness in view of quality criteria and the reduction of the human factor.