NDTnet 1998 Aug, Vol.3 No.8

Full-Text -Abstract

Inspection by non-destructive testing techniques is not perfect and it has become common practice to quantify the reliability of flaw detection in terms of the probability of detection (POD) and the probability of false indication (PM). Experimental measurement of these quantities is expensive and attention has therefore recently turned to modelling them. This paper reviews the current status, benefits, approaches to, and applications of POD modelling. Examples are given of the application of POD models developed by AEA Technology and of current development of specific models within Europe for aerospace application. Methods are discussed for correction of model POD data for human and environmental effects to give POD predictions comparable with those obtained in experimental trials.

A number of computer models are now available, increasingly used and validated for prediction of POD and PFI. These cover an increasing range of inspection techniques and run in real time on standard PCs. Methods are evolving to correct model predictions for human error. The model approach provides complementary data to experimental assessments and allows existing experimental data to be more widely used. POD models can provide specific data not available from experimental measurements such as: (i) parametric studies, (ii) assessment of historical data and (iii) optimisation at the design stage. Current applications include economic assessment, integrity assessment, validation of inspection procedures and plans, and to support safety cases. The values of POD now being obtained by modelling are not dissimilar in accuracy to those obtained in experimental trials.

POD models should be seriously considered as an integral part of future POD trials. This could reduce the number of test samples required, help gain acceptance and familiarity with model use, provide validation and lead to improvements in the model predictions and correction methods used for human error. Use of such models is likely to significantly infuture years. There is a need fordevelopment ofcustomisedmodels for specific applicationsand industries,increasedvalidation as use increases, andmore work on human andenvironmental effects. Supportfrom industry to meet theseobjectives is sought.

Fig. The basis of a model for POD, with simulated radiographic image.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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