The intention of this paper has been to describe a conventional statistical test which has a practical application in preparing for testing a pipeline with AUT. It does not remove the need for good judgement in deciding whether the data is appropriate for such analysis, for example whether the distributions of data are really normal, or whether there are points which need to be removed and treated separately, as is the case for stacked defects. Good knowledge of statistical methods is highly desirable in such decisions. The graphs of the results presented shows that AUT data can be very widely spread. This is, of course, the case with all amplitude based ultrasonic methods. It is why the time-of-flight diffraction (ToFD) method was originally developed and it should always be used as the first preference where it can be. All the systems used in this study also used ToFD probes, so it is clear that ToFD will not always resolve even large flaws to give accurate height measures. Statistical methods are increasingly used in the analysis of AUT data and should be founded on a good understanding of their application and limitations. Nonetheless, the t-test, in particular, can allow a small number of tests to be used to corroborate (or otherwise) the validity of using previous data for a new project. Its use has been illustrated with sets of test data. Actual project work has demonstrated that it can be used without difficulty by contracting companies. It is hoped that greater use of statistical methods will be made on future pipeline projects.
Automated ultrasonic testing (AUT). Qualifications and variations
Automatische Ultraschallprüfung (AUT). Qualifikationen und Variationen
Insight ; 51 , 5 ; 266-270
2009
5 Seiten, 9 Bilder, 14 Quellen
Article (Journal)
English
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