Radiography of thin-section welds, Part 4: Further modelling
This paper describes the further refinement of a simple model of radiography, first published by Pollitt in 1962, which treats flaws as smooth, parallel-sided slots. It builds on the work on thin-section welds presented at NDT'02, and earlier work by TWI on thicker welds.
The latest experimental data were collected from 13 realistic planar flaws in welds of thicknesses 10–50 mm. They were radiographed under various exposure conditions, giving 284 flaw/radiograph combinations (supplementing 333 flaw/radiograph combinations already available from earlier work on thicker welds). Each radiograph was evaluated ‘blind’ by two radiographers. The specimens were then sectioned to determine defect size, orientation and gape. A separate paper at this conference (Part 3) describes the practical aspects of the work.
The experimental data show variations in detectability that are strongly correlated with theoretical predictions. The broader range of the available experimental data has enabled us to improve the accuracy of our previously published statistical models for the reliability of radiography. Different models are proposed in the cases of:
The latest experimental data were collected from 13 realistic planar flaws in welds of thicknesses 10–50 mm. They were radiographed under various exposure conditions, giving 284 flaw/radiograph combinations (supplementing 333 flaw/radiograph combinations already available from earlier work on thicker welds). Each radiograph was evaluated ‘blind’ by two radiographers. The specimens were then sectioned to determine defect size, orientation and gape. A separate paper at this conference (Part 3) describes the practical aspects of the work.
The experimental data show variations in detectability that are strongly correlated with theoretical predictions. The broader range of the available experimental data has enabled us to improve the accuracy of our previously published statistical models for the reliability of radiography. Different models are proposed in the cases of:
large planar flaws (≥15 mm in through-wall extent) in thick-section welds,
small planar flaws (<8 mm through-wall) in thin-section welds, and
small flaws of complex morphology in thin-section welds.
Document Type: Research Article
Affiliations: 1: TWI, Cambridge CB1 6AL, UK 2: Jacobi Consulting Ltd, London N1 3NL, UK
Publication date: 01 February 2005
- Official Journal of The British Institute of Non-Destructive Testing - includes original research and development papers, technical and scientific reviews and case studies in the fields of NDT and CM.
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