NDTnet 1998 April, Vol.3 No.4

Demonstrating the capability of radiography for detection of large planar defects in thick-section welds

A. B. Wooldridge, Magnox Electric, Berkeley (G B); R. K. Chapman, G. S. Woodcock, Nuclear Electric, Gloucester (GB); I.J. Munns, G.A. Georgiou, TWI, Abington Hall, Cambridge (GB)
European-American Workshop Determination of Reliability and Validation Methods of NDE, Berlin - June 18-20, 1997
TABLE OF CONTENTS
Abstract
1. INTRODUCTION
2. EXPERIMENTAL PROCEDURE FOR PHASE I TRIALS
3. SUMMARY OF RADIOGRAPHIC RESULTS FOR PHASES I AND II
4. DISCUSSION OF RESULTS
5. DEVELOPMENT OF THEORETICAL MODEL FOR RADIOGRAPHY OF REAL METALLURGICAL DEFECTS
6. SUMMARY OF RECENT REVIEW OF DEFECT CHARACTERISTICS
7. DISCUSSION
8. CONCLUSIONS
9. REFERENCES

Abstract

1. INTRODUCTION

2. EXPERIMENTAL PROCEDURE FOR PHASE I TRIALS

3. SUMMARY OF RADIOGRAPHIC RESULTS FOR PHASES I AND II

4. DISCUSSION OF RESULTS

5. DEVELOPMENT OF THEORETICAL MODEL FOR RADIOGRAPHY OF REAL METALLURGICAL DEFECTS

6. SUMMARY OF RECENT REVIEW OF DEFECT CHARACTERISTICS

7. DISCUSSION

8. CONCLUSIONS

  1. The detectability of a given size of defect is sensitive to the metallurgical mechanism which created the defect. The mechanism can affect both the orientation (tilt) and the separation of the faces of the defect (gape), which both have a critical effect on detectability.

  2. The Pollitt model for the radiographic inspection of smooth parallel-sided slots provides useful predictions of the dependencies of detectability on such defect parameters as orientation, gape and through-wall extent. However, it cannot be expected to accurately model real rough defects of variable gape.

  3. The more general theoretical model being developed by BAM offers a promising way of predicting the radiographic images of such more complex defects.

  4. Experimental studies of radiographic capability need to be specific about the metallurgical types of defects being addressed, and the morphologies of any defects studied should be compared with those of natural defects.

  5. For the range of manufacturing defects studied in the IMC-funded programme (lack-of-sidewall fusion, solidification and hydrogen cracking), all of those which were extensive in length and in through-wall extent were detected radiographically for all exposures performed.

  6. All the solidification cracks and lack of fusion defects studied which exceeded 4 mm in through-wall extent were detected radiographically for all exposures performed; some were at misorientations of up to 40°.

  7. Those hydrogen cracks studied which were extensive in length and depth were detectable up to 40°, whereas the shorter, mainly transverse, cracks were much harder to detect. Sectioning revealed that most of the cracks which were hard to detect had very tight gapes. It is not yet possible to tell whether such gapes were due to the method of producing the cracks, the parent materials used, the restricted length of the defects, or a combination of all factors.

  8. The defect through-wall extent did not have a major influence on detectability, at least for defects exceeding about 10 mm through-wall extent. Theoretical modelling predictions confirm this effect.

    9. REFERENCES

    10. ACKNOWLEDGEMENTS |Top|
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    Copyright © Rolf Diederichs, rd@ndt.net 1. Apr 1998
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