Eddy-Current Testing of Thin Nonferromagnetic Plate and Sheet Materials Using a Facsimile-Recording Data Display Method
SourceThe wide-spread use of eddy-current testing of thin flat plates or sheet materials has been hampered by the difficulty of test signal interpretation and the problem of locating the discontinuity when the test has been completed. These drawbacks could be reduced by a simple facsimile-recording system that displays the test-signal amplitude changes as changes in the darkness of the facsimile recording. The interpretation of the facsimile recording is very similar to the interpretation of standard radiographic films or ultrasonic C-scan data. The location of the discontinuity on the specimen is directly related to the discontinuity indication on the facsimile recording, again analogous both to radiography and ultrasonic C-scan. This technique of data presentation also allows for the differentiation between discontinuities that extend through the full thickness of the specimen and the discontinuities that extend only partially through the full thickness. Small-diameter discontinuities can be also detected and displayed by this system.