The history and basis of the magnetic particle testing method

Abstract

Possibly the earliest reference to magnetic testing of iron comes from an article by S.H. Saxby in volume 5 of the journal Engineering in 1868. Saxby reported that defects in cannon barrels and other iron components could be detected if they were magnetized and then a magnetic compass were passed over them. No particles were used but the principle of seeking leakage fields was used. It was not until the 1920s that the use of magnetic particles for detection and other magnetic discontinuities in magnetized iron and steel was recognized. W.E. Hoke, working in the American Bureau of Standards, had noticed patterns of metal grindings on steel parts which were being worked upon while held on a magnetic chuck. On investigating these patterns more closely Hoke discovered that they coincided with patterns of defects in the surface. In the following 20 years, the foundations of the magnetic particle inspection method of non-destructive testing were laid down. Many people on both sides of the Atlantic Ocean contributed to these firm foundations on which the modern application of the method is built.