History of Magnetic Particle
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, if cannon barrels were magnetized and then a magnetic compass were passed over the barrel, iron components could be detected.
At this time particles were not used but the principle of seeking leakage fields was. It wasn't 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.
What is Magnetic Particle Testing?
Magnetic Particle Testing electrically induces magnetic fields in ferrous material to create a highly sensitive inspection method. This procedure is applicable to all sizes and shapes of both weld and base materials for forgings, pipe and tubing, castings or other shapes and can be used for all ferromagnetic materials.
This method can detect minuscule cracks and slightly subsurface discontinuities that can lead to part fatigue and eventually part failure.