Magnetic particle inspection is widely used to inspect production parts, parts in service and for periodic inspection of structures such as bridges, aircraft engines and landing gear. The method was originally developed in the late 1920s and through the years has been improved to speed up the inspection of production parts and to increase test method sensitivity.
This method always consists of two things: the application of a magnetizing force along with an indicating medium. How the force is applied and the type of indicating medium that is used varies, but the basic physics is always the same.