INTRODUCTION & BASIC PRINCIPLE
When magnetism applied through ferromagnetic materials by using electrically or by using permanent magnet, magnetic poles of leakage field will occur at discontinuities. Magnetic powders applied throughout the object to see such leakage field as discontinuity indication.
APPLICATION
Magnetic particle testing is a relatively simple test method that can be applied to finished articles, billets, hot rolled bars, castings, and forgings. It can also be used to check that the processing operations such as heat treat, machining, and grinding did not uncover or cause discontinuities. Magnetic particle consists of magnetization of the article, application of the particles, and interpretation of the patterns formed by the particles as they are attracted by magnetic leakage fields.
ADVANTAGES
Magnetic Particle Testing is one of most economical method to find out surface cracks in ferromagnetic materials. It is portable and easy for application.
LIMITATION
It is limited application to only on ferromagnetic materials. Further it is limited to disclosing only those discontinues that are at or near the surface.