The Use of Magnetism in NDT/NDE

Magnetism is used in nondestructive testing and evaluation to find flaws in magnetic materials such as iron. You may recall from the introduction that nondestructive testing (NDT) is the use of special equipment and methods to learn something about an object without harming the object. One of the NDT methods commonly used is called magnetic particle inspection. The reason we use this test is to find small defects in objects before they become bigger defects and cause serious problems.

In magnetic particle inspection, a magnet or electrical current is used to establish a magnetic field in the object. Iron filings are then dusted on to the surface of the object. The filings should align along the magnetic lines of force. If a crack or other defect is present, the magnetic fines of force will be disrupted and the magnetic particles will cluster along the edges of the flaw.