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THE USE OF MAGNETISM IN NDT

After reading this section you will be able to do the following:

  • Explain how magnetism is used in nondestructive testing to find cracks in magnetic materials, such as steel pipes.

Another way magnetism is used, is to inspect material for flaws. 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.

 

That concludes this lesson on magnetism. For more information on magnetism review the material on electricity, if you have not already. As you now know, the two are closely related.

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