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Field direction for flaw detection :
For maximum detection sensitivity the magnetic field should be 90 Degree to the major dimension of the flaw. However magnetic field direction up to 45 Degree to the major dimension may produce detectable indications.
The required magnetic field can be introduced into a component in a number of different ways.
1.Using a permanent magnet or an electromagnet that contacts the test piece
2.Flowing an electrical current through the specimen
3.Flowing an electrical current through a coil of wire around the part or through a central conductor running near the part.
1. A suitable technique of magnetization is chosen.
2. The part is magnetized in the desired direction.
3. While the magnetizing field is present, iron powders
are applied dry or wet.
4. Iron powders bridge the leakage fields, if present, to produce
indications.
5. Powder patterns produced by flaws are identified and
accept reject decision is made.
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