Magnetic Inspection OR Magnetic Particle Test
Magnetic test is used for detecting surface defects of ferrous magnetic materials and alloys. The component under test is magnetized applied DC directly to the test piece through a coil, surrounding the specimen. The magnetic powder like iron is applying to the surface dry or wet in a suspension of water light oil.
If the surface of the component behaves in the same way as the gap between the south-north poles of two magnets the lines of force flow across the crack and destruction can be found out at the crack region.
The magnetic method is very rapid identification of defect and is very easy. The defects which are perpendicular to the line of force are efficiently detected. But the flaws (defect) that lie along the lines of force may not detect. The test is suitable only for magnetic material.
Magnetic flux field in magnetized bars having Surface and subsurface discontinuities.
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