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.
