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Magnetic
Particle Inspection: The "3D" Approach |
| Consider the inspection of a ring-shaped part.
As shown in the figures below, such parts can have circumferential defects
(on the left) or axial/radial defects (on the right). |
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Circumferential defects can be detected by setting up a toroidal field,
a single line of which is shown as blue arrows in the picture on the left
below. The toroidal field basically encircles the ring at every position
along the ring's circumference. It allows for detection of circumferential
defects to be detected on all faces of the ring. Using the central
conductor approach, a circular field (below, right) can be established
for the detection of any axial/radial flaws.
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| A toroidal field can be set up in a ring-shaped
part by placing the ring in a coil with their axes parallel.Alternating
current through the coil induces a circular electrical current in the part
which, in turn, produces the toroidal magnetic field. An iron core can be
placed along the common axis to enhance the field. The S-5000 "3D"
approach is to use the field flow magnetization method to establish a strong
axial magnetic field. As this field alternates its direction, a circular
current is again produced in the ring resulting in a toroidal field.(The
ring is laying flat and is clamped between both head stocks.) The field
produced in this case tends to be stronger and more effective for flaw detection
than one produced with a coil. Thus, with the S-5000 in "3D" mode,
a ring-shaped part could be inspected with a single shot, depending on the
fill factor of the part. |
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