Inspections
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Magnetic
Particle (MT) Examination
A nondestructive test method used to detect discontinuities at
or near the surface of ferromagnetic materials. The principle of
the examination consists of magnetizing an article and applying
magnetic particles to the magnetized surface of the test article,
then the test surface is examined for any accumulation of particles
(indications) at points causing magnetic field leakage caused by
discontinuities and the indications are evaluated to an acceptance
standard.
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Eddy
Current (ET) Examination
Eddy Current testing is a nondestructive test which compares the
condition of a test to that of a reference standard of sound material
with known defects. When the test coil is placed next to an electrically
conductive part, the primary magnetic field causes eddy currents
to flow in the part (Faraday's law). This flow of eddy currents induced
in a material generates a second magnetic field in the part called
a secondary field. If there is an interruption in the field, such
as a flaw, then the change in the current flow is represented on
the instrument’s screen in a presentation similar to the test
standard.
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Liquid
Penetrant (PT) Examination
A nondestructive test method used to detect discontinuities open
to the surface. The principle of the test consists of applying penetrant
to the surface being examined then allowing it sufficient time to
enter the discontinuities by capillary action. The excess penetrant
is then removed from the surface in such a manner as to leave the
penetrant in the discontinuity cavities undisturbed. A developer
is applied. The developer acts as an absorbent blotter to draw the
penetrant out of the discontinuity cavity. The bleeding penetrant
back to the surface into the developer causes an indication in the
form of a penetrant stain in the developer coating. The amount and
type of indication bleed-out is then interpreted and evaluated to
the appropriate acceptance criteria.
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Ultrasonic
(UT) Examination
A series of electrical pulses is applied to a transducer which converts
these pulses to mechanical energy in the form of pulsed waves at
a selected nominal frequency. The transducer transmits the waves
into the material through the surface of the part and couplant. Pulsed
energy is transmitted into the material and is reflected back to
the search unit by a discontinuity or boundary which is parallel
or near parallel to the contacted surface. By comparison of the displayed
signal amplitudes to those from a reference standard, both location
and estimated discontinuity size may be determined.
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Radiography
The X-ray technique is a non-destructive method of detecting surface
and subsurface defects in a part or assembly. X-rays are produced
when electrons traveling at a high speed in a vacuum are stopped
by matter. Some of the radiation will be absorbed and scattered
as it passes through the part. When the beam of penetrating radiation
is directed through the part then the amount of radiation passing
through the part is observed or recorded on a photographic type
film called X-ray film. After the film is processed, a shadow
picture of the internal structure of the part is obtained. This
technique is used to inspect castings, welds, wrought structures,
adhesive bonds / composites, aircraft structure and instruments.
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