Visual techniques are widely used to ensure product reliability during manufacturing
and to examine any gross discrepancies on the surface of operating components. These
techniques involve illumination of object surface with light and examination of the
reflected light using visual aids, usually at magnification.
Penetrant Inspection
Dye penetrant inspection (DPI), also called liquid penetrant inspection (LPI), is a
widely applied and low-cost inspection method used to locate surface-breaking defects
in all non-porous materials.
Magnetic Particle Inspection
Magnetic particle inspection processes are non-destructive methods for the detection
of surface and sub-surface defects in ferrous materials. They make use of an externally
applied magnetic field or electric current through the material, and the principle that
the magnetic flux will leave the part at the area of the flaw.
Radiography
This technique involves the use of penetrating gamma or X-radiation to examine parts
and products for imperfections. An X-ray machine or radioactive isotope is used as a
source of radiation. Radiation is directed through a part and onto film or other media.
The resulting shadowgraph shows the internal soundness of the part. Possible
imperfections are indicated as density changes in the film in the same manner
as an X-ray shows broken bones.
Ultrasonic Inspection
Ultrasonic inspection can be used for flaw detection/evaluation, dimensional
measurements, material characterization, and more.
Macro Examination
Macro examination is the procedure in which a specimen is etched and evaluated macro
structurally at low magnifications. Macro examination is a frequently used technique
for evaluating steel products such as billets, bars, blooms, and forgings.
