| Penetrant
solution is applied to the surface of a precleaned component.
The liquid is pulled into surface-breaking defects by capillary
action. Excess penetrant material is carefully cleaned from
the surface. A developer is applied to pull the trapped
penetrant back to the surface where it is spread out and
forms an indication. The indication is much easier to see
than the actual defect. |
A
magnetic field is established in a component made from ferromagnetic
material. The magnetic lines of force travel through the
material, and exit and reenter the material at the poles.
Defects such as crack or voids cannot support as much flux,
and force some of the flux outside of the part. Magnetic
particles distributed over the component will be attracted
to areas of flux leakage and produce a visible indication. |
High
frequency sound waves are sent into a material by use of
a transducer. The sound waves travel through the material
and are received by the same transducer or a second transducer.
The amount of energy transmitted or received and the time
the energy is received are analyzed to determine the presence
of flaws. Changes in material thickness, and changes in
material properties can also be measured. |
Alternating
electrical current is passed through a coil producing a
magnetic field. When the coil is placed near a conductive
material, the changing magnetic field induces current flow
in the material. These currents travel in closed loops and
are called eddy currents. Eddy currents produce their own
magnetic field that can be measured and used to find flaws
and characterize conductivity, permeability, and dimensional
features. |
X-rays
are used to produce images of objects using film or other
detector that is sensitive to radiation. The test object
is placed between the radiation source and detector. The
thickness and the density of the material that X-rays must
penetrate affects the amount of radiation reaching the detector.
This variation in radiation produces an image on the detector
that often shows internal features of the test object. |
| Used
to locate cracks, porosity, and other defects that break
the surface of a material and have enough volume to trap
and hold the penetrant material. Liquid penetrant testing
is used to inspect large areas very efficiently and will
work on most nonporous materials. |
Used
to inspect ferromagnetic materials (those that can be magnetized)
for defects that result in a transition in the magnetic
permeability of a material. Magnetic particle inspection
can detect surface and near surface defects. |
Used
to locate surface and subsurface defects in many materials
including metals, plastics, and wood. Ultrasonic inspection
is also used to measure the thickness of materials and otherwise
characterize properties of material based on sound velocity
and attenuation measurements. |
Used
to detect surface and near-surface flaws in conductive materials,
such as the metals. Eddy current inspection is also used
to sort materials based on electrical conductivity and magnetic
permeability, and measures the thickness of thin sheets
of metal and nonconductive coatings such as paint. |
Used
to inspect almost any material for surface and subsurface
defects. X-rays can also be used to locates and measures
internal features, confirm the location of hidden parts
in an assembly, and to measure thickness of materials. |
|
Large surface areas or large volumes
of parts/materials can be inspected rapidly and at low
cost.
Parts with complex geometry are routinely
inspected.
Indications are produced directly on
surface of the part providing a visual image of the discontinuity.
Equipment investment is minimal.
|
Large surface areas of complex parts
can be inspected rapidly.
Can detect surface and subsurface flaws.
Surface preparation is less critical
than it is in penetrant inspection.
Magnetic particle indications are produced
directly on the surface of the part and form an image
of the discontinuity.
Equipment costs are relatively low.
|
Depth of penetration for flaw detection
or measurement is superior to other methods.
Only single sided access is required.
Provides distance
information.
Minimum part preparation is required.
Method can be used for much more than
just flaw detection.
|
Detects surface and near surface defects.
Test probe does not need to contact
the part.
Method can be used for more than flaw
detection.
Minimum part preparation is required.
|
Can be used to inspect virtually all
materials.
Detects surface and subsurface defects.
Ability to inspect complex shapes and
multi-layered structures without disassembly.
Minimum part preparation is required.
|
|
Detects only surface breaking defects.
Surface preparation is critical as contaminants
can mask defects.
Requires a relatively smooth and nonporous
surface.
Post cleaning is necessary to remove
chemicals.
Requires multiple operations under controlled
conditions.
Chemical handling precautions are necessary
(toxicity, fire, waste).
|
Only ferromagnetic materials can be inspected.
Proper alignment of magnetic field and
defect is critical.
Large currents are needed for very large
parts.
Requires relatively smooth surface.
Paint or other nonmagnetic coverings
adversely affect sensitivity.
Demagnetization and post cleaning is
usually necessary.
|
Surface must be accessible to probe and
couplant.
Skill and training required is more extensive
than other technique.
Surface finish and roughness can interfere
with inspection.
Thin parts may be difficult to inspect.
Linear defects oriented parallel to the
sound beam can go undetected.
Reference standards are often needed.
|
Only conductive materials can be inspected.
Ferromagnetic materials require special
treatment to address magnetic permeability.
Depth of penetration is limited.
Flaws that lie parallel to the inspection
probe coil winding direction can go undetected.
Skill and training required is more extensive
than other techniques.
Surface finish and roughness may interfere.
Reference standards are needed for setup.
|
Extensive operator training and skill
required.
Access to both sides of the structure
is usually required.
Orientation of the radiation beam to
non-volumetric defects is critical.
Field inspection of thick section can
be time consuming.
Relatively expensive equipment investment
is required.
Possible radiation hazard for personnel.
|
