ASME PCC-2–2018
Table 502-I-1 Comparison of Selected NDE Methods
Method
Properties Sensed or
Measured
Typical
Discontinuities
Detected
Representative
Applications
Advantages
Limitations
X- and gamma-ray
radiography
Changes in density
Voids, porosity,
from voids,
inclusions,
inclusions, material
incomplete
variations, and
penetration, and
placement of
cracks
internal parts
Castings, forgings,
weldments, and
assemblies
Liquid penetrant
examination
Surface openings
Cracks, porosity,
laps, and seams
Castings, forgings,
Inexpensive; easy to
weldments, metallic apply; portable
and nonmetallic
components
Eddy current
examination
Changes in electrical
and magnetic
properties caused
by surface and
near-surface
discontinuities
Cracks, laps, seams,
Bars, rods, wire,
voids, and variations tubing, local
in alloy composition regions of sheet
and heat treatment
metal, alloy
sorting, and
thickness gaging
Microwave
examination
Anomalies in
In dielectrics;
complex dielectric
disbands voids,
coefficient; surface
and cracks;
anomalies in
in metal surfaces;
conductive
surface cracks
materials
Glass-fiber-resin
Noncontacting; readily No penetration of
structures; plastics;
automated; rapid
metals;
ceramics; moisture
inspection
comparatively poor
content; thickness
definition of flaws
measurement
Magnetic particle
examination
Leakage in magnetic
flux field caused
by surface or
near-surface
discontinuities
Surface or nearsurface cracks,
laps, voids, and
nonmetallic
inclusions
Ferromagnetic
Stable; inexpensive
products such as
weldments, castings,
forgings, and
extrusions, and
other basic steel
products
Magnetic flux
Leakage in magnetic
leakage examination flux caused by
surface or nearsurface
discontinuities
Surface or nearsurface cracks,
laps, voids, and
nonmetallic
inclusions
Ferromagnetic
Sensitivity to typical Ferromagnetic
products such as
discontinuities;
materials only;
weldments, castings, readily automated;
proper
forgings, and
moderate depth
magnetization of
extrusions, and
penetration;
part sometimes
other basic steel
permanent record, if difficult when parts
products
needed
do not have uniform
cross sections
Ultrasonic
examination
Changes in acoustic
impedance
Cracks, voids,
porosity,
lamination,
delaminations
and inclusions
Weldments, plates,
Excellent penetration; Requires acoustic
tubes, castings,
readily automated;
coupling to surface;
forgings, extrusions; good sensitivity and reference standard
thickness gaging
good resolution;
required; highly
requires access to
dependent upon
only one side,
operator skill;
permanent record, if relative insensitivity
needed
to laminar flaws
which are parallel to
the sound beam
Sonic examination
Changes in acoustic
impedance
Disbands,
delaminations,
cracks, or voids
Laminated structures; Simple to implement; Geometry sensitive;
honeycomb; small
readily automated;
poor definition
parts
portable
Ultrasonic
holography
Same as ultrasonic
examination
Used primarily for
evaluation of
discontinuities
detected by other
methods
Examination of a
Produces a viewable
limited region of the image of
structure in each
discontinuities
image
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Detects internal
Cost; relative
discontinuities;
insensitivity to thin
useful on a wide
or laminar flaws
variety of materials; such as fatigue
portable; permanent cracks or
record
delaminations that
are perpendicular to
the radiation beam;
health hazard
Discontinuity must be
open to an accessible
surface; false
indication often
occurs
Moderate cost; readily Conductive materials
automated;
only; shallow
portable; permanent penetration;
record, if needed
geometry sensitive;
reference standards
necessary
Ferromagnetic
materials only;
surface preparation
may be required;
false indications
often occur
Cost; limited to small
regions of the
structure; poor
definition compared
to radiography
ASME PCC-2–2018
Table 502-I-1 Comparison of Selected NDE Methods (Cont’d)
Method
Properties Sensed or
Measured
Typical
Discontinuities
Detected
Representative
Applications
Advantages
Limitations
Infrared testing
Surface temperature; Voids or disbands in
anomalies in
nonmetallics;
thermal
location of hot or
conductivity or
cold spots in
surface emissivity,
thermally active
or both
assemblies
Laminated structures; Produces a viewable
honeycomb; electric thermal map
and electronic
circuits; insulated
structures;
refractory-lined
structures and
machinery
Cost; difficult to
control surface
emissivity; poor
definition
Strain gages
Mechanical strains
Not used for
detection of
discontinuities
Stress–strain analysis Low cost; reliable
of most materials
Insensitive to
preexisting strains;
small area coverage;
requires bonding to
surface
Brittle coatings
Mechanical strains
Not commonly used
for detection of
discontinuities
Stress–strain analysis Low cost; produces
of most materials
large area map of
strain field
Insensitive to
preexisting strains
Optical holography
Mechanical strains
Disbands;
Honeycomb;
Extremely sensitive, Cost; complexity;
delaminations;
composite structure; produces a map of
requires
plastic deformation
tires; precision parts strain field;
considerable skill
such as bearing
permanent record, if
elements
needed
Acoustic emission
Stress wave energy
Cracks, structural
Crack detection and 100% volumetric
Structure must be
generated by
anomalies, leaks,
location during
examination in real
loaded, to a higher
growing flaws, areas also delamination,
proof testing crack
time, complicated
level than previous
of high stress, leaks
fiber fracture, and
propagation,
geometries, very
service loadings,
matrix failure in
composite,
high sensitivity,
sensors must be in
composite materials structures, metal
permanent record,
contact with
structures, rotating
accurate flaw
structure
equipment
location
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