NDT
Glossary
>>
A
B C
D E
F G
H I
J K
L M
N O
P Q
R S
T U
V W
X Y
Z
S
- Safelight
- A special lamp used in the darkroom to provide working visibility without
affecting the photosensitive emulsion of the radiographic film.
- Samarium
145 - A radioisotope of the element samarium.
- Saturation
(Magnetic) - A condition where incremental magnetic permeability
of a ferromagnetic material becomes 1.0.
- Saturation
Level - The limit of indication height that is obtained as the area
of the discontinuity is increased.
- Scanning
- Movement of the transducer over the surface of the test object in a
controlled manner so as to achieve complete coverage. May be either contract
or immersion method.
- Eddy current
data can be collected using automated scanning systems to improve the quality
of the measurements and to construct images of scanned areas.
- Scattering
- Random reflection of ultrasonic waves by small discontinuities or surface
irregularities.
- Scattering
Ultrasonic
- Dispersion of ultrasonic waves in a medium due to causes other than absorption.
- Schlieren
System
- An optical system used for visual display of an ultrasonic beam passing
through a transparent medium.
- Scintillation
Counter - A device for counting atomic particles by means of tiny
flashes of light (scintillations) which the particles produce when they strike
certain crystals.
- Search
Unit - An assembly comprising a piezoelectric element, backing material
(damping), wear plate or wedge (optional) and leads enclosed in a housing.
Also called transducer or probe.
- Secondary
Field - The magnetic field produced by induced eddy currents.
- Secondary
Radiation
- Particles or rays produced by the interaction of any type of primary radiation
with matter, e.g. Compton recoil electrons.
- Seeability
- The characteristic of an indication that enables an observer to see it against
the adverse conditions of background, outside light, etc.
- Segregation
- Nonuniform distribution of alloying elements, impurities or microphases.
- Segregation
Radiographic
- Variation in film density which can be explained by segregation of elements
of atomic numbers different from that of the matrix.
- Self-Emulsifiable
- The property of a liquid penetrant to combine satisfactorily with water,
in either emulsion or solution form, to permit its being removed from a surface
by washing (rinsing) in water. Synonymous with water-washable.
- Self-Inductance
- The property of an electric circuit or component
that caused an e.m.f. to be generated in it as a result of a change in the
current flowing through the circuit.
- Semi-Infinite
Conductor - A crystalline solid, such as silicon
or germanium, with an electrical conductivity intermediate between that of
a conductor and an insulator.
- Send-Receive
- The variations in the test object which affect current flow within the test
object can be detected by observing their effect upon the voltage developed
across a secondary receive coil.
- Send/
Receive Transducer
- A transducer consisting of two piezoelectric elements mounted side by side
separated by an acoustic barrier. One element transmits, one receives.
- Sensitivity
- A measure of the ability to detect small signals. Limited by the signal-to-noise
ratio.
- Sensitivity
Panel - A plated metal panel with cracks of know depth induced into
the plating; used to evaluate and compare penetrant sensitivity.
- Sensitometric
- The process or technique of producing images of
an opaque object on photographic film or on a fluorescent screen by means
of radiation.
- Series Circuit
- A circuit that has only one path for the electrons to take.
- Shadow
- A region in a test object that cannot be reached by ultrasonic energy traveling
in a given direction. Shadows are caused by geometry or the presence of intervening
large discontinuities.
- Shallow
Discontinuity
- A discontinuity open to the surface of a solid object which possesses little
depth in proportion to the width of this opening. A scratch or nick may be
a "shallow discontinuity" in this sense.
- Shear
- A type of force that causes or tends to cause two regions of the same part
or assembly to slide relative to each other in a direction parallel to their
plane of contact. May be considered on a microscale when planes of atoms slide
across each other during permanent, or plastic, deformation. May also be considered
on a macroscale when gross movement occurs along one or more planes, as when
a metal is cut or sheared by another metal.
- Shear
Fracture
- Fracture that occurs when shear stresses exceed shear fractures are transverse
fracture of a ductile metal under a torsional (twisting) stress, and fracture
of a rivet cut by sliding movement of the joined parts in opposite directions,
like the action of a the pair of scissors.
- Shear
Horizontal Wave
- A shear wave in which the particle vibration is parallel to the incidence
surface. Abbreviated SH wave.
- Shear
Lip - A narrow, slanting ridge, nominally about 45° to the surface,
along the edge of a fracture of a ductile tensile specimen, the shear lip
forms the typical “cup-and-cone” fractures. Shear lips may be
present on the edges of some predominantly brittle fractures to form a “picture
frame” around the surface of a rectangular part.
- Shear
Vertical Wave - A shear wave in which the plane of vibration is normal
to the incidence surface. Abbreviated SV wave.
- Shear Waves
- Waves
which move perpendicular to the direction the wave propagates.
- Shear
Wave Transducer
- An angle beam transducer designed to cause converted shear waves to propagate
at a nominal angle in a specified test medium.
- Shielding
- A barrier surrounding a region to exclude it from
the influence of an energy field.
- Shoe
- A device used to adapt a straight beam transducer for use in a specific
type of testing, including angle beam or surface wave tests and tests on curved
surfaces. See also wedge.
- Shot
Peening - A carefully controlled process of blasting a large number
of hardened spherical or nearly spherical particles (shot) against the softer
surface of a part. Each impingement of a shot makes a small indentation in
the surface of the part, thereby inducing compressive residual stresses, which
are usually intended to resist fatigue fracture or stress-corrosion cracking.
- Shrink
- Internal rupture occurring in castings due to contraction during cooling.
Also applied to surface shrinkage cracks.
- Shrinkage
Cavity - Cavities in castings caused by lack of sufficient molten
metal as the casting cools.
A small bubble in metal that appears as dendritic, filamentary, or jagged
darkened area on a radiograph film.
- Shrinkage
Cracks - Hot tears associated wit shrinkage cavities.
- Shrinkage
Porosity or Sponge - A localized lacy, or honeycombed, darkened area
on a film that indicates porous metal.
- SH Wave
- See shear horizontal wave.
- Signal
- A change in eddy current instrument output voltage; It has amplitude and
phase.
- Signal-to-Noise
Ratio -
Ratio between defect signal amplitude and that from non-relevant indications.
Minimum acceptable ratio is 3:1.
- Silver
- A
discontinuity consisting of a very thin elongated piece of metal attached
by only one end to the parent metal into whose surface it has been rolled.
- Single-Phase
Alternating Current
- Simple current, alternating in direction. Commercial single-phase current
follows a sine wave. Such a current requires only two conductors for its circuit.
Most common commercial Frequencies are 25, 50 and 60 cycles per second.
- Skin
Depth - See depth of penetration.
- Skin
Effect - A phenomenon where induced eddy currents are restricted
to the surface of a test sample. Increasing test frequency reduces penetration.
- Skip
Distance - In angle beam tests of plate or pipe, the distance from
the sound entry point to the first reflection point on the same surface. See
V-path.
- Slag
Inclusions - Nonmetallic solid material entrapped in weld metal or
between weld metal and base metal.
- Snell’s
Law - The physical law that defines the relationship between the angle
of incidence and the angle of refraction.
- Soak
Time - The period time wherein the emulsifier remains in contact
with the liquid penetrant/emulsifier is quenched with water, or completely
removed by water rinsing. Synonymous with emulsification time.
- Soft
X-Rays - The quality or penetrating power of x-radiation; their penetrating
power is relatively slight.
- Solenoid
- An
electrically charged coil of insulated wire which produces a magnetic field
within the coil.
- Solidification
Shrinkage - The decrease in volume of a metal during solidification.
- Solvent
Action - The dissolution of a fluid or solid by another material.
- Solvent
Cleaning
- The process of removing the excess penetrant from the surface of a part
by washing or wiping with a solvent for the penetrant.
- Solvent
Developer
- A developer in which the developing powder is applied as a suspension in
a quick-drying solvent.
- Solvent
Remover - A nonaqueous liquid employed in removal of surface penetrant
from parts or for removal of unwanted background porosity indications.
- Sound
-
Mechanical vibrations transmitted by an elastic medium.
- Sound Wave
Interference - When
two or more sound waves from different sources are present at the same time,
they interact with each other to produce a new wave.
- Sound Wave
Propagation - The way sound vibrations travel through
different mediums.
- Source
- The origin of radiation; an x-ray tube or a radioisotope.
- Source-Film
Distance - The distance between the focal spot of an x-ray tube or
radiation source and the film; generally expressed in inches.
- Source
Material
- In atomic energy law, any material, except special nuclear material, which
contains 0.05% or more of uranium, thorium, or any combination of the two.
- Spalling
- The cracking and flaking of particles out of a surface.
- Specific
Acoustic Impedance - See acoustic impedance.
- Specific
Activity - The
activity, in curies, of 1 gram of any radioactive source.
- Specific
Gravity - The
ratio of the density of any substance to the density of some other substance
taken as standard
- Specific
Ionization
- Number of ion pair per unit length of path of the ionizing particle in a
medium, e.g. per cm of air or per micron of tissue.
- Spectrum
- The amplitude distribution of frequencies in a signal.
- Spectrum
Response
- The amplification (gain) of a receiver over a range of frequencies.
- Spherical
Wave
- A wave in which points of the same phase lie on surfaces of concentric spheres.
- Spline
- A shaft with a series of longitudinal, straight projections that fit into
slots in a mating part to transfer rotation to or from the shaft.
- Spot
Examination - Local examination of welds or castings.
- Spread Spectrum
- A method of testing material using a correlation
of continuous signals rather than pulse-echo or pitch-catch techniques.
- Spurious
Echo - A general term used for any indication that cannot be associated
with a discontinuity or boundary at the location displayed.
- Squint
Angle
- The angle by which the ultrasonic beam axis deviated from the probe axis.
- Squirter
- See water column.
- Stable
Isotope
- A nuclide that does not undergo radioactive decay.
- Stacked
Crystal - Several crystals cemented together with the daces of the
same polarity in the same direction.
- Stain Ratio
- The ratio of the change in length to the original
length.
- Standard
- A reference object used as a basis for comparison or calibration.
- A concept established by authority, custom or agreement to serve as a model
or rule in the measurement of quantity or the establishment of a practice
or procedure.
- Standing
Wave - A wave in which the energy flux is zero at all points. Such
waves result from the interaction of similar waves traveling in opposite directions
as when reflected waves meet advancing waves. A particular case is that of
waves in a body whose thickness is an integral multiple of half-wavelengths,
as in resonance testing.
- Stepped
Wedge
- A device which is used, with appropriate pentrameters on each step, for
the inspection of parts having great variations in thickness or a complex
geometry. The stepped wedge must be made of material radiographically similar
to that being radiographed.
- Stop
Bath
- A mild acetic acid solution used to arrest film development.
- Storage
Container - A device in which sealed sources are transported or stored.
- Straight
Beam
- An ultrasonic wave traveling normal to the test surface.
- Strain
- A measure of relative change in the size or shape of a body. “Linear
strain” is change (increase or decrease) in a linear dimension. Usually
expressed in inches per inch (in. /in.), or millimeters per millimeter (mm/mm).
- Stress
- Force per unit area, often thought of as a force acting through a small
area within a plane. It can be divided into components, perpendicular and
parallel to the plane, called normal stress and shear stress, respectively.
Usually expressed as pounds per square inch (psi), or megapascales (MPa).
- Stress
Concentration - Changes in contour, or discontinuities, that cause
local increases in stress on a metal under load. Typical are sharp-cornered
grooves, threads, fillets, holes, etc. Effect is most critical when the stress
concentration is perpendicular (normal) to the principal tensile stress. Same
as notch or stress raiser.
- Stress
Corrosion - Preferential attack area under stress in a corrosive
environment, where such an environment alone would not have caused corrosion.
- Stress-Corrosion
Cracking - Failure by cracking under combined action or corrosion
and a tensile stress, either external (applied) or internal (residual). Cracking
may be either intergranular or transgranular, de pending on the metal and
the corrosive medium.
- Stress Measurement
- A measurement of the stress on a given object.
- Striations
-Microscopic ridges or lines on a fatigue fracture that show the location
of the tip or the fatigue crack at some point in time. They are locally perpendicular
to the direction of growth of the fatigue crack. In ductile metals, the fatigue
crack advances by one striation with each load application, assuming the load
magnitude is great enough. Must not be confused with beachmarks, which are
much larger and are formed in a different way.
- Stringers
- In metals that have been hot worked, elongated patterns of impurities, or
inclusions, that are aligned longitudinally. Commonly the term is associated
with elongated oxide or sulfide inclusions in steel.
- Subatomic
Particles - Particles
that are smaller than the atom (protons, neutrons, electrons are the three
main ones).
- Subionization
- When low energy electrons interact with an atom
giving the orbital electrons a little excess energy.
- Substrate
- Layer of metal underlying a coating, regardless of whether the layer is
basis metal.
- Subsurface
Discontinuity - Any discontinuity which does not open onto the surface
of the part in which it exists. Not detectable by liquid penetrant inspection.
- Surface-Breaking
Cracks - Cracks formed on the surface of an object.
- Surface
Probe - A probe for testing surfaces, which has a finite coverage.
The coil is usually pancake in shape.
- Surface Waves
- See Rayleigh wave.
- Survey
- An evaluation of the radiation hazards incident to the production, use,
release, disposal, or presence of radioactive materials or other sources of
radiation under a specific set of conditions. When appropriate, such evaluation
includes a physical survey of the location of materials and equipment, and
measurements of levels of radiation.
- Suspension
- Liquid bath in which a solid is suspended in liquid.
- SV Wave
-
See shear vertical wave.
- Sweep
- The uniform and repeated
movement of a spot across the screen of the cathode ray tube to form the horizontal
baseline.
- Sweep
Delay - A delay in time of starting the sweep after the initial pulse.
Also denotes the control for adjusting the time.
- Sweep
Length - The length of time or distance represented by the horizontal
baseline on an A-scan.
- Swept Frequency
Technique - An eddy current techniques the involves collecting data at
a wide range of frequencies and looking for signal changes as a function of
frequency.
TOP
>>
A
B C
D E
F G
H I
J K
L M
N O
P Q
R S
T U
V W
X Y
Z