- Limiting the duration or decreasing the amplitude of vibrations.
A measure of the ability of a material to dissipate mechanical energy.
Material - A highly absorbent material used to cause rapid decay
of vibration. The
material bonded to the back of the piezoelectric element of a transducer to
limit the duration of vibrations.
Adaptation - The adjustment of the eyes that occurs over time when
one enters a darkened area. This adjustment permits the eye to see better
in the dim lighting conditions.
- Dead Spot
- An area where destructive waves interference occurs to such an extent
that the net effect is zero sound energy in the area.
Zone - In ultrasonic testing, the interval following the initial
pulse where the transducer ring down prevents detection or interpretation
of reflected energy (echoes). In contact ultrasonic testing, the area just
below the the surface of a test object that can not be inspected because of
the transducer is still ringing down and not yet ready to receive signals.
- Removing burrs, sharp edges or fins from metal parts by filing, grinding,
or tumble or vibratory deburring.
- The loss of carbon from the surface of a ferrous
alloy usually resulting from heating the material in certain environments.
- The gradual reduction of the quantity of some substance or energy form to
Radioactive - The spontaneous change of an atomic nucleus and the
emission of a particle or a photon.
- Decay Rate
- The speed at which radioactive decay occurs. For a definite quantity
of a nuclei, the rate of decay is usually expressed in terms of half-life.
- A logarithmic unit for expressing power relationships.
n = 10 log10(I1/I2)
where n is the difference of decibels of intensities 1 & 2.
- The removal of radioactive contaminants from surfaces.
Drawing - The forming of deeply recessed parts by means of plastic
flow of the material.
Etching - Severe etching of a metallic surface for examination at
a magnification of ten diameters or less to reveal gross features such as
segregation, cracks, porosity or grain flow.
- A discontinuity or other imperfection causing a reduction
in the quality of a material or component.
- The sharpness of features on a radiograph that correspond to boundaries
from thickness or material density changes in the radiographed component.
- Deformation within the elastic range caused by a load or force that does
not exceed the elastic limit of the material. Temporary deformation such as
that of a spring.
- A laminar discontinuity such as an area of unbonded materials.
Line - A material (liquid or solid) placed in front of a transducer
to cause a time delay between the initial pulse and the front surface reflection.
- The scattering or reradiation of energy from a discontinuity. The reradiated
energy may include waves of both the incident mode and converted modes (longitudinal
- The process of removing existing magnetism from a part.
- A crystal that has a tree-like branching pattern, being most evident in
cast metals slowly cooled through the solidification range.
- An instrument used to measure the degree of darkening of developed radiographic
- Density -
The mass of a substance per unit volume.
Gradient - The change in density of
a radiographic film as a function of position. The maximum density gradient
of a film is usually called gamma.
Compensation - See distance amplitude correction.
- The depth to which the base metal melted and fused during welding.
of Penetration (Standard) - The depth to which
the eddy current density has decreased to 1/e or 36.8% of the surface density.
Also known as skin depth.
- Removal of the thick layer of oxides formed on some metals at elevated
Interference - A reduction in wave intensity that occurs due to the interaction
of waves that are out of phase.
- A device that determines the presence of or measures the amount of energy,
such as radiation.
- An isotope of hydrogen having one neutron and one proton with an atomic
weight = 2.014.
- The nucleus of a hydrogen-2 (deuterium) atom consisting of one neutron
and one proton. A deuteron is considered a subatomic particle with "unit"
(Penetrant) - A finely divided powder applied over the surface of
a part to help bring out penetrant indications.
(Radiographic) - A chemical solution which reduces exposed silver
halide crystals to metallic silver.
Time - The time between the application of the developer and the
examination of the part for indications.
Materials - Materials that have all paired
electrons in the atoms and thus have no net magnetic moment. The magnetic
permeability of diamagnetic materials is usually very close to 1.
Probe - A probe having two sensing coils
located side-by-side allowing it to convert a floating signals to a low voltage
ground referenced signal to be displayed on a ground referenced oscilloscope.
- Any redistribution in space of the intensity
of waves that results from the presence of an object causing variations of
either the amplitude or phase of the waves.
Mottling - A diffuse diffraction pattern on a radiograph that sometimes
results when thin sections of crystalline material are radiographed.
- (1) the movement or atoms or molecules to new sites within a material. (2)
Spreading of a constituent in a gas, liquid or solid, tending to make the
composition of all parts uniform.
Threshold - The minimum
thickness that a layer of a fluorescent penetrant must reach so that it will
fluoresce when exposed to UV light.
Rupture Fracture - A fractographic term describing ductile fracture
that occurs by the formation and coalescence of microvoides along the fracture
path. Seen at high magnification as tiny cups, or half-voids.
- Direct Current
(DC) - Electrical current that flows in only one direction in a circuit.
Properties - Properties whose magnitude vary depending on the relationship
of the test axis to a specific direction within the material. The variation
results from preferred orientation or from fibering in the structure. Anisotropy.
Image - Image capable of being recognized by sight without the aid
- a break in the continuity of a medium or material.
Nuclear - A spontaneous nuclear transformation (radioactivity) characterized
by the emission of energy and/or mass from the nucleus.
- A discontinuity in the structure of a crystal. Two basic linear types are
recognized, but combinations and partial dislocations are most prevalent.
An "edge dislocation" corresponds to the row of mismatched atoms
along a straight edge formed by an extra, partial plane of atoms within the
body of the crystal, that is, by a parallel section through the crystal. A
"screw dislocation" corresponds to the highly distorted lattice
adjacent to the axis of a spiral structure in a crystal, the spiral structure
being characterized by a distortion that has joined normally parallel planes
together to form a continuous helical ramp winding about the dislocation as
an axis with a pitch of one interplanar distance.
- The variation of phase velocity with frequency. In general, any process
separating radiation into components having different frequencies, energies,
velocities, or other characteristics.
Medium - A medium in which the propagation velocity depends on the
Amplitude Correction (DAC) - Compensation of gain as a function of time
for difference in amplitude of reflections from equal reflectors at different
sound travel distances. Refers also to compensation by electronic means such
as swept gain, time corrected gain, time variable gain and sensitivity time
Blocks - A set of ultrasonic reference specimens in which each specimen
has a different metal path length to a equal-sized reflector. The specimens
are used to develop distance amplitude response curves.
Response Curve - A curve showing the relationship between signal
amplitude and equal-sized reflecting surfaces at various distances from the
transducer. Standard blocks are used to obtain such curve.
Field - A magnetic field that does not follow a straight path or
have a uniform distribution due to the irregular in shape of the magnetized
test object. The direction of a magnetic field in a symmetrical object will
be substantially uniform if produced by a uniformly applied magnetizing force,
as in the case of a bar magnetized in a solenoid.
- A Change in the shape of a part due to the action of mechanical forces.
- An improper term used to describe the spreading of ultrasonic waves beyond
the near field. It is a function of transducer diameter and wavelength in
- A substructure in a ferromagnetic material within which all the elementary
magnets (electron spins) are held aligned in one direction by interatomic
forces; if isolated, a domain would be magnetically saturated.
- Doppler Effect
- The change in the observed frequency of an acoustic or electromagnetic
wave due to relative motion of the source and the receiver.
- The amount of ionizing radiation energy absorbed per unit mass of irradiated
material at a specific location, such as a part of the human body. Measured
in reps, rems per hour.
- A device that measures radiation dose, such as a film badge or
Time - The period of time allowed for excess liquid to gradually
flow off of a part after application of either the penetrant or emulsifier
Developer - A powder that is applied dry to the test component when
performing a penetrant inspection.
Ratio - The working distance for the X-ray tube in relation to the
film distance. The working distance, d, and the specimen thickness, t, are
both measured with reference to the source side of the specimen.
- Dual Element
An ultrasonic transducer that has two active elements in one case. One of
the elements send the sound wave and the second receives the reflected sound
energy. Near surface resolution is improved since there is no dead-zone issue
to content with.
– Permitting plastic (or permanently) prior to eventual fracture.
Crack Propagation - Slow crack propagation that is accompanied by
noticeable plastic deformation and requires energy to be supplied from outside
- The ability of a material to deform plastically without fracturing of
area in a tensile test or by other means.
- Dwell Time
- The period of time wherein penetrant or developer is in contact with
the surface of the part. Drain time is considered to be a portion of the dwell
time. Synonymous with penetration time or emulsifier time.
- Moving, or having high velocity. Frequently used with impact testing of
metal specimens. Opposite of static, or essentially stationary, testing or
Creep - Creep that occurs under conditions of fluctuating load or
Range – The ratio of maximum to minimum reflective areas that
can be distinguished on the cathode ray tube at a constant gain setting.