- Pair Production
- An absorption process
for X and gamma radiation in which the incident photon is annihilated in the
vicinity of the nucleus of the absorbing atom, with subsequent production
of an electron and positron pair.
open curve which all points are equidistant from a fixed point and a straight
Circuit - A
circuit in which the current has two or more paths to follow.
(and diamagnetic) - All materials are affected by magnetic fields.
Those which are attracted are called paramagnetic. The reaction to a magnetic
field of these two classes of substances is very slight indeed. The few materials
that are strongly attracted by magnetic fields are called ferromagnetic.
- A material property or instrument variable.
- See spurious echo.
units of matter and energy.
- Movement of particles of material during wave propagation.
Radiation - A
stream of atomic or subatomic particles.
- The property of a penetrant that causes it to find its way into very fine
openings, such as cracks.
- A device for measuring the penetrating power of radiation.
- A fluid (usually a liquid but can be a gas) which possesses unique properties
that render it highly capable of entering small openings, a characteristic
which makes this fluid especially suitable for use in the detection of surface
discontinuities which may be present.
Testing (PT) - Method that is used to reveal surface
breaking flaws by bleedout of a colored or fluorescent dye from the flaw.
Ultrasonic - Propagation of ultrasonic energy into a material. See
also effective penetration.
- The shadow cast
when the incident radiation is partly, but not wholly cut off by an intervening
body; the space of partial illumination between the umbra, or perfect shadow
or all side and the full light. A marginal region on borderland or partial
Shadow - The shadow of an object with an appreciable
size has two distinct regions; one of full-shadow, called the umbra, the other
of half-shadow, called the penumbra shadow.
Table - A chart that
lists all of the known elements.
Magnets - An object that once magnetized will maintain
the properties of magnetism indefinitely.
- The ease with
which a magnetic flux can be established in a given magnetic circuit.
(Magnetic) - Ratio between flux density, B, and magnetizing force, H.
Permeability describes the intrinsic willingness of a material to conduct
magnetic flux lines.
monitoring equipment - Devices designed to be worn or carried by
an individual for the purpose of measuring the dose received (e.g. film badges,
pocket chambers, pocket dosimeters, film rings, etc.).
- Any effect that causes a small change in a physical system and/or changes
the value of some given function.
- A reference standard used to verify the performance of medical diagnostic
- Phase Angle
- The difference in phase between two sinusoidal varying quantities.
Array - A mosaic of transducer elements in which the timing of the
elements’ excitation can be individually controlled to produce certain
desired effects, such as steering the beam axis or focusing the beam.
- Phase Lag
- A lag in phase (or time) between the sinusoidal currents flowing at
the surface and those below the surface.
Velocity - The velocity of a single frequency continuous wave.
- A vector describing sinusoidal signals; It has both amplitude and phase.
(PD) - the process by which an x-ray photon is captured
by the nucleus of the atom with the ejection of a particle from the nucleus
when all the energy of the x-ray is given to the nucleus.
(PE) - A
substance is photoelectric if it ejects electrons when light strikes it.
absorption - A process by which electromagnetic radiation
imparts energy to matter.
Effect - When
charged particles are released from a material when it absorbs radiant energy.
Imaging (PI) - A
powerful, high-resolution scanning and imaging tool
- Photon -
elementary particle of electromagnetic energy; light.
properties - The properties of a material that are relatively insensitive
to structure and can be measured without the application of force. Examples
are density, melting temperature, damping capacity, thermal conductivity,
thermal expansion, magnetic properties, and electrical properties.
- Pierre &
Marie Curie - Two scientists that discovered
Effect - The ability of certain materials to convert electrical energy
into mechanical energy and vice versa.
Element - A
material that vibrates when an electric current passes through it.
Transducers - A tool that takes an electrical signal
and turns it into mechanical vibrations, or takes vibrations and turns it
into an electrical signal.
- A container usually made of lead or U 238 used to shield radioactive sources
when not in use.
- expansion test - A test for determining the ability of tubes to be expanded
or for revealing the presence of cracks or other longitudinal weaknesses,
made by forcing a tapered pin into the open end of a tube.
- (1) then central cavity formed by contraction in metal, especially ingots,
during solidification; (2) the defect in wrought or cast products resulting
from such a cavity; (3) an extrusion defect due to the oxidized surface of
the billet flowing toward the center of the rod at the back end; (4) a tubular
metal product, cast or wrought.
- Pitch -
The property of sound that varies with frequency (high and low sounds are
at different pitches).
-A term describing a test method in which the ultrasonic energy is emitted
by one transducer and received by another on the same or opposite surface.
Line - The location on a gear tooth, approximately midway up the
tooth, that crosses the pitch circle, or the equivalent-size disk that could
geometrically replace the gear.
- An ore which contains uranium.
- Small cavities in a metal surface by nonuniform electrodeposition or by
- Planck Constant
- The fundamental constant equal to the ratio of
the energy of a quantum of energy to its frequency.
Wave - wave in which points of same phase lie on parallel plane surfaces.
Deformation - Deformation that remains after removal of the load
or force that caused the deformation, or change of shape. Same as permanent
Wave - See lamb wave.
- Crystal on which metallic surfaces are deposited for protection and/or to
produce surfaces on which the electrical potential can be impressed.
- Denotes the point at which the center of the sound beam leaves the plastic
wedge of an angle beam transducer and enters the test object. See probe index.
- The process of confining the vibrations of the
vector constituting a transverse wave to one direction.
- The process of reorienting crystal domains in certain materials by applying
a strong electric field at elevated temperatures. Materials (usually ceramics)
so treated exhibit piezoelectric behavior.
- Pertaining to a solid metal composed of many crystals, such as an ordinary
- (1) Small voids in the body of a metal; (2) In powder metallurgy - minute
cavities in a compact, sometimes intentional; (3) minute perforations in an
- The property of being porous.
Nuclear particle with the mass of an electron but opposite charge (an anti-electron).
Penetrant - A type of penetrant containing no emulsifier, but which
is cleaned from a surface with water after applying an emulsifier as a separate
step. The term is often abbreviated as "P.E." penetrant, or "P.E."method.
Energy - Potential
energy is stored energy, energy that can be released or harnessed to do work.
(Penetrant ) - The cleaning of parts before testing so that they
are free from all foreign material (paint, grease, oil, rust, scale, layout
dye, was crayon markings, etc.) which could cover a surface discontinuity
and thereby inhibit the entrance of the penetrant liquid.
- The method used to show ultrasonic information. This may include A-scans,
B-scans or C-scans, displayed on various types of recorders or cathode ray
- Radiation arising directly from the target of an x-ray tube or from a radioactive
Reference Response Level - The ultrasonic response from the basic
calibration reflector at the specified sound path distance, electronically
adjusted to a specified percentage of full screen height.
Field - The magnetic field surrounding the coil due to the current
flowing through it.
- The normal stresses on three mutually perpendicular planes on which there
are no shear stresses.
- Eddy current transducer.
- The point on a shear wave or surface wave transducer through which the emergent
beam axis passes.
- Two handheld electrodes which are pressed against the surface of a part
to make contact for passing magnetizing current through the metal. The current
passing between the two contacts creates a field suitable for finding defects
with magnetic particles.
- Advancement of a wave through a medium.
Limit - The maximum stress at which strain remains directly proportional
to stress; the upper end of the straight-line portion of the stress-strain
or load-elongation curve.
- Protons -
fundamental particle usually found in the nucleus of an atom with a positive
- Acronym for pounds per square inch, a unit of measurement for stress, strength,
and modulus of elasticity.
- A transient electrical or ultrasonic signal.
Echo Method - An ultrasonic test method in which discontinuities
are detected by return echoes from the transmitted pulses.
Test - A
test that can determine the location of a discontinuity by measuring the time
required for a short ultrasonic pulse to travel through the material.
- Pulsed Eddy
Current - An electromagnetic test technique that drives eddy currents using a pulse of electrical current. The technique is particularly useful in driving eddy currents deeper into materials than is usually achievable with conventional eddy current techniques. The signal is often displayed in the time domain which allows for depth gating and other useful signal processing techniques.
Length - A measure of pulse duration expressed in time or number
Use of ultrasonic equipment that generated a series of pulses which are separated
from each other be a constant period of time, i. e., energy is not sent our
- Number of pulses that are transmitted in a unit time (also called pulse
- Pulser-Receiver -
Used with a transducer and oscilloscope for flaw detection and thickness gauging.
Repetition Frequency - See repetition rate.
Tuning - Control of pulse frequency to optimize system response.