Indication - A test indication that could be interpreted as originating
from a discontinuity but which actually originates where no discontinuity
Michael - a chemist in England during the
early 1800's and is credited with the discovery of electromagnetic induction,
electromagnetic rotations, the magneto-optical effect, diamagnetism, and many
Law - the principle saying that whenever
wires are moved with an electrical current, it creates a magnetic field.
- The zone beyond the near field in front of the transducer in which signal
amplitude decreases monotonically in proportion to distance from the transducer.
Also called the Fraunhofer zone.
Film - Radiographic film which has inherent graininess characteristics
of a coarse nature intended to increase the relative film speed.
- The phenomenon leading to fracture under repeated or fluctuating stresses
having a maximum values less than the tensile strength of the material. Fatigue
fractures are progressive, beginning as minute cracks that grow under the
action of the fluctuating stresses.
Cracks in a material formed from repeated stress, none of which exceeded the
maximum stress of the material.
Limit - The maximum stress below which a material can presumably
endure an infinite number of stress cycles. If the stress is not completely
reversed, the value of the mean stress, the minimum stress, or the stress
ratio should be stated.
Strength - The maximum stress that can be sustained for a specified
number of cycles without failure, the stress being completely reversed within
each cycle unless otherwise stated.
Coil - See encircling probe.
- Essentially pure iron in the microstructure of an iron or steel specimen.
It may have a small amount of carbon (less than 0.02 wt%). Also called alpha
- It is a measure of coupling between the coil and test object.
- Fraction of the test coil area filled by the test specimen.
that can be magnetized.
- Describing a metal that is more than 50% iron, such as steel, stainless
steel, cast iron, ductile (nodular) cast iron, etc.
Intensity - A
term used to describe the strength of the electromagnetic field.
- a radius (curvature) imparted to inside meeting surfaces; a blended curve
joining an internal corner to two lateral surfaces.
Crack - A crack-like discontinuity, open to the surface, but filled
with some foreign material-oxide, grease, etc.- which tends to prevent penetrants
Badge - A package of photographic film worn like a badge by workers
in the nuclear industry to measure exposure to ionizing radiation. The absorbed
dose can be calculated by the degree of film darkening caused by the irradiation.
Holder - A light tight carrier for films and screens.
Speed - Relative exposure required to attain a specified density.
- A layer of absorption material that is placed in the beam of radiation for
the purpose of absorbing rays of certain wavelengths and thus controlling
the quality of the radiograph.
- Filters in
Radiography - Filters are placed in the x-ray beam
to produce a cleaner image by absorbing the lower energy x-ray photons that
tend to scatter more.
Inherent - The filtration exhibited by the walls and other materials
of a radiation source through which the radiation must pass before it is utilized.
Crack - A discontinuity in a solid material with a very fine opening
to the surface, but possessing length and depth greater than the width of
this opening; usually depth is many time the width.
- Fission -
A term defined as the splitting of an atomic nucleus into two smaller
nuclei of roughly equal mass. During fission, a fissionable nucleus
(such as plutonium) absorbs a neutron, becomes unstable and splits into two
nuclei, releasing energy.
Products - Nuclei formed by the fission of heavy elements. They are
of medium atomic weight, and almost all are radioactive. Examples: strontium
90, cesium 137.
- Any material readily fissioned by slow neutrons, for example, uranium 235
and plutonium 239.
- A chemical solution which dissolves unexposed silver halide crystals from
developed film emulsions.
- Short discontinuous internal fissures in ferrous metals attributed to stresses
produced by localized transformation and decreased solubility of hydrogen
during cooling after hot working. In a fractured surface, flakes appear as
bright silvery areas; on an etched surface they appear as short, discontinuous
cracks. Also called "shatter cracks and snowflakes."
Point Interference - A method used to reconstruct
a flaw based on an general ellipsoid model.
Bottom Hole - A type of reflector commonly used in reference standards.
The end (bottom) surface of the hole is the reflector.
- A defect.
Location Scale - A specially graduated ruler that can be attached
to an angle beam transducer to relate the position of an indication on the
cathode ray tube screen to the actual location of a discontinuity within the
Reconstruction - The process used to determine
what a flaw looks like through nondestructive testing.
Radiographic - The emission of electromagnetic
radiation by a substance as the result of the absorption of electromagnetic
or corpuscular radiation having greater unit energy than that of the fluorescent
radiation. Fluorescence is characterized by the fact that it occurs only so
long as the stimulus responsible for it is maintained. The characteristic
x-radiation emitted as a result of absorption of x-rays of higher frequency
is a typical example of fluorescence.
Penetrant - Property of emitting light as the result of, and only
during the absorption of radiation from some other energy source.
- A bright vivid color that glows under a black light.
Dye - A dye which becomes fluorescent giving off light, when it is
exposed to short wave radiation such as ultraviolet or near ultraviolet light.
Dye Penetrant - A highly penetrating liquid used in performance of
of liquid penetrant testing and characterized by its ability to fluoresce
under black light.
Minerals - Minerals that glow when exposed to sunlight.
Screen - The coating of material in cathode ray tubes, which glows
under electronic bombardment from the cathode.
- Flux, Neutron
- The intensity of neutron radiation. It is expressed as the number of
neutrons passing through 1 square centimeter in 1 second.
- The number of flux lines per unit of area, measured at right angles to the
direction of the flux. It is the measure of magnetic field strength.
Leakage - Flux, or lines of force, leaking from pole to pole outside
Distance (ffd) - The distance in inches between the focal spot of the
x-ray tube, or the radiation source, and the film.
- The distance before and after the focal point in which the intensity differs
a specified amount (usually 6db) from the focal intensity. Also called depth
of field or depth of focus.
Beam - A sound beam that converges to a cross section smaller than
that generated by the transducer.
- A transducer that produces a focused sound beam.
- Concentration or convergence of energy into a small beam.
- A darkening of the film resulting from chemical action of the developer,
aging, scattered secondary radiation, pre-exposure to radiation or exposure
to visible light.
- Metal in sheet form less than 0.006 inch in thickness.
Scatter - Radiation scattered in approximately the same direction
of the primary beam.
Currents Method - In France the eddy current method is known as the
"Foucault Currents" method.
- Descriptive treatment of fracture, especially in metals, with specific reference
to photographs of he fracture surface. Macrofractography involves photographs
at low magnification, microfractography at high magnification.
- A break, or separation, of a part into two or more pieces.
Mechanics - A quantitative analysis for evaluating structural behavior
in terms of applied stress, crack length, and specimen or machine component
Toughness - A generic term for measures of resistance to extension
of a crack. The term is sometimes restricted to results of fracture mechanics
tests, which are directly applicable in fracture control. However, the term
commonly includes results from simple tests of notched or precracked specimens
not based on fracture mechanics analysis. Results from tests of the latter
type are often useful for fracture control, based on either service experience
or empirical correlations with fracture mechanics tests.
Diffraction - A form of diffraction in which the
light source and the receiving screen are in effect at infinite distances
from the diffracting object, so the wave fronts can be treated as planar rather
- Free Electron
- An electron that is produced when the valence electron in any atom
gains sufficient energy from some outside force and then breaks away from
the parent atom.
number of waves that pass a given point in a specified unit of time.
Fundamental – In resonance testing, the frequency at which
the wavelength is twice the thickness of the test material.
Pulse Repetition - The number of pulses per second.
Response - The range of frequencies over which a
device operates as expected.
Test - The nominal ultrasonic wave frequency used in a test.
Wear - Surface damage to a metal part resulting from microwelding
due to slight movement in a nearly stationary joint. Also called fretting
Surface - The first surface of the test object encountered by the
ultrasonic beam. See interface.
Wave Rectified Single Phase AC-
Rectified alternating current for which the rectified is so connected that
the reverse half of the cycle is "turned around," and fed into the
circuit flowing in the same direction as the first half of the cycle. This
produces pulsating dc, but with no interval between the pulses. Such current
is also referred to as single-phase full-wave dc.
Wave Rectified Three Phase AC - When tree-phase alternating current
is rectified the full-wave rectification system is used. The result is dc
with very little pulsation in fact only a ripple of varying voltage distinguishes
it from straight dc.
Generators - A device that generates a function
wave such as a sine wave or square wave.
- Fusion -
This is a particular process, also known as charged particle bombardment,
that yields radioisotopes that are not readily available by the neutron bombardment
or fission process.