- Discontinuity due to lack of union between weld metal and parent metal.
Wave -A type of ultrasonic wave propagation in which the wave is
guided between two parallel surfaces of the test object. The mode and velocity
depend on the product of the test frequency and the separation between the
- Lamb Wave
Generation - Lamb waves are similar to longitudinal
waves but are bounded by the sheet or plate surface causing a wave-guide effect.
- Plate-like; made of a number of parallel plates or sheets. Usually applied
to microstructure. The most common lamellar microstructure is pearlite in
- Metal defects with separation or weakness generally aligned parallel to
the worked surface of the metal. May be the result of pipe, blisters, seams,
inclusions or segregation elongated and made directional by working. Lamination
defects may also occur in metal-powder compacts.
- A surface defect, appearing as a seam, caused by folding over hot metal,
fins or sharp corners and then rolling or forging them into the surface, but
not welding them.
- Latent Image
- The invisible image on exposed film which has
not been developed.
(Radiographic) - The range of thickness of material that can be recorded
on the radiograph within the useful reading range of film density. A high
contrast film has little latitude and conversely a low contrast film has great
Test - A test on sealed sources to assure that radioactive material
is not being released.
- Leak Testing
(LT) - Techniques are used to detect and locate
leaks in pressure containment parts, pressure vessels, and structures.
- Leakage Field
- The magnetic field formed outside of a magnet when there is a crack in the
Rule - If you place your left hand around the conductor
and close your fist on it with your thumb pointing toward the direction of
- Lenz's Law
- An induced current has a direction such that
its magnetic field opposes the change in magnetic field that induced the current.
Material - Source material, special nuclear material or byproduct
material received, possessed, used or transferred under a general or special
license issued by the Atomic Energy Commission.
- Distance between the coil of a surface probe and sample. It is a measure
of coupling between probe and sample.
Metal - One of the low-density metals such as aluminum magnetism,
titanium, beryllium or their alloys.
- Linear Accelerator
- A particle accelerator designed to move charged
particles at high velocities along a straight path to a target.
Elastic Fracture Mechanics - method of fracture analysis that can
determine the stress (or load) required to induce fracture instability in
a structure containing a crack-like-flaw of known size and shape.
Amplitude - A measure of the proportionality of the signal input
to the receiver and the amplitude of the signal appearing on the display of
the ultrasonic instrument or on an auxiliary display.
Area - Constant proportionality between the signal amplitude and
the areas of equal discontinuities located at the same depth in the far field.
Necessarily limited by the size of the ultrasonic beam and configuration of
Focus Principle - The process of making the angle between the anode
face and the central ray such that the effective focal spot is small in relation
to the actual spot size.
of Force - The lines that can be produced by a permanent magnet or
a use of a sheet of paper and iron filings are called "magnetic lines
of force". These lines are imaginary lines, but the concept is convenient
for describing a magnetic field. A magnetic field has an intensity of so may
lines per square inch. These lines have a definite direction and always form
closed loops and return back onto themselves.
- An apparatus used to accelerate electrons to high velocities by means of
a high frequency electrical wave traveling along a tube in the linear direction
of the electron beam.
-The characteristic of an instrument that is revealed by a linear change in
reflected signal amplitude. The vertical linearity is determined by plotting
the change in ratios of signal amplitude from two reflecting areas. The horizontal
linearity is determined by plotting the distance the signal is displaced along
the sweep against the change in material thickness.
Emulsifiers - Oil-based emulsifiers that are able to mix with
penetrants regardless of the concentration.
- Liquid Penetrant
Inspection (LPI) - A method that is used to reveal
surface breaking flaws by bleedout of a colored or fluorescent dye from the
- Load -
A device that uses electrical power.
- The natural logarithm of the ratio of the amplitudes of two successive cycles
in a damped wave train.
- Lengthwise, or in an axial direction.
Direction - The principal direction of flow in a worked metal.
Magnetization - Magnetization of a material in such a way that the
magnetic flux runs substantially parallel to the long axis of the part, the
flux path completing itself through the air outside the material. It is sometimes
called bipolar magnetization, because at least two external poles exist in
Waves - Commonly used term for compressional wave.
- Rate of propagation of a wave parallel to the direction of motion of the
- A single turn of wire or cable used to carry electric current. It is used
for magnetizing and demagnetizing purposes.
of Back Reflection - Absence or significant reduction of an indication
from the back surface of the test Object.
Fatigue - Fatigue that occurs at relatively small numbers of cycle,
or stress applications. The numbers of cycles may be in the tens, hundreds,
or even thousands of cycles. There is no exact dividing line between low-
and high- cycle fatigue, but for practical purposes, low-cycle fatigue may
be accompanied by some plastic, or permanent, deformation.
penetrant - A penetrant material or system specifically designed
to be compatible with or nonreactive in the presence of liquid oxygen.