153 - A radioisotope of the element gadolinium.
A control which varies the amplification of the ultrasonic system. Also considered
the sensitivity control.
Corrosion - Corrosion associated with the current of a galvanic cell
consisting of two dissimilar conductors in an electrolyte or two similar conductors
in dissimilar electrolytes. Where the two dissimilar metals are in contact,
galvanic corrosion may occur.
Series - A series of metals and alloys arranged according to their
relative corrosive tendency in a given environment. The most common environment
is sea water or other concentrations of salt in water.
- An instrument with a bar of iron wrapped with an electrical wire and
a magnet that detects electrical current.
Radiation - high-energy, short wavelength electromagnetic radiation
emitted by a nucleus. Energies of gamma rays are usually between 0.010 and
10 mev. X-rays also occur in this energy range, but are non-nuclear origin.
Gamma radiation usually accompanies alpha and beta emissions and always accompanies
fission. Gamma rays are very penetrating and are best attenuated by dense
materials like lead and depleted uranium.
- Holes created by a gas escaping from molten metal.
Holes (on radiograph) - Appear as round or elongated,
smooth-edged dark spots, occurring individually, in clusters or distributed
throughout the casting.
Porosity - A cavity caused by entrapped gas. Essentially a smooth-sided
bubble within the metal, where the metal solidified before the gas could escape
to the atmosphere. Also called gas pocket.
- An electronic device for monitoring signals in a selected segment of the
trace on an A-scan display.
- The interval along the baseline that is monitored.
- Gauss (B)
- Unit of flux density or induction. The strength of field induced in a ferromagnetic
body is described as being so many gausses. Numerically, one gauss is one
line of flux per square centimeter of area.
A radiation detection and measuring instrument. It contains a gas filled tube
which discharges electrically when ionizing radiation passes through it. Discharges
are counted to measure the radiation's intensity.
Resolution - Radiograph resolution is effected by source to film distance,
object to film distance and source size.
- An indication arising from certain combinations of pulse repetition frequency
and time base frequency. See wrap around.
- The more common term for crystal, a three-dimensional array of atoms having
a certain regularity in its internal arrangement. The grain is composed of
many cells, or lattices, in which the atoms are arranged on the metal involved.
Boundary - The boundary between two grains.
- Grain Noise
Modeling - Methods used to predict the electrical
voltage signals seen during ultrasonic inspections of metal components.
Size - Size of the crystals in metal when compared with a standard.
Usually referred to as being fine, medium, or coarse.
- A film characteristic resulting from the grouping or clumping together of
the countless small silver grains into relatively large masses visible to
the naked eye or with slight magnification.
- Those individual crystals that make up the crystalline structure of metal.
- See background noise.
- Pressing down or together with a crushing turning
motion, rubbing harshly or gratingly.
Cracks - Shallow cracks formed in the surface of relatively hard
materials because of excessive grinding heat or the high sensitivity of the
Porosity - In weld metal or in casting, pores, gas holes or globular
voids that are larger and in greater number than obtained in good practice.
Velocity - The rate at which the envelope of an ultrasonic pulse
(many frequencies) propagates through the medium.