T.O. 33B-1-1
Glossary 24
DIE CASTING:
(1)
A casting made in a die.
(2)
A casting process where molten metal is forced under high pressure into the cavity of a metal mold.
DIE FORGING: A forging whose shape is determined by impressions in specially prepared dies.
DIE LINES: Lines or markings on formed, drawn or extruded metal parts caused by imperfections in the surface of the
die.
DIFFERENTIAL COILS (ET): Two or more coils electrically connected in series opposition such that any
electromagnetic condition which is not common to the areas of the specimen being tested or the test specimen and the
standard will produce an unbalance in the system and thereby be detected.
DIFFERENTIAL MOTTLING (RT): Minor irregularities in the distribution of density over the whole of the
radiograph.
DIFFERENTIAL SENSING: A method of measuring eddy current response in which two coils are used to determine
relative variations between two sections of material. These two sections may be two separate pieces of material (one a
standard, the other the test material).
DIFFRACTION (RT): The scattering of incident radiation from the regularly spaced atoms in crystals or complex
molecules such that interference between the scattered waves results in a pattern of maxima and minima in the intensity
of the scattered radiation.
DIFFRACTION (UT): The deflection of a wave front when passing the edges of an obstacle.
DIFFRACTION MOTTLE (RT): A superimposed mottle or pattern on an image due to diffraction of certain
wavelengths in the incident beam, caused by tile size and orientation of the crystals of the material through which they
have passed.
DIFFRACTION MOTTLING: A diffuse diffraction pattern on a radiograph resulting from X-raying thin sections of
crystalline material.
DIFFUSE INDICATIONS (MT): Indications of some sub-surface indications that are broad, fuzzy, feathery and are not
clearly defined.
DIFFUSE REFLECTION (UT): Rough surface or associate interface reflection of ultrasonic waves from irregularities
of the same order of magnitude or greater than the wavelength.
DIFFUSION:
(1)
Spreading of a constituent in a gas, liquid or solid, tending to make the composition of all parts uniform.
(2)
The spontaneous movement of atoms or molecules to new sites within a material.
DIGGING: A sudden erratic increase in cutting depth or in the load of a cutting tool caused by unstable conditions in
the machine setup. Usually, the machine is stalled or either the tool or the workpiece is destroyed.
DIMENSIONAL STABILITY: Refers to the ability of an alloy to remain unchanged in size or shape after aging,
DIMPLING:
