T.O. 33B-1-1Glossary 24DIE 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 thedie.DIFFERENTIAL COILS (ET): Two or more coils electrically connected in series opposition such that anyelectromagnetic condition which is not common to the areas of the specimen being tested or the test specimen and thestandard 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 theradiograph.DIFFERENTIAL SENSING: A method of measuring eddy current response in which two coils are used to determinerelative variations between two sections of material. These two sections may be two separate pieces of material (one astandard, the other the test material).DIFFRACTION (RT): The scattering of incident radiation from the regularly spaced atoms in crystals or complexmolecules such that interference between the scattered waves results in a pattern of maxima and minima in the intensityof 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 certainwavelengths in the incident beam, caused by tile size and orientation of the crystals of the material through which theyhave passed.DIFFRACTION MOTTLING: A diffuse diffraction pattern on a radiograph resulting from X-raying thin sections ofcrystalline material.DIFFUSE INDICATIONS (MT): Indications of some sub-surface indications that are broad, fuzzy, feathery and are notclearly defined.DIFFUSE REFLECTION (UT): Rough surface or associate interface reflection of ultrasonic waves from irregularitiesof 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 inthe 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:
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