MILLICURIE-HOUR (RT): A term used to quantify radiographic exposures made with a gamma-ray source. It is the
product of the activity of the source in millicuries and the exposure time in hours.
MILLIROENTGEN (mR): One-thousandth of a roentgen.
MINIATURE ANGLE BEAM BLOCK (UT): Specific type of reference standard primarily used for the angle beam
method, but also used for the straight beam and surface wave methods.
MINIATURE-FILM RADIOGRAPHY (MASS MINIATURE RADIOGRAPHY) (RT): Fluorography using miniature
MISCIBLE (PT): The tendency of capacity of two or more liquids to form a uniform blend, that is, to dissolve in each
other; degrees are total miscibility, partial miscibility, and immiscibility.
MISRUN: A casting not fully formed, resulting from the metal solidifying before the mold is filled.
MISRUNS (RADIOGRAPHIC): Appears as prominent darkened areas of variable dimensions with a definite smooth
MOBILITY (MT): The ease with which magnetic particles move over the surface of a magnetized part and accumulate
at a discontinuity exhibiting polarity.
MODE: The manner in which acoustic energy is propagated through a material as characterized by the particle motion
of the wave.
MODE CONVERSION (UT): Changing from one mode of vibration to another; caused by retraction at an interface.
MODE OF VIBRATION (UT): Type of wave motion; e.g., longitudinal, transverse, etc. Three common modes of
vibration used in ultrasonic inspection are longitudinal, transverse, and surface wave modes.
MODULATION ANALYSIS (ET): An instrumentation method used in eddy current testing which separates responses
based on their frequency or rate of response. For instance, slow responses from gradual dimension changes can be
separated from rapid responses from a crack.
MODULUS OF ELASTICITY: The ration of stress to the corresponding strain within the limit of elasticity.
MODULUS OF RUPTURE: Nominal stress at fracture in a bend test or torsion test.
MOLD: A form or cavity into which molten metal is poured to produce a desired shape. Molds may be made of sand,
plaster or metal and frequently require the use of cores and inserts for special applications.
MOLECULE: The smallest unit quantity of matter that can exist by itself and retain all the properties of the original
substance. Molecules are formed by the chemical combination of atoms.
MONITORING (RT): Periodic or continuous determination of the amount of ionizing radiation or radioactive
contamination present in an occupied region.
MONOCHROMATIC: (Homogeneous) of the same wavelength.
MOTTLING (RT): Large graininess effect on a radiograph that may be due to diffraction by large grain structures in
materials, or can be caused by the use of fluorescent screens. Mottling is readily distinguishable from film graininess
because of its coarse appearance and lack of definition.
MOVEMENT UNSHARPNESS (RT): See UNSHARPNESS.