T.O. 33B-1-1
Glossary 64
PITCH-CATCH (UT): Used to describe an inspection method in which the ultrasonic energy is emitted by one
transducer element and received by another on the same or adjacent surface.
PITTING: Forming small sharp cavities in a metal surface by nonuniform electrodeposition or by corrosion.
PLANCK’S CONSTANT (RT): A fundamental physical constant; the ratio of the energy of a photon to its frequency.
PLASTIC DEFORMATION: Working of a material beyond its elastic limit to produce a permanent change in
dimensions.
PLASTIC FLOW: Same as PLASTIC DEFORMATION.
PLASTICITY: The ability of a metal to deform nonelastically without rupture.
PLATE PENETRAMETER (STRIP PENETRAMETER) (RT): A plate of material similar to the specimen under
examination, having a thickness of 1 or 2 percent of the specimen thickness, and having holes of different diameters.
PLATED CRYSTAL: Crystal on which metallic surfaces are deposited for protection and/or to give surfaces on which
the electrical potential can be impressed.
PLATEN: That part of a casting machine against which die sections are fastened, or presses against which trim dies are
fastened.
PLATING: Forming an adherent layer of metal upon an object.
PLATING CRACK: See CRACK, PLATING.
PLATE WAVE: See LAMB WAVE.
POINT OF INCIDENCE (UT): Designates the point at which the center of the sound beam leaves the wedge from an
angle beam search unit.
POLARITY: The quality of having two opposite magnetic poles, one north and one south.
POLE (MT): The area on a magnetized part from which the magnetic field leaves or enters the part.
POROSITY: Random pits or holes in the object.
POSITRON: A fundamental particle of nature having a mass equal to that of the electron and possessing a positive
charge equal to the negative charge of the electron. The mass of the positron is therefore 9.107 x 10-28 gm; the
electrical charge carried by the positron is equal to 4.802 x 10-10 statcoulomb (electrostatic unit of charge).
POST-CLEANING (PT): The removal of residual penetrant and/or developer from the item after the inspection
operation.
POST-EMULSIFICATION (PT): The technique wherein a separate emulsifying step is required to facilitate water rinse
removal of the surface penetrant.
POTTER-BUCKY DIAPHRAGM (RT): A device incorporating an anti-scatter grid that is kept in motion during the
time of a radiographic exposure so as to avoid grid images on the radiograph.
POTTER-BUCKY GRID (RT): See POTTER-BUCKY DIAPHRAGM.
