T.O. 33B-1-1Glossary 64PITCH-CATCH (UT): Used to describe an inspection method in which the ultrasonic energy is emitted by onetransducer 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 indimensions.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 underexamination, 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 whichthe electrical potential can be impressed.PLATEN: That part of a casting machine against which die sections are fastened, or presses against which trim dies arefastened.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 anangle 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 positivecharge equal to the negative charge of the electron. The mass of the positron is therefore 9.107 x 10-28 gm; theelectrical 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 inspectionoperation.POST-EMULSIFICATION (PT): The technique wherein a separate emulsifying step is required to facilitate water rinseremoval of the surface penetrant.POTTER-BUCKY DIAPHRAGM (RT): A device incorporating an anti-scatter grid that is kept in motion during thetime of a radiographic exposure so as to avoid grid images on the radiograph.POTTER-BUCKY GRID (RT): See POTTER-BUCKY DIAPHRAGM.
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