STEP-WEDGE COMPARISON FILM (RT): A strip of processed film carrying a stepwise array of increasing
STEP-WEDGE PENETRAMETER (STEP PENETRAMETER): A penetrameter of similar material to the specimen
under examination, having steps ranging usually from 1 to 5 percent of the specimen thickness. Each step may contain
one or more drilled holes for the assessment of definition.
STEPPED WEDGE (RT): A device that is used, with appropriate penetrameters on each step, for the inspection of
parts having great variations in thickness or a complex geometry. The stepped wedge must be made of material
radiographically similar to that being radiographed.
STEREOFLUOROSCOPY (RT): The production of a pair of radiographs suitable for stereoscopic viewing.
STEREORADIOGRAPHY (RT): The process of finding the position and dimensions of details within a specimen by
measurements made on radiographs taken from different directions.
STEREOSCOPIC (RT): A type of viewing that employs an optical instrument (stereoscope) to combine the images of
two radiographs taken from slightly different angles, thus achieving a three-dimensional effect.
STEREOSCOPY (RT): The three-dimensional visual effect resulting from binocular vision.
STIFFNESS: The ability of a metal or shape to resist elastic deflection. For identical shapes, the stiffness is
proportional to the modulus of elasticity.
STOCHASTIC EFFECTS: The health effects that occur randomly and for which the probability of the effect occurring,
rather than its severity, is assumed to be a linear function of dose without threshold. Hereditary effects and cancer
incidence are examples of stochastic effects.
STOP BATH (RT): A chemical solution (or clean running water) used for arresting the activity of the developer
remaining in the film emulsion.
STORAGE FOG (RT): Fog caused by storing film in a high humidity/temperature environment.
STRAIGHT BEAM (UT): A vibrating pulse wave train traveling normal to the test surface.
STRAIN: The change per unit of length in a linear dimension of a stressed body. It may be thought of as the
deformation caused by an applied load and is measured in inches of change per inch of stressed length, or in percentage
of dimensional change of a specified stressed length.
STRAIN AGING: Aging induced by cold working.
The work done in deforming a body.
The work done in deforming a body within the elastic limit of the material. It is more properly elastic
strain energy and can be recovered as work rather than heat.
STRAIN HARDENING: An increase in hardness and strength caused by plastic deformation at temperatures lower
than the recrystallization range.
STRAY RADIATION (RT): Radiation other than the useful beam. It includes leakage, secondary, and scattered