EUTECTIC ALLOY: The composition in a binary alloy system that melts at the lowest temperature. More than one
eutectic composition may occur in a given alloy system consisting of more than two metals.
EUTECTIC MELTING: Melting of localized micro areas whose composition corresponds to that of the eutectic in the
EVALUATION: The process of deciding as to the severity of the condition after the indication has been interpreted.
Evaluation leads to the decision as to whether the part must be rejected, salvaged or may be accepted for use.
EXFOLIATION: A type of corrosion that progresses approximately parallel to the outer surface of the metal, causing
layers of the metal to be elevated by the formation of corrosion product.
EXPANDED SWEEP (UT): An expansion of the horizontal sweep line or time axis on the viewing screen of the ultra-
sonic instrument. This permits, when used in conjunction with the sweep delay, to more closely scrutinize any portion
of the pattern.
EXPOSURE (RT): The product of the X-ray intensity as measured by filament current in milliamperes and time in
seconds or minutes for X-rays, or the product of source strength in curies and time in seconds or minutes for gamma
rays. The exposure factor determines the degree of film blackening as long as the reciprocity law is valid. See
RECIPROCITY LAW and RECIPROCITY LAW FAILURE.
EXPOSURE CHART (RT): A graph showing the relation between material thickness, kilovoltage, and exposure. It is
only adequate for determining exposure time for a uniform thickness of material.
EXPOSURE DEVICE (RT): A shield in the form of a package designed to contain and allow the controlled use of one
or more sealed sources for the purpose of making radiographic exposures.
EXPOSURE FACTOR (RT): A quantity that combines milliamperage or source strength, time, and distance.
Numerically, the exposure factor is the product of milliamperage and time divided by distance squared for X-rays and
the product of curies and time divided by distance squared for gamma rays.
EXPOSURE FOG (RT): Fog caused by any unwanted exposure of a film to ionizing radiation or light, at any time
between manufacture and final fixing.
EXPOSURE LATITUDE (RT): The range of thickness of a specified material that corresponds to the range of useful
EXPOSURE METER (RT): An instrument for measuring exposure (radiation quantity).
EXPOSURE RATE (RADIATION QUANTITY) (RT): The exposure unit time. Special unit: roentgens per second.
EXPOSURE RATE METER (RT): An instrument for measuring exposure rate (radiation quantity).
EXPOSURE TABLE (RT): A table giving the radiographic exposures suitable for the different thicknesses of a
EXTERNAL DISCONTINUITIES: Surface irregularities that cause density variations on a radiograph. These are
observable with the naked eye.
EXTERNAL DOSE: The portion of the dose equivalent received from radiation sources outside the body.
EXTREMITY: means hand, elbow, and arm below the elbow; foot, knee, and leg below the knee.