LINE FOCUS PRINCIPLE (RT): The process of making the angle between the anode face and the central ray such that
the effective focal spot is small in relation to the actual spot size.
LINE-FOCUS TUBE (RT): An X-ray tube in which the electron focus is approximately a rectangle and the foal spot
size is approximately a square.
LINES OF FORCE (MT): Imaginary lines used to visualize the magnetic field.
LIMITS (dose limits): The permissible upper bounds of radiation doses.
LIPOPHILIC (PT): An oil based liquid used in penetrant inspection to make penetrant oil water-washable.
LIQUID VEHICLE (MT): The liquid in which the magnetic particles are suspended to facilitate their application.
LOCALIZING CONE (COLLIMATING CONE) (RT): A cone that limits the divergence of a beam of radiation.
LONGITUDINAL MAGNETIZATION (MT): Magnetization of a material in such a way that the magnetic lines of
force are essentially parallel to the test parts longitudinal axis.
LONGITUDINAL WAVE (UT): A type of wave in which the particle motion of the material is essentially in the same
direction as the wave propagation.
LOSS OF BACK REFLECTION (UT): Absence of an indication of the far surface of the article being inspected.
LUDERS LINES: Lines that are produced on the surface of low carbon steel by deforming the metal just past the yield
LUMEN (PT, MT): A measure of the brightness of light. A unit of luminous flux equal to the light emitted in a unit
solid angle by uniform point source of one candle.
LUMINESCENCE (RT): A phenomenon in which the absorption of radiation by a substance gives rise to the emission
of light characteristic of the substance.
MACMNEABILITY: Refers to the ease and speed with which a metal may be cut (with free chip removal) to produce a
reasonably smooth surface.
MACHINED SURFACE: The metal surface left by the cutting tool.
MACHINING: Removing material, in the form of chips, from work, usually through the use of a machine.
MACHINING STRESS: Residual stress caused by machining.
MACRO-ETCH: Etching of a metal surface for accentuation of gross structural details and defects for observation by
the unaided eye or at magnifications not exceeding ten diameters.
MACROGRAPH: A graphic reproduction of the surface of a prepared specimen at a magnification not exceeding ten
diameters. When photographed, the reproduction is known as a photomacrograph.
MACRO INSPECTION: Utilizes deep etch and examination under low magnification up to 10 diameters. It reveals
flow lines, etc.