NDT Glossary

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• B-scan - A data presentation method applied to pulse echo techniques. It produces a two-dimensional view of a cross-sectional plane through the test object. The horizontal sweep is proportional to the distance along the test object and the vertical sweep is proportional to depth, showing the front and back surfaces and discontinuities between.
  
• Back Reflection - The signal received from the far boundary or back surface of a test object.
  
• Background - The visual, radiographic or electronic response against which an indication from a discontinuity must be viewed.
  
• Background fluorescence - Fluorescent residues observed over the general surface of the part during fluorescent penetrant inspection.
  
• Background Noise - The extraneous signals caused by random signal sources within or exterior to the ultrasonic testing system, including the test material. Sometimes called grass or hash.
  
• Background Radiation - The radiation of man's natural environment, consisting of that which comes from cosmic rays, the naturally radioactive elements of the earth and the impact of the cumulative deposition from stratospheric fallout and nuclear accidents such as Chernobyl. Term may also mean radiation extraneous to an experiment.
  
• Back Scatter - Scattered signals that are directed back to the transmitter/receiver.
  
• Bainite - An intermediate transformation product from austenite in the heat treatment of steel. Bainite can somewhat resemble pearlite or martensite, depending on the transformation temperature.
  
• Banking Concept - An idea or model used to facilitate the explanation of radiation exposure permitted in a lifetime.
  
• Baseline - The reference line in a measurement by triangulation. (I.e. The horizontal trace across the A-scan display. It represents time and is generally related to material distance or thickness.)
  
• Beachmarks - Macroscopic lines on a fatigue fracture that show the location of the tip of the fatigue crack at some point in time. Must not be confused with striations, which are extremely small and are formed in a different way.
  
• Beam Alignment Measurements - Measurements that provide data on the degree of alignment between the sound beam axis and the transducer housing. This information is particularly useful in applications that require a high degree of certainty regarding beam positioning with respect to a mechanical reference surface
  
• Beam Exit Point - See probe index.
  
• Beam Profiles - A measurement of the intensity of the beam across its width (or profile). It provides valuable information about transducer sound field characteristics. Transverse beam profiles are created by scanning the transducer across a target (usually either a steel ball or rod) at a given distance from the transducer face and are used to determine focal spot size and beam symmetry. Axial beam profiles are created by recording the pulse-echo amplitude of the sound field as a function of distance from the transducer face and provide data on depth of field and focal length.
  
• Beam Spread - The divergence of the sound beam as it travels through a medium. Specifically, the solid angle that contains the main lobe of the beam in the far field.
• Beer's Law -the ability of a penetrant to yield an indication depends primarily on its ability to fluoresce as a very thin film. The performance of penetrants based on the physical constraints of the dyes can be predicted using Beer's Law equation. This equation does not hold true when very thin layers are involved but works well to establish general relationships between variables.
  
• Bequerel, Henri - The discoverer of naturally occurring radioactive uranium in 1896. He showed how these particles differed from the recently discovered x-ray radiation by showing that they could be deflected by an electric or magnetic field.
• Betatron - A particle accelerator that is used to accelerate electrons (beta particles) and collide them with a target to produce high energy radiation.
• Beta Radiation - A high speed electron, small in mass, moderate penetrating abilities (e.g. unable to penetrate more than a few millimeters of biological tissue).
  
• Black-light - See ultraviolet light.
  
• Bottom Echo - See back reflection.
  
• Boundary - The edge, end or face of a finite medium.
  
• Boundary Echo - Reflection of an ultrasonic wave from an interface.
  
• Bremsstrahlung - A German term that means "braking rays." It is an important phenomenon in the generation of X-rays. In this process, a high speed electron traveling in a material is slowed or completely stopped by the forces of any atom it encounters.
  
• Brittle Rupture - A material failure mechanism that results with little or no plastic (permanent) deformation prior to fracture.
  
• Broad Banded - Having a relatively wide frequency band width. Used to describe pulses that display a wide frequency spectrum and receivers capable of amplifying them. Opposite of narrow banded or tuned.
  
• Bubbler - See water column.
  

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