Dispersion in acoustics variation of wave velocity

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dispersion: In acoustics, variation of wave velocity with frequency. 7 E event: See acoustic emission event. event counting: Measurement of the number of acoustic emission events. event rate: Number of acoustic emission events detected in a specified unit of time. F false indication: See indication, false. felicity effect: Appearance of significant acoustic emission at a load (or pressure) level below the previous maximum applied. 5 felicity ratio: Measurement of the felicity effect. Defined as the ratio between (1) the applied load (or pressure) at which acoustic emission reappears during the next application of loading and (2) the previous maximum applied load. 5 filter: (1) Electrical circuit that leaves a signal unaffected over a prescribed range of frequencies and attenuates signal components at all other frequencies. 10,19 (2) Data analysis process for reducing data files. finite element analysis: Numerical technique for the analysis of a continuous system whereby that system is decomposed into a collection of finite sized elements. 10 flaw: Rejectable or unintentional anomaly or imperfection. See also defect and discontinuity. 10 429 Acoustic Emission Testing Glossary
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G general examination: In personnel qualification, a test or examination of a person’s knowledge, typically (in the case of nondestructive test personnel qualification) a written test on the basic principles of a nondestructive test method and general knowledge of basic equipment used in that method. (According to ASNT’s guidelines, the general examination should not address knowledge of specific equipment, codes, standards and procedures pertaining to a particular application.) 10 grinding crack: Shallow crack formed in the surface of relatively hard materials because of grinding heat. Grinding cracks typically are 90 degrees to the direction of grinding. 10 H hardness: Resistance of metal to denting, to plastic deformation by bending or to mechanical deformation by scratching, abrasion or cutting. Typically measured by indentation. heat affected zone: Base metal that was not melted during brazing, cutting or welding but whose microstructure and physical properties were altered by the heat. 10 hertz (Hz): Measurement unit of frequency, equivalent to one cycle per second. 10,16 hit: See acoustic emission hit. hit lockout time: Time interval set to suppress late arriving parts of an acoustic emission signal. hsu-nielsen source: See pencil break source . I indication: Nondestructive test equipment response to a discontinuity, requiring interpretation to determine its relevance. Compare crack; defect; discontinuity; false indication. 10 indication, discontinuity: Visible evidence of a material discontinuity. Subsequent interpretation is required to determine the indication’s significance. 10 indication, false: Test indication that originates where no discontinuity exists in the test object. Compare defect and indication, nonrelevant. 10 indication, nonrelevant: Indication due to misapplied or improper testing.
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  • Fall '19
  • Nondestructive testing, Acoustic Emission

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