Wave conversion

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As a wave conversion , or mode conversion ( English mode conversion ) is defined as the splitting of an incident wave at a boundary surface in other modes ( modes ).

Oblique incidence of a longitudinal wave at an interface between two solids. An incident longitudinal wave Pi (“P” for pressure wave ) is partially reflected and transmitted as a shear wave (PSr) and pressure wave (PPr) (PSt and PPt). The nomenclature is as follows: The first letter stands for the wave type of the causative wave (primary wave) and the second letter for the type of secondary waves that have arisen after the mode conversion.

If a longitudinal structure-borne sound wave from a fluid (e.g. water or air ) hits a solid (e.g. steel plate ), it is broken according to Snell's law of refraction , but a second broken transverse wave also arises in the solid. This means that the incident wave is split into two different wave types at the interface. If you look at a wave that strikes an interface between two different solid bodies (e.g. aluminum and steel), the wave type of the reflected wave is also split. See the illustration opposite.

In addition to these simple mode conversions, an incident wave can also be converted into surface waves. For example, if a longitudinal wave is radiated onto a boundary surface at a shallower angle than that of total reflection , this is indeed totally reflected, but a surface wave that runs along the boundary layer is also generated. The incident wave is converted into reflected longitudinal and surface waves.

In general, mode conversions are not discrete processes; H. some of the incident energy is converted into different types of waves. The amplitudes ( transmission factor , reflection factor ) of the converted waves depend on the angle of incidence.

For example, shaft conversion probes are used for the non-destructive testing of pipes .

literature

  • Karl F. Graff: Wave Motion in Elastic Solids . Courier Dover Publications, 1975, ISBN 0-486-13957-3 , pp. 394 ff . ( limited preview in Google Book search).
  • Volker Deutsch, Michael Platte, Manfred Vogt: Ultrasonic testing: Basics and industrial applications . Springer DE, 1997, ISBN 3-642-59138-8 , pp. 86 ff . ( limited preview in Google Book search).
  • Josef Krautkrämer, Herbert Krautkrämer: Materials testing with ultrasound . Springer-Verlag, 1975, ISBN 0-387-06901-1 .

Individual evidence

  1. ↑ Gang Chen Department of Mechanical Engineering MIT: Nanoscale Energy Transport and Conversion: A Parallel Treatment of Electrons, Molecules, Phonons, and Photons: A Parallel Treatment of Electrons, Molecules, Phonons, and Photons . Oxford University Press, 2005, ISBN 0-19-977468-4 , pp. 178 ff . ( limited preview in Google Book search).
  2. ^ Joseph L. Rose: Ultrasonic Waves in Solid Media . Cambridge University Press, 2004, ISBN 0-521-54889-6 , pp. 54 ff . ( limited preview in Google Book search).
  3. ↑ Sigrun Hirsekorn: Ultrasonic testing of austenitic cladding, mixed seams and austenitic weld seams: Theory - Practice - Regulations . expert verlag, 1995, ISBN 3-8169-1078-5 , p. 189 ff . ( limited preview in Google Book search). , especially chapter 4 also on Rudi Schmid: Problem-oriented test concepts for austenitic welded and mixed welded joints. Retrieved July 14, 2013 .