Measurement of Plane Stress States using Electromagnetic-Acoustic Transducers

  • A. V. Clark
  • S. R. Schaps
Chapter

Abstract

Assessment of structural safety requires knowledge of the shape of any defect and the stresses acting on it. Ultrasonics can be used to measure applied stress since there is a (small) change in velocity with stress. However the problem becomes more difficult when measuring residual stress. Here the influence of other factors such as variation in microstructure must be accounted for. For example, one method is to measure the percent difference in velocity of orthogonally polarized shear waves (the acoustic birefringence B). When the material symmetry and stress axes coincide [1],
$$B = B_o + C_a D$$
(1)
where Be is the birefringence in the unstressed state, Ca is the acoustoelastic constant and D is the difference of principal stresses. The usual procedure is to measure B at a “reference” location where stresses are known, and assume homogeneity of microstructure.

Keywords

Welding Boulder EMAT 

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References

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Copyright information

© Plenum Press, New York 1995

Authors and Affiliations

  • A. V. Clark
    • 1
  • S. R. Schaps
    • 1
  1. 1.Materials Reliability DivisionNational Institute of Standards and TechnologyBoulderUSA

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