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Stress evaluation method and apparatus therefor

  • US 5,557,048 A
  • Filed: 09/28/1994
  • Issued: 09/17/1996
  • Est. Priority Date: 09/28/1993
  • Status: Expired due to Fees
First Claim
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1. A stress evaluation method comprising the steps of:

  • propagating a longitudinal wave in a thickness direction at a non-loaded portion of a test piece to be tested;

    measuring a propagation time of the longitudinal wave in the test piece at the non-loaded portion upon reception of a reflection wave reflected in the thickness direction from a bottom surface of the test piece at the non-loaded portion;

    propagating a longitudinal wave and a shear wave in a thickness direction at a loaded portion of the test piece;

    measuring a respective propagation time of said longitudinal wave and said shear wave in said test piece at the loaded portion upon reception of a respective reflection wave reflected in the thickness direction from a bottom surface of said test piece at the loaded portion;

    calculating a thickness at said loaded portion using a longitudinal wave acoustic velocity at the non-loaded portion which is obtained from a ratio between a thickness at the non-loaded portion and the propagation time of the longitudinal wave at the non-loaded portion;

    calculating a shear wave acoustic velocity based on a relationship between said thickness at the loaded portion and said propagation time of said shear wave at said loaded portion; and

    evaluating a magnitude of an internal average stress in said thickness direction acting in said loaded portion based on said shear wave acoustic velocity and a predetermined relationship between shear wave acoustic velocities and corresponding stresses.

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