Principles of Emar for Spectral Response

  • Masahiko Hirao
  • Hirotsugu Ogi

Abstract

An easy way to understand the EMAR principle is to consider the through-thickness resonances of bulk waves (thickness oscillations). Consider that a transducer is placed on the surface of a plate of thickness d and excites an ultrasonic plane wave of single cycle propagating in the thickness direction, whose wavelength and period are λ and T, respectively. The pulse wave undergoes the repeated reflections at both free surfaces and is received by the same transducer each time it reaches the incident surface. In the case of λ<<d, the received signals will be observed as shown in Fig. 4.1(a). The horizontal axis in Fig. 4.1 is the time measured from the excitation, and the vertical axis is the wave amplitude. T 0 denotes the round-trip time through the thickness. The amplitude decays as the propagation path increases, depending on attenuation of the material.

Keywords

Intermediate Frequency Constructive Interference Bulk Wave Analog Multiplier Burst Signal 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media New York 2003

Authors and Affiliations

  • Masahiko Hirao
    • 1
  • Hirotsugu Ogi
    • 1
  1. 1.Osaka UniversityJapan

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