Accession Number : ADA119817

Title :   Effect of Nonparallelism on the Measurement of Ultrasonic Attenuation in Solids.

Descriptive Note : Interim rept.,


Personal Author(s) : Boudreault,Joseph Pierre Serge

PDF Url : ADA119817

Report Date : Sep 1982

Pagination or Media Count : 117

Abstract : Evaluation of attenuation of ultrasonic waves in solids from pulse echo trains can be complicated by a number of factors. In this report one considers the effects of diffraction and nonparallelism of the sample surfaces in the linear approximation. A mathematical model for correcting the echo height for the effect of a wedge-shaped sample is constructed. By using a unique coordinate system, the path of a multiply-reflected ultrasonic wave is transformed into an equivalent unidirectional path. A diffraction correction then is applied by numerically integrating an improved version of the farfield solution to the diffraction integral. This model is used to interpret data taken on a steel plate which has different facets ground over a range of angles between 0 and 0.01175 radians. Plots are given of corrected attenuation measurements made with circular piezoelectric transducers having resonance frequencies between 3 and 7 MHz. A comparison is made between the present model and that of Truell and Oates (J. Acoust. Soc. Am. 35, 1382 (1963)), which was intended as an indicator of the necessity for applying a correction for nonparallelism. The present model corrects the first four echoes for frequencies f 6 MHz and angles gamma or = 4 x 10 to the minus 3rd power radians.

Descriptors :   *Wave propagation, *Ultrasonic radiation, Solids, Attenuation, Diffraction analysis, Fresnel zones, Pulse trains, Corrections, Echoes, Amplitude, Theses

Subject Categories : Acoustics
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE