Near point-source longitudinal and transverse mode ultrasonic arrays for material characterization

Specially constructed near point-source ultrasonic transducers (0.75 MHz) were designed to preferentially stimulate and receive the one longitudinal (P) and two transverse (S) propagation modes. Arrays of these transducers were placed on a rectangular prism of common soda-lime glass, which served as an ideal homogeneous, isotropic medium, to evaluate the uncertainty of a newly developed phase velocity measurement method. Through the use of the Radon transform, the data were transformed from the offset-time (x-t) domain to the intercept time-horizontal slowness (/spl tau/-P) domain. From the shape of the curves in the /spl tau/-p domain, the phase velocity of the propagating waves may be determined for a range of directions. The phase velocities determined using this method were accurate for incidence angles up to 76/spl deg/, 64/spl deg/ and 77/spl deg/ for the P, SV, and SH wave modes, respectively. Phase velocities of 5724/spl plusmn/64, 3411/spl plusmn/30, and 3467/spl plusmn/15 m/s were determined for the P-wave, SV-wave, and SH-wave modes, respectively. This agrees with the direct transmission P-wave and S-wave velocities of 5690/spl plusmn/60 and 3440/spl plusmn/26 m/s, respectively, to better than 1%.