Arrival times of scattered ultrasonic signals from a solid inclusion in an elastic material

Measurements are reported of the arrival times of broadband ultrasonic pulses scattered by a circular, cylindrical, solid inclusion imbedded in a matrix whose longitudinal wave speed is lower than that of the scatterer. The wavenumber‐inclusion radius product ka, ranges from approximately 1 to 15. The matrix materials are water, polyester, and brass; and the inclusion materials are copper, quartz, stainless steel, and tungsten. A strong, scattered pulse, corresponding to a circumferential wave on the cylinder is observed for c_s≳c_P, where c_s is the shear wave speed of the inclusion material and c_P is the longitudinal wave speed of the matrix material. These observations are in agreement with results published by others. The experiments also show that the pulse corresponding to the circumferential wave is not observed for c_s<c_P. It is shown how the approximate diameter and longitudinal wave speed of the inclusion can be determined from measurement of the arrival times of the scattered pulses.