P4H-1 Finite Amplitude Method for Measurement of Nonlinearity Parameter B/A Using Plane-Wave Tone Bursts

Several finite amplitude approaches have been used to determine the nonlinearity parameter B/A of different materials. However, diffraction corrections or measurements far from the transmitting transducer are necessary to comply with the plane wave assumption inherent in the classical method. Alternatively, broadband, absolute pressure measurements in combination with theoretical nonlinear field calculations must be performed. In this study a measurement technique is proposed that eliminates the need for any of these steps. The technique is a variation of the finite amplitude insert substitution (FAIS) method. An 8 cm diameter, 2.25 MHz transmitting transducer was used to generate sinusoidal tone burst pulses, and the second harmonic amplitude was measured with and without the unknown sample in the beam per the FAIS method. Measurements were made near the transmitting transducer face where the field is reasonably plane until the diffracted wave from the transducer edge arrives, so a diffraction correction was not necessary. Results for two materials, glycerol and corn oil, were within 10% of published values for B/A.