Abstract

Stroboscopic Pulse Method of Nonlinear Parameters Measurements

V.Kazakov (Institute of Applied Physics RAS, Nizhny Novgorod, Russia)

e-mail: kazak@appl.sci-nnov.ru

A new stroboscopic method of nonlinear parameters measurement is presented. The method is based on application of ultrasonic pulses and low frequency vibration to the sample. The high frequency ultrasonic pulse time of flight is measured in different phases of the low frequency vibration. Synchronization of the ultrasonic pulses with the phase of the low frequency vibration allows determination of the sound speed for different level of the low frequency strain. The dependence of sound speed on applied stress is used for nonlinear parameter calculation. The experiment was conducted in a sandstone bar with the ultrasonic pulse, frequency 6 MHz, propagating across the bar and the low-frequency vibration excited along the bar. The low frequency vibration was varied from 1 to 10 kHz. Experiments conducted in sandstone show the nonlinear parameter was in the range 4000-8000 and slightly dependent on the vibration frequency. We find the stress as a function of strain by integrating the measured sound speed as a function of strain.

Section : 3