Effect of Amplitude on Wave Propagation

Abstract

It is common to use ultrasonic techniques to measure elastic properties of the porous media. However, conventional methods are unable to measure local strain in ultrasonic wave. This is not clear how the velocity of wave depends on its amplitude. In this work we, 1) measured the particle displacement in the ultrasonic wave using a Laser Doppler Interferometry (LDI) and 2) measured changes of P-wave velocities with wave amplitude for elastic (Aluminium), viscoelastic (Polymethylmethacrylate), and granular media (dried Gosford sandstone). We checked this phenomena using a conventional ultrasonic receiver and linked this changes to a local strain in wave. The study indicated that for a sandstone sample by increasing of local strain produced by an ultrasonic wave from 7*10-6 to 2*10-5 the P wave velocity increase by 0.7%. We also analysed the accuracy of velocity measured using LDI as a receiver and compare the results with that using conventional transducers. Moreover, the effect of proper couplant of the sample and the transducer was investigated in details.