The schoch effect to distinguish between different liquids in closed containers.

In different industrial branches, it is necessary to characterize liquids in closed containers. For small cans, accessibility to both sides is almost trivial. However, in industries in which larger containers are used, and especially in the dock industry, only one side is accessible practically; and damping often prevents through-transmission ultrasonic measurements or pulse echo techniques. It is known that built-in sensors can be used to determine density and wave velocity of liquids; but normally containers are not equipped with such sensors. It is also known that differences in the reflection coefficient at a solid-liquid interface can determine the density and sound velocity of liquids, but only if the difference in acoustical impedance between the solid and the liquid is small. For most containers this condition is not provided; therefore, a more sensitive method is needed. This paper reports simulations that show how identical containers, having different liquids inside, can be distinguished from one another by means of differences in the Schoch effect at a Lamb wave angle of incidence for harmonic-bounded ultrasonic beams.