A noncontact technique has been developed for the remote interrogation of submerged and limited access metal containers for determining the presence of fluid inside, The technique is based on the damping effect of water on the thickness mode resonance of the container wall. A transmitter-receiver pair of piezoelectric transducers is placed at a standoff distance of 5 mm from the container wall with the water outside the container providing ultrasonic coupling medium. The excitation frequency applied to the transmitter is swept between 0.8-4.0M Hz and the receiver transducer detects the signal, in the form of a frequency spectrum, returned from the wall. By analyzing the variation in the observed spectrum, it is straightforward to determine whether the container is fluid or air backed thereby detecting if the container has leaked.

Apparatus and method for non-contact (stand-off) ultrasonic determination of certain characteristics of fluids in containers or pipes are described. A combination of swept frequency acoustic interferometry (SFAI), wide-bandwidth, air-coupled acoustic transducers, narrowband frequency data acquisition, and data conversion from the frequency domain to the time domain, if required, permits meaningful information to be extracted from such fluids.

A swept-frequency ultrasonic interferometry technique is used for noninvasively determining acoustic properties of fluids inside containers. Measurements over a frequency range 1-15 MHz on six liquid chemicals are presented. Measurements were made with the liquid inside standard rectangular optical glass cells and stainless steel cylindrical shells. A theoretical model based on one-dimensional planar acoustic wave propagation through multi-layered media is employed for the interpretation of the observed resonance (interference) spectrum. Two analytical methods, derived from the transmission model are used for determination of sound speed, sound attenuation coefficient, and density of liquids from the relative amplitude and half-power peak width of the observed resonance peaks. Effects of the container material and geometrical properties, path-length, wall thickness are also studied. This study shows that the interferometry technique and the experimental method developed are capable of accurate determination of sound speed, sound attenuation, and density in fluids completely noninvasively. It is a capable and versatile fluid characterization technique and has many potential NDE applications.

Experiments were undertaken to investigate the feasibility of using propagating ultrasonic waves to find the speed of sound and density of solutions contained in opaque, sealed containers. A portable design is proposed which consists of 3 ultrasonic transducers aligned on a single plane along the surface of a tank. The content is then examined by measuring the time it takes for a signal to reflect off the back wall of the tank and return to another transducer. This time domain response approach delivered a very accurate analysis, with a low spread of results. This report demonstrates that by using this technique, very small changes in density can be observed. The final error in the density has been found to be less than 2%, which is adequate to reliably tell the difference between salt and fresh water.

An apparatus for noninvasively monitoring the flow and/or the composition of a flowing liquid using ultrasound is described. The position of the resonance peaks for a fluid excited by a swept-frequency ultrasonic signal have been found to change frequency both in response to a change in composition and in response to a change in the flow velocity thereof. Additionally, the distance between successive resonance peaks does not change as a function of flow, but rather in response to a change in composition. Thus, a measurement of both parameters (resonance position and resonance spacing), once calibrated, permits the simultaneous determination of flow rate and composition using the apparatus and method of the present invention.

This thesis presents a novel ultrasonic instrument for non-invasive and in-situ characterization of journal bearing lubricant viscosity. In particular, the application to journal bearings is described by non-invasively measuring the viscosity and localized power losses throughout operation. This ultrasonic viscometer is based on the reflection of polarized shear waves from a thin resonating coating layer to increase the measurement sensitivity, in comparison to conventional ultrasonic methods. This instrument allows for a full engine oil viscoelastic characterization in-situ. The book investigates the effects of temperature, pressure and shear rate, and describes in detail the ultrasonic setup and method. Further, it demonstrates that the same technique can be applied similarly to monitor the lubrication of other engine components. As such, it offers a unique instrument that can drive the research of oil formulations to improve engine performance and fulfill the requirements of international fuel economy regulations.