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Theoretical development for reflection effects for a bounded ultrasonic beam from flat interfaces and plates. Experimental observations for reflection from thick solid plates.

Acoustooptic interaction theory is applied to ultrasonic pulses in order to determine pulse parameters from the light diffraction pattern produced by the pulses. Experiments are described to show how pulse shapes change when propagation is in a nonlinear liquid. It is shown that pure electronic determinations of pulse shapes do not describe all the changes accurately whenever the probe response is not known exactly. Use of present method is able to eliminate this problem. Examples of pulse propagation as investigated by acoustooptic method are given and evaluated. Keywords: Ultrasonic pulses; Acoustooptics; Nonlinearities reflection.

Four aspects of ultrasonic reflectivity are discussed; reflection coefficient reducibility from thin plate to halfspace; reflection of bounded beam; inhomogeneities of reflector; and multifrequency beam reflection phenomena. (Author)

A general description is given of the ultrasonic nonspecular reflection and transmission effects for layered media. This description forms the basis for evaluation, via acoustooptic interaction techniques to measure reflectivity from solid plates in a liquid and also for the detection of local inhomogeneities of the plate. (Author)

Theoretical and experimental evidence is given to explain reflectivity and transmissivity of bounded ultrasonic beams impinging on flat solid thin and thick plates immersed in water. Effects are described which have to be considered when high amplitude ultrasonics is used or when the liquid-solid combination differs significantly from the usual metal-water combination of reflecting media. (Author)

The work describes the mathematical background and the physical principles which were used to perform calculations of sonic reflectivity from the water side of a water-ice-air layered system where the angle of incidence is varied to produce changes of the magnitude and the phase of the incident sonic beam as it is reflected from the ice. It is shown that evaluation of these changes in reflectivity can be used to determine the thickness of the ice without having to be in direct mechanical contact with the ice. The computation of modulus and phase of the reflected beam is accomplished via a modified Simplex Computation Method. The basic concepts of the method are described, as are the modifications incorporated to make the program useful for calculations of ice thicknesses which one would ordinarily expect to encounter in the Artic Ocean. The report contains the description of a computer program to calculate the mode structure of an ice plate floating on water. Reflectivity of sonic signals which set up the modes is used to determine the thickness of the reflecting ice plate., See also Rept. no. GUUS-04799 dated 24 Apr 79, AD-A068 195. Master's thesis.

A numerical integration method is developed for calculating the changes in beam profile and amplitude upon reflection of a bounded ultrasonic beam incident on a liquid-solid flat interface at the longitudinal wave critical angle and the Rayleigh angle. No approximations, valid only at the Rayleigh angle, are used, and the method is applicable to all angles of incidence. (Author)

The report contains a collection of titles and abstracts of papers published and under consideration, relative to reflectivity from ice cover.

The work sponsored by this Contract was concerned with a scale-model study of sonic reflectivity, transmissivity and the partition of energy upon sonic incidence at the Arctic Ice cover. The basic experimentation was accomplished by using megahertz ultrasonic signals and allowing them to impinge, in a controlled manner, on various liquid/solid boundaries, simulating as much as feasible the actual situation which is found in the Arctic. From the results of the measurements of reflectivity and mode conversions on scale-model samples, a number of properties of both the liquid and the solid were deduced., See also report dated 12 Sep 73, AD-766 485.

A summary report listing tasks performed and complete reference listing of all publications originating from Contract during reporting period. The main emphasis was placed on reflection and transmission of a bounded ultrasonic beam since it had been found that plane wave theory (as almost always used in the past) does not explain the existence of nonspecular ultrasonic reflection from interfaces, where 'nonspecular reflection' refers to beam displacements, beam split-up, intensity distribution changes within the reflected beam, and other similar phenomena. Such nonspecular reflections occur for simple liquid-solid interfaces when the incident beam impinges at the Rayleigh angle and, for solid plates immersed in a liquid, at Lamb mode angles.

Reflectivity curves are calculated for sea-ice/water boundaries in which the densities and sonic velocities in the two media are changed in increments. The resulting changes in the reflectivity curves are interpreted in terms of the influence of the parameters. Analysis is given indicating under which conditions reflectivity measurements can or cannot yield information about the values of sonic velocities and densities of the sea-ice and the water. Possible misleading measurements are indicated and the influence of Rayleigh waves on measurement is described. (Author), Report on Scale Model Ultrasonic Study of Arctic Ice.

Results of earlier work and recent developments in the area of ultrasonic reflectivity at the Rayleigh angle on liquid-isotropic solid interfaces are compared in order to show which of the parameters are significant in relating ultrasonic surface waves to the observed beam displacement. An extension is made to include water-single crystal copper interfaces to measure generalized and pseudo surface waves. Some phase measurements of the reflected energy are obtained and an interpretation is given which differs from the existing theories describing ultrasonic reflectivity at the Rayleigh angle. (Author)

The generation of ultrasonic surface waves during beam reflection from liquid-solid interfaces is discussed. Conditions are given under which the surface wave is created on isotropic and anisotropic solids. Methods are described by which the amplitude, velocity and absorption of the surface wave can be measured using optical probes. Critical angle reflectivities and resulting crystal orientation possibilities are discussed. (Author)

Techniques for exciting ultrasonic surface waves and their advantages are described. Preferred methods for particular applications are given. Experimental correlation is made to theory for light scattering from surfaces excited with Rayleigh waves. Data are given for velocity and wave amplitude measurements obtained by light scattering. Use of light scattering is considered for investigating surface states, Rayleigh wave dispersion and absorption. (Author)

The light intensity distribution in the orders of a diffraction pattern produced by the interaction of progressive ultrasonic surface waves and a monochromatic light beam is calculated. From the diffracted light intensity one can determine the amplitude of the surface wave, and from the spacing of the diffraction orders one obtains the velocity of the surface wave. (Author)

The equations for the energy ratios of reflected and refracted to incident longitudinal ultrasonic waves are programmed for FORTRAN. The ratios are determined as a function of angle of incidence for liquid-solid, solid-liquid, solid-vacuum or solid-solid flat interfaces. No assumptions are required concerning densities and relative magnitudes of the various wave velocities. Energy ratios are also calculated for critical angles, if they exist. The entire program and comments are given. (Author), Rept. no The Propagation of High Amplitude Sound Waves.