| Acoustic microscopy can be used for very localized measurements of the velocity and attenuation of surface acoustic waves (SAWs). The technique is based on ultrasonic interference phenomena which give rise to V(z) curves when the acoustic probe is defocused. Applications of the quantitative mode of line-focus acoustic microscopy for non-destructive evaluation are investigated in this dissertation.;First, a theoretical model for the V(z) curve is presented. The characteristic functions of the acoustic lens, which play a central role in the model, have been determined by taking into account the important features of the lens. The validity of the measurement model has been verified by comparing theoretical with experimental results for various kinds of specimens. Using the measurement model, the effect of surface roughness on the SAW velocity measured by line-focus acoustic microscope has been investigated. The calculated results are consistent with experimental data measured for specimens with different surface roughnesses.;Line-focus acoustic microscopy has then been used to determine the elastic constants of cubic-crystalline solids and thin films from the directional variation of the SAW velocities. The elastic constants have been determined by best fitting the calculated SAW velocities to the measured values over a range of directions. By using the attenuation coefficient of the SAWs measured by the acoustic microscope as additional information, a method is proposed to simultaneously determine the mass density and the elastic constants. Experimental results are presented.;The use of line-focus acoustic microscopy for stress measurement has also been studied. The acoustoelastic effect for SAWs has been demonstrated and certain calibration constants have been measured. A nonuniform stress field has been measured by combining the scanning mode and the localized velocity measurement of the line-focus acoustic microscope. Finally, a self-calibrating method which can determine a 2-D stress profile without a calibration test, is proposed, and corresponding experimental data have been compared with finite element results. |
