Volume 104, Issue 1, July 1998
Index of content:
- ULTRASONICS, QUANTUM ACOUSTICS, AND PHYSICAL EFFECTS OF SOUND 
104(1998); http://dx.doi.org/10.1121/1.423266View Description Hide Description
A simple and noncomputational intensive method is proposed for elastically characterizing an isotropic material. The Poisson’s ratio and the shear modulus are determined from the axisymmetric vibrations of a cylinder with a length equal to its diameter. These vibrations are excited by means of a wide spectrum impact. The optical system used allows the simultaneous detection of several vibration modes. The out-of-plane displacement is detected by speckle interferometry. From the resulting vibration displacement spectrum, the two lowest frequencies are obtained, both corresponding to axisymmetric modes—specifically, the first symmetric mode and the first antisymmetric mode. The values of both dynamic elastic constants are obtained by comparing previously computed nondimensional natural frequencies and the measured frequencies. The method requires only one experiment and needs no electronic computation. The results obtained for an aluminum cylinder are coherent and confirm the appropriateness of the method. The relative difference between the Young’s modulus values calculated by the proposed method and applying the elementary theory to a long rod of the same material is 0.27%. Comparing the shear modulus value obtained by this method and the calculated one from the lower frequency in torsion, a relative difference of 4.6% is found.
Examination of the two-dimensional pupil function in coherent scanning microscopes using spherical particles104(1998); http://dx.doi.org/10.1121/1.423268View Description Hide Description
The determination of the modulus of the pupil function in reflection acoustic and optical microscopy with the help of spherical particles is demonstrated. The theoretical examination shows that this method can give good results if the pupil function drops smoothly towards the edge. For a pupil with a sharp edge this technique can give the accurate pupil function only by imaging large spheres. The dependence of the accuracy of the method on the size of the spherical particle is analyzed. Numerical and experimental results obtained for the confocal scanning optical microscope and the scanning acoustic microscope are examined.