Local surface elastic constants by resonant-ultrasound microscopy

Abstract

We report a method—resonant-ultrasound microscopy—for measuring elastic-constant distribution over a solid’s surface. Applying an oscillating electric field to a rectangular-parallelepiped oscillator of langasite (La3Ga5SiO14) crystal by a surrounding solenoid coil, we generated and detected vibrations of the crystal without electrodes and without wires. Acoustic coupling of the specimen to the oscillator is only made at an antinodal vibration point on the crystal’s bottom surface. The crystal’s resonance-frequency shift reflects elastic constants of the specimen in the contacting area. Point-contact measurement permits sensitive, quantitative evaluation of a material’s local elastic constants. As an illustrating example, we measured the elastic-stiffness distribution of a Nb–Ti/Cu resin superconductive wire. We compared our measurements with both static-contact and dynamic-contact models.