Investigation of Acoustic Fields Generated by Eddy Currents Using an Atomic Force Microscope (Postprint)

This paper reports the experimental measurement and imaging of the acoustic fields generated by low-frequency eddy currents in metals in the absence of an external static magnetic field using a modified atomic force microscope. Acoustic displacements in a typical metal placed in eddy current field without static magnetic field were theoretically computed and found to be in the range of few hundred picometers. A modified atomic force microscope was used to detect and measure the acoustic displacements in a single crystal copper. The setup was also used to image acoustic fields in a titanium alloy sample. Details of the modified AFM to measure and image acoustic displacements are presented. The role of electrical and elastic properties on the contrast in acoustic images of Ti-6Al-4V sample is discussed.