Benchtop magnetostriction measurements

Strains of magnetostrictive origin cause dynamic variations in the radial dimensions of a thin wall cylindrical ring during brief bursts of current through a coaxial conductor. Flux closure within the ring avoids demagnetizing effects while the brief duration of current flow allows for compact power sources and limits thermal drift. Changes in ring radius alter the air gap affecting the frequency determining capacitance in an oscillator circuit. Linearity with frequency allows the strain to be determined by demodulating the oscillator signal. Information relating to magnetostriction coefficients and dominant anisotropies are readily extracted from current vs strain plots. The simple apparatus and readily prepared samples facilitate rapid assessment of these properties in commercial steel alloys