EDDY-CURRENT DECAY AND RESISTIVITY MEASUREMENTS ON LONGITUDINALLY GROOVED HIGH-PURITY ALUMINUM BARS

The eddy current decay (ECD) method for determining electrical resisti vity uses a relationship between the time constant of magnetic flux di ffusion and resistivity. This method is shown to be valid for determin ing the resistivity of solid high-purity aluminum cylinders with eight equally spaced longitudinal grooves machined into the surface. The ef fects of changes in groove dimensions for a 25.4-mm-diameter, supercon ducting magnetic energy storage (SMES) conductor stabilizer are report ed. Observations of machining, heat treatment, and material inhomogene ity effects are discussed. It is found that the ECD time constant is d ependent primarily on groove depth and that groove width has only a mi nor influence. An empirical equation relating groove dimensions with t he time constant and with resistivity is presented.