Technique for applying direct resistance heating current to a specific location in a specimen under test while substantially reducing thermal gradients in the specimen gauge length

Abstract

A technique for imparting direct resistance heating to a gauge length of a conductive metallic specimen under test and which can be used to add an independent dynamic thermal capability to a mechanical material test system. Specifically, a pair of, e.g., conductive collars, each of which encircles and abuts against a corresponding portion of the external surface of the specimen near an opposing end of its gauge length and inward of a corresponding grip. Each collar imparts additional self-resistive heat to the specimen along a circumferential collar/specimen interface. This additional heat appreciably reduces or cancels thermal gradients otherwise arising from self-resistive heating across the gauge length as well as compensates for thermal losses in each specimen end section. Through this arrangement, each specimen end section and the grips are not appreciably heated as the gauge length heats. The amount of additional heat is set by selecting a collar material to have a desired resistivity and also by appropriately dimensioning each collar.