A 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

摘要

A technique for imparting direct resistance heating to a gauge length of a conductive metallic specimen (100, 200) 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 (203, 203A) , 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 (214, 214A) . 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 (201, 201A) . 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 .