A Simplified Test Device for Thermal-stress Ratcheting (a Three Bars Specimen) and Some Results

Abstract

A special plate-shaped specimen with two symmetrical, straight air gaps in the center portion and a pair of holes for load chucks at the end is proposed, fabricated and examined for thermal-stress ratcheting. Effective portion of the specimen is divided into three bars by a couple of slender air gaps. Two side bars out of three are enveloped with special trace heaters. Testing is made by on-off cycling of the heaters under a constant steady membrane stress. When thermal loading is applied by heating, the middle bar becomes a cold element and the other side bars hot elements. Descriptions and characteristics of the specimen, the test procedures and typical results are presented.