CRACK OPENING BEHAVIOR OF ARTIFICIAL GRAPHITE-ELECTRODES IN THERMAL-SHOCK TEST

Thermal Shock tests by arc-discharge heating were carried out on the notched disc specimens of artificial graphite electrodes, while monitoring the change of crack opening displacement (C.O.D.) with time by using a clip gage. The crack abruptly extended from the notch tip at a certain time and stayed at the arc spot in the center of the specimen. The slope-theta of the line connecting the origin and C.O.D. just after abrupt extension of the crack, could be determined on each electrode sample within the accuracy of +/- 10%, independent of notch size. The theta-value thus determined was proposed to be used as a parameter for evaluating the thermal shock resistance of graphite electrode materials and to be named as "thermal shock energy dispersion rate".