High Stress

Abstract

High-low type two step fatigue tests were carried out at a stress ratio of-1.0 with a fine-grained isotropic nuclear graphite IG-110, for which the cumulative fatigue damage was evaluated. The following conclusions were derived: (1) Cumulative fatigue damage was enhanced with decreasing the first cycle ratio and the stress level. (2) The regeneration of stress history was observed at the first stress ratio of 0.1. (3) Cumulative fatigue damage for first cycle ratios in excess of 0.3 can be described by the linear cumulative fatigue damage rule, whereas the ratios less than 0.3 result in a cosiderable deviation from the linear rule.