Abstract
Ni-Cr-Mo steel were tested axially under completely reversed constant strain range and completely reversed constant stress range from monotonic tension to 130 cycles. Hysteresis loops were recorded at intervals throughout the life to failure. The mechanism of tests were explained by true stress considering the change of test section. That is, completely reversed straining test was completely reversed as to true stress. The completely reversed stressing test was partially reversed as to true stress, and then the mean stress caused the increase of mean strain. Stress and strain cycling results were compared on the basis of the condition for the first cycle. For the same condition for the first cycle, cyclic stressing test shows relatively shorter life than cyclic straining test. The mechanism of fracture were found a conventional fatigue during cyclic straining but a necked-out type with the increase of mean strain during cyclic stressing. The total plastic strain to failure of cyclic straining test was larger than that of the cyclic stressing test. This seems to show the difference of modes of fracture of the tests.
