抄録
In the previous paper, the authors reported on the effects of multiple cumulative stresses on carbon steels (0.07%C, 0.25%C and 0.47%C), using Ono's rotary bending tester and cantilever type rotary bending tester, and on the relations between the fatigue lives and the deflections of test pieces etc. during the fatigue tests.
In the present paper, we have clarified the fatigue lives, in detail, by gradually varying the cycle ratios of the primary stresses, making the primary stresses above the fatigue limits of virgin material, under double cumulative stresses. Consequently, we have got the following results:
(1) On the low carbon steels (as S 10 C), the fatigue lives are prolonged than those of virgin material whether the secondary stresses are higher or lower than the secondary stresses. And the effects of cycle ratios are most remarkable when the cycle ratios of the primary stresses are: n1/N1≈0.5-0.6
(2) On the high carbon steels (as S 50 C), the effects of the cycle ratios of the primary stresses are not so remarkable as in cases of the low carbon steels, and the fatigue lives become longer than those of the virgin materials only when the primary stresses are made below than the secondary stresses, and they become the longest when the cycle ratios of the primary stresses are: n1/N1≈0.7-0.9. The fatigue lives, however, show a striking tendency to become shorter than those of virgin materials when the primary stresses are higher than the secondary stresses, and they become the shortest when the cycle ratios of primary stresses are: n1/N1≈0.4-0.6.
