Abstract
Fatigue tests were carried out on two kinds of high strength steel and three kinds of surface hardened steel under constant and variable stress amplitudes. The results obtained are summarized as follows;
(1) On the 1%Cr-Mo steel the completely reversed variable stress amplitude test gives a shorter fatigue life than that estimated from the modified Miner's S-N diagram, but the completely tension variable stress amplitude test gives a longer life.
(2) On the SNCM8 steel the second stress of no less than 40% of the fatigue limit affects the fatigue life under variable stress amplitude.
(3) The fatigue behavior of the tufftrided steel changes depending on the kinds of materials or the dimension of specimens under variable stress amplitude.
(4) On the SCM4 induction hardened or SNC21 carburized steel the scatter of the fatigue lives is large under constant stress amplitude, but their fatigue lives are longer under variable stress amplitude than those estimated from the modified Miner's S-N diagram.
