The Effect of Varying Stress on the Fatigue Strength of the High Strength Steel

Abstract

With a view to studying on the effect of varying stress on the fatigue strength of the high strength steel, the multiple repeated rotating, or plane bending fatigue tests were carried out at two stress levels on three high strength steels, which were S15CK tufftrided steel, SCM4 induction hardened steel, and l% Cr-Moquenched and tempered steel taken from the main gear for marine propulsion turbine. The results obtained are summarized as follows; (1) On the S15CK tufftrided steel, the fairly low stress under the fatigue limit is affected considerably the fatigue life, in case of σ_1=45kg/mm^2, n_l/N_l=0.03 (n_l/n_2=2×10^4/5×10^6). (2) On the SCM4 induction hardened steel, the understress till 0.5 σ_ω (σ_ω; fatigue limit) is affected the fatigue life, in case of σ_1=80kg/mm^2, n_l/N_l=0.1 (n_l/n_2=5×10^3/5×10^6). (3) On the l% Cr-Mo quenched and tempered steel, the fairly low stress under the fatigue limit is affected considerably the fatigue life, in case of σ_1=50kg/mm^2, n_l/N_l=0.1 (n_l/n_2=8×10^3/5×10^6), 0.05 (n_l/n_2=4×10^3/5×10^6).