Statistical Duplex S-N Characteristics of High Carbon Chromium Bearing Steel in Rotating Bending in Very High Cycle Regime

摘要

Statistical fatigue tests in very high cycle regime were carried out for high carbon chromium bearing steel (JIS: SUJ2) in rotating bending as a common research project. Thus the duplex S-N characteristics consisting of different S-N curves for surface-induced fracture and interior-induced fracture were confirmed clearly. Only the surface-induced fracture took place at the high stress levels, whereas only interior-induced fracture occurred at the low stress levels. However, both fracture modes were observed at the medium levels of the applied stress, where the occurrence probabilities of the respective fracture modes p_1 and p_2 were controlled by the applied stress under the condition of p_1+p_2 = 1.rnFatigue life distribution for each fracture mode can be represented by Weibull distribution with three parameters a, b and c, which is called shape parameter, scale parameter and location parameter respectively. Thus, the fatigue life distribution function is provided by f(n) = 1-exp {-[_(n - c)/b] ~a}, in which Weibull three parameters can be estimated from experimental data. Based on the stress dependence of Weibull parameters a , b and c , and the occurrence probabilities p_1 and p_2, the fatigue life distribution can be analytically obtained by applying the concept of mixed-mode Weibull distribution. It was finally found that the