引張強さをそろえた合金鋼SCM435およびSCr440調質材の疲労挙動

抄録

For estimating the fatigue strength of members, the value of static tensile strength σ_B is widely used as a parameter. However, when the values ofσ_B in different types of steels are equalized, their fatigue strengths are different from each other in general. In this study, in order to examine the phyisical background of the difference in fatigue strengths, using the heat-treated low alloy steels SCM 435 and SCr 440 whose tensile strengths are nearly equal, the rotating bending fatigue tests were carried out. Results show that the difference in crack initiation life of both materials is hardly observed, however the crack growth rate of SCM 435 is smaller than SCr 440. This difference in crack propagation can be evaluated by the crack growth law : dl/dN=σ_B C3(σ_a/σ_B)ⁿl.