Prediction of the S–N curves of high-strength steels in the very high cycle fatigue regime

Fatigue Strength Prediction Formulae for Steels and Alloys in the Gigacycle Regime

“…Equations (1) and (2) are based on Murakami's research [6], [9], conducted in the high cycle regime at 10 7 cycles [1], [10]. Therefore, replacing σ a with σ w at 10 7 cycles in (2) should give a value for area that causes the fatigue failure at 10 7 cycles.…”

“…In (4), σ w is in MPa, Hv is in kgf/mm 2 , and area is in μm. The main limitation of this model is that it is valid only for the high cycle regime for 10 7 cycles [10]. The main difficulty of using this model is that it requires a prior prediction of the location of the inclusion or defect that causes the damage in the future.…”

“…10 7 cycles [1]. Structural parts such as connecting rods, crank shafts and helical springs experience more than 10 10 cycles in their service lives [2].…”

“…Railway and offshore structures generally exceed 10 8 cycles [3]. Most of the fatigue design codes [4] too provide stress life S-N curves up to 10 9 cycles for designing elements in steel structures such as bridges. However, in designs, a fictive fatigue limit is often assumed at the end of the high cycle regime [2], [4].…”

“…The main parameters of these models are the size of defect or inclusion ( area ) and Vickers hardness (Hv) [6], [9]. Liu et al [1], [10], Wang et al [4], Mayor et al [8], [11] and Chapetti et al [12] have all proposed modifications to Murakami's model in order to widen its applicability in the gigacycle regime.…”