A probabilistic model on crack initiation modes of metallic materials in very high cycle fatigue

The Effect of Baking Heat Treatment on the Fatigue Strength and Life of Shot Peened 4340M Landing Gear Steel

“…This is thought to come from grain refinement due to the compressive residual stress effect caused by the surface plastic deformation by SP. Below the hardened depth of about 200 μm, the SP specimen did not show a big difference in the hardness distribution with the baking heat treated specimens, and this was because the hardness was kept by the baking heat treatment instead of decreasing [ 18 ]. Above the hardened depth of about 200 μm, the hardness of SP-B246 specimen generally showed the largest one.…”

“…However, when the inclusion was contained, the crack initiation started from the inclusion almost with the form of an internal crack. A fine granular area (FGA) was found and formed in the vicinity around the inclusion [ 18 , 19 , 20 ]. A typical fish eye could be observed on the fracture surface, which was initiated from the inclusion.…”

“…That is, it is best to use materials without any inclusions in order to increase the fatigue limit by the compressive residual stress effect formed by SP. However, if SP is performed when the material contains inclusions, the stress concentration is applied to the inclusions by SP resulting as a cause of the lowering fatigue limit [ 18 , 19 , 20 ]. However, as the stress applied to the inclusions by SP is relaxed through the baking heat treatment performed after SP, the stress concentration causing fatigue is relieved and the fatigue limit is not lowered.…”

Proposal of a Probabilistic Model on Rotating Bending Fatigue Property of a Bearing Steel in a Very High Cycle Regime

“…Although the horizontal line was also indicated from the point of N = 10 9 along the dotted S-N curve, further experimental reconfirmation would be required in order to make clear the appearance of the horizontal portion in the fracture mode by continuing fatigue tests, until further long life region. Typical examples of fracture surfaces in the respective fracture modes are shown in Figure 2, where (a) gives the SEM observation of the fracture surface in the surface-induced fracture mode and (b) is the fracture surface in the interior-induced fracture mode [23]. The fatigue crack occurs at the specimen surface in the short life region at a relatively Typical examples of fracture surfaces in the respective fracture modes are shown in Figure 2, where (a) gives the SEM observation of the fracture surface in the surface-induced fracture mode and (b) is the fracture surface in the interior-induced fracture mode [23].…”

“…Typical examples of fracture surfaces in the respective fracture modes are shown in Figure 2, where (a) gives the SEM observation of the fracture surface in the surface-induced fracture mode and (b) is the fracture surface in the interior-induced fracture mode [23]. The fatigue crack occurs at the specimen surface in the short life region at a relatively Typical examples of fracture surfaces in the respective fracture modes are shown in Figure 2, where (a) gives the SEM observation of the fracture surface in the surface-induced fracture mode and (b) is the fracture surface in the interior-induced fracture mode [23]. The fatigue crack occurs at the specimen surface in the short life region at a relatively high stress level, as shown in Figure 2a.…”