PSI - Issue 57

Guillaume THOQUENNE et al. / Procedia Structural Integrity 57 (2024) 191–198

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Author name / Structural Integrity Procedia 00 (2019) 000 – 000

Table 1: Ratio  D / UTS, for 10 million cycles and 50% of probability of failure [3].

Type of solicitation

 D / UTS ratio

Torsion

0.35

Table 2: Mechanical properties of the 42CrMo4 induction hardened steel.

YS (MPa) 1 817

Hardness (HV)

UTS (MPa) 2 138 1 091

 D (*) (MPa)

Position Surface

660 330

748 382

Core

927

(*)  D is given for 10 million cycles and 50% probability of failure.

4.3. Crack initiation design The objective of the fatigue sizing of the specimen is to ensure that the fatigue cracks initiation will be at the transition zone and not at the Hertz depth. We thus led a parametric numerical simulation by considering different specimen radius of curvature (from 17.5 mm to 300 mm) and different IHD. By comparing the shear fatigue limit and the hertzian shear stress profiles, we found the combination [IHD; radius of curvature] which maximizes the risk of cracks initiation in the transition zone and minimizes it at the Hertz depth (Fig. 4).

Fig. 4. Fatigue sizing of the twin-disc machine specimens.

4.4. Plastic strain design To prevent plastic strain due to the static load applied, we dimension the specimen geometry and the heat treatment characteristics to obtain Von Mises stresses, computed by finite element method, below the yield strength of the material (see Fig. 5).