PSI - Issue 19

Vincent ARGOUD et al. / Procedia Structural Integrity 19 (2019) 719–728

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V. ARGOUD et al. / Structural Integrity Procedia 00 (2019) 000–000

(b) Notched specimen fracture surface.

(a) Gear tooth fracture surface.

(d) Gear tooth crack initiation site (10 7 cycles at 1350 MPa + 4 018 836 cycles at 1500 MPa)

(c) Gear tooth crack initiation site (36 465 cycles at 1400 MPa).

(e) Notched specimen crack initiation site (16 881 cy cles at 1600 MPa).

(f) Notched specimen crack initiation site (22 163 cy cles at 1600 MPa).

Fig. 14: Fatigue failure surfaces of gear specimens and notched specimens.

SAE 4320 steel (Cohen et al. , 1991) and SAE 8620 steel (Spice et al. , 2002), on four points bending tests on smooth semi-cylindrical specimens made of carburized AISI 8620 steel (Apple et al. , 1973) or on axial tension-compression fatigue tests on notched cylindrical specimens made of gaz-nitrided AISI 4140 steel (Limodin et al. , 2006). However, in some other studies, this phenomenon is not observed. For instance, the Wo¨hler diagrams of the fatigue tests of Asi et al. (2009) (rotating bending on smooth cylindrical specimen, carburized SAE 8620 steel) and of Zhang et al. (2013) (STBF tests on carburized 20CrMoH gears) do not show any particular scatter. For now, among the di ff erent parameters (steel composition, thermochemical treatment, specimen geometry, sort of tests . . . ), the authors are unable