PSI - Issue 75

D. Jbily et al. / Procedia Structural Integrity 75 (2025) 158–175 Author name / Structural Integrity Procedia (2025)

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Fig. 16. E-77 tribometer schematic

Fig. 17. Image of specimens used in tribological characterization tests.

The initial contact pressure is 1400 MPa, the average speed is 0.2 m/s, and the temperature is 80°C in Mobilgear 600 XP150 oil, identical to those used in the gear test. The tests were conducted with three different durations: • The first test lasted 1,000 seconds (20,000 cycles), corresponding to the duration specified in the ASTM G 133 standard. • The second test comprised 270,000 cycles, equivalent to the running-in phase (2 hours at 2250 rpm) of the back-to-back test. • The third test involved 340,000 cycles, which corresponds to the point at which the first signs of micropitting were observed on the gear teeth during the back-to-back test. If the material and the heat treatment of the lower cylinder are representative of the tooth, a significant difference in roughness is noted for this cylinder machined by hard turning. The R a of the REF pinion cylinder is 0.86 µm and that of the SP is 0.74 µm, while the R a of the REF tooth is 0.34 µm and that of the SP is 0.41 µm.

Table 1 presents a summary of the test conditions for the six experiments conducted using a reciprocating contact setup. The tests involved reference (REF) and shot peened (SP) samples under identical conditions.

Table 1. Test Conditions.

Test

Cylinder 1

Cylinder 2

Acquisition

Stroke

Frequency

Load

Test Duration

Number

Max Stress