PSI - Issue 57

Guillaume THOQUENNE et al. / Procedia Structural Integrity 57 (2024) 191–198 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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5.2.2. Residual stresses analysis In this study, we do not consider the residual stresses which are not generally known in industrial components and are considered constant in time of manufacturing. However, to be conscious of the levels of those residual stresses and to verify the homogeneity of specimen manufacturing process, profile X-Ray diffraction measurements have been made before and after the fatigue tests. As shown in Fig. 9, after the heat treatment, the hardened zone, up to about 800 µm, is in compression while the untreated material, deeper than 800 µm is in tension. After the tests, due to the low applied stresses, the residual stresses profile did not change a lot, we only see an increase of the stresses, as the compressive zone as the tensive zone, by about 200 MPa.

Fig. 9. Residual stresses profiles before and after rolling contact fatigue tests.

6. Conclusion and future work This first part of the project allowed us to design the geometry of twin-disc machine specimens and the induction hardening heat treatment characteristics in order to reproduce the failure mode of large dimension pieces (bearings or gears for example). The main difficulty in this sizing is the confrontation of the two main considerations: plasticity and fatigue. They lead to a tight interval of geometrical and mechanical design. As we do not have enough test results to perform an accurate analysis, additional tests are in progress, in the same conditions, with the objective of reproduce the failure mode. As the fatigue and static specimen sizing common range is very tight, slightly different condition tests have to be conducted, with a different IHD, in order to obtain more robust results and to set up easy to use design rules.

7. References [1] Increase in Contact Strength of Heavy-Loaded Rolling Bearings for Gear Drives and Transmissions E.Tesker Mechanisms and Machine Science 51 (2018), pp 205-220

[2] ISO 18265:2013 – Metallic materials — Conversion of hardness values [3] Cetim material fatigue datasheet for 42CrMo4 steel “B03 - 42CrMo4”