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A Micro-Machine to Study the Fatigue of Rough Contacts


The surface roughness evolution in lubricated contacts is a crucial step in the fatigue prediction process. The latter is initially conditioned by the running in process and finally by surface fatigue. This work aims at understanding and predicting rolling contact fatigue with a particular emphasis on the very first cycles. It is based on a combined experimental and numerical approach. The current paper is centred on the experimental description. A major difficulty in understanding surface degradation is the measurement of the surface roughness evolution at the relevant scales. In fact, current twin disc machines allow a global study of the contact behaviour (normal and tangential load) but it is necessary to dismount the system for each roughness measurement. Furthermore, the duration and costs are important as each pair of discs provides only a single surface observation (at the end of the test). A twin disc micro-machine, called μMag, developed at the LaMCoS laboratory, was specially designed for this kind of surface roughness analysis. The μMag allows the observation in situ of the disc surface during the test interruption. This avoids dismounting discs, a major cause of perturbations and inaccuracies. This test system offers an accurate and continuous control of the kinematics and load parameters. At each test interruption, the surface topography is measured using an optical profiler. Marks on the surface allow very accurate relocalisation of the same profile. This is essential to follow the running in mechanism and for efficient numerical simulations. Contact stress calculations are performed using analytical [1] and numerical [2] tools. The crowned disc is turned, with a roughness of 0.6 μm. The cylindrical disc is honed, its roughness is less than 0.01 μm, therefore the cylindrical disc is called the smooth disc. The first results obtained with the μMaG apparatus are presented in this paper. The surface geometry is observed at the end of the first, fifth and tenth cycle.The steady state of the surface deformation is obtained after few cycles and marks to the end of the running in period. An FFT based simulation of the experiments is carried out using the actual initial surface topography of both discs. The elastoplastic model developed by Mayeur et al. [3] was used with a bi linear constitutive law. The experimental surface topography at the end of the running in period is compared with the numerical results. This procedure is repeated up to 1 Million cycles leading to surface crack initiation.
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hal-01004368 , version 1 (11-06-2014)


  • HAL Id : hal-01004368 , version 1


Laure Berthe, Philippe Sainsot, Antonius Lubrecht, Marie-Christine Baietto. A Micro-Machine to Study the Fatigue of Rough Contacts. ASME/STLE 2012 International Joint Tribology Conference, Oct 2012, Denver, Colorado, United States. ⟨hal-01004368⟩
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