PSI - Issue 24

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Vincenzo D’Addio et al. / Procedia Structural Integrity 24 (2019) 510–525 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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lubricant). Once the corresponding contacts are created, the correct parameters have to be defined; in particular the stiffness parameter is the most important one and a static simulation campaign was carried out to tune the model. The single static simulation consists in applying two load steps (Fig. 12): in the first one the axial preload is introduced and in the second one a radial load from 0 to 40 N is gradually applied (‘quasi - static’ force) in order to obtain the relationship between radial force and radial displacement and consequently the global radial stiffness of the virtual bearing Kr which has to be compared with the real radial stiffness taken from the corresponding datasheet (for the set preload and internal clearance).

Fig. 12. First load step: axial preload (left); second load step: radial load (from 0 to 40 N) (right). Starting from an initial value of the stiffness contact parameter k 0 (estimated with the contact Hertz theory), by an iterative procedure, a global stiffnes Kr = 1.4 ∙ 10 6 N/mm was obtained, quite close to the real one. For the other parameters the values recommended by the software for metal to metal contacts were used. A localized defect on the outer ring was taken into account. In particular, a semi-spherical cut with a radius of 10  m (same order of magnitude of the Hertzian contact imprint) was located on the respective race, so that the rolling elements hit it during their motion (Fig. 13).

Fig. 13. Localized defect on outer ring.

To be able to perform the simulations, the integration method was changed from GSSTIFF to HASTIFF, that is a robust variant of Newmark method more indicated for these applications. Moreover another parameter known as “ Contact Faceting Toleran ce” was modified from default 300 to 1.65 ∙ 10 5 (3 orders higher) thus significantly improving the accuracy in meshing the contact surfaces.