Compliant Foil Bearings Technology and their Application to High Speed Turbomachinery

Heshmat, H. and Hermel, P. “Compliant Foil Bearings Technology and their Application to High Speed Turbomachinery,” 19th Leeds-Lyon Symposium on Thin Film in Tribology – From Micro Meters to Nano Meters, Leeds, U.K., September 1992, D. Dowson, C. M. Taylor, T. H. C. Childs, M. Godet and G. Dalmaz  (Editors), (1993) Elsevier Science Publishers B.V., pp. 559-575.

This paper describes the second part of an investigation into the mechanism of deformation of the corrugated foil (bump foil) strips used in compliant surface foil bearings.  In the earlier work, a theoretical model was developed to predict the structural characteristics of bump foil strips under various loads, including the effects of the friction forces between the compliant elements, local interaction forces, load distribution profiles, and bump configurations.  In the experiments described herein, two-dimensional deflections of bump foils were recorded via an optical tracking system for a wide range of operating conditions to verify the feasibility of the theoretical model.  Test results corroborate the theoretical model for the linear regions of load and the deflection parameters.  The effects of the bearing design parameter, such as bump configuration, load profile, and surface coating and lubricant, on the structural characteristics of the bump foil strip were investigated.  in addition, the source and mechanism of nonlinear behavior of the bump foil strips under light load conditions were examined, and more effective methods of achieving both Coulomb damping and optimum structural compliance were investigated.  An understanding of the analytical and semi-empirical relations resulting from this work offers designers the potential for enhancing the design of high-performance compliant foil bearings. 

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