Elastohydrodynamics for Soft Solids with Surface Roughness: Transient Effects
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A huge number of technological and biological systems involve the lubricated contact between rough surfaces of soft solids in relative accelerated motion. Examples include dynamical rubber seals and the human joints. In this study, we consider an elastic cylinder with random surface roughness in accelerated sliding motion on a rigid, perfectly flat (no roughness) substrate in a fluid. We calculate the surface deformations, interface separation and the contributions to the friction force and the normal force from the area of real contact and from the fluid. The driving velocity profile as a function of time is assumed to be either a sine function, or a linear multi-ramp function. We show how the squeeze-in and squeeze-out processes, occurring in accelerated sliding, quantitatively affect the Stribeck curve with respect to the steady sliding. Finally, the theory results are compared to experimental data.
KeywordsRubber friction Wet contact Soft contact Lubrication Transient contact Seals Tires
We thank S.-C. Vladescu and T. Reddyhoff (Ref. ) for supplying the numerical data used for Fig. 13 and 14. This work was performed within a Reinhart-Koselleck project funded by the Deutsche Forschungsgemeinschaft (DFG). We would like to thank DFG for the project support under the reference German Research Foundation DFG-Grant: MU 1225/36-1. The research work was also supported by the DFG-Grant: PE 807/10-1 and DFG-Grant No. HE 4466/34-1. MS acknowledges FZJ for the support and the kind hospitality received during his visit to the PGI-1. Finally, MS also acknowledges COST Action MP1303 for grant STSM-MP1303-171016-080763.
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