Friction RandomPOD—A new method for friction measurement in noncyclic, multidirectional, dynamic pin-on-disk tests for orthopaedic bearing materials

Vesa Saikko*, Omar Morad, Raine Viitala

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

Abstract

The 16-station, computer-controlled RandomPOD wear test device was re-designed into a friction measurement device, Friction RandomPOD. The motion was implemented by a servo-electric x-y-stage and the load was proportional-pneumatic. The direction of sliding, velocity (v), acceleration, and the magnitude of the load (L) varied randomly and continuously. The nominal contact pressure p varied between 0 and 2.4 MPa and v between 0 and 40 mm/s. In the first version of the device, the frictional force components were continuously measured by two miniature load cells in two perpendicular directions. In the second version, the measurement was done with a three-axial, commercial load cell. The resultant frictional force was divided by the instantaneous load in order to obtain the coefficient of friction (μ) at a frequency of 200 Hz. Due to the light and accurate design of the device, vibrations were absent in the measured signals although the measurements were most dynamic. Hence no filtering was needed. Serum lubricated polyethylene/CoCr tests revealed non-symmetric distributions of μ, friction power Pμ, and μ vs. pv.

Original languageEnglish
Article number110273
Number of pages7
JournalJournal of Biomechanics
Volume118
Early online date29 Jan 2021
DOIs
Publication statusPublished - 30 Mar 2021
MoE publication typeA1 Journal article-refereed

Keywords

  • Dynamic friction measurement
  • Extensively cross-linked UHMWPE
  • Noncyclic pin-on-disk
  • Orthopaedic tribology
  • Servo-drive

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