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Some aspects of friction measurements in hip joint simulators

Unsworth, A.

Authors

A. Unsworth



Abstract

The measurement of friction in artificial hip joints can lead to the knowledge of the lubrication mechanisms occurring in the joints. However, the measurement of friction, particularly in spherical contacts, is not always straightforward. The important loading and kinematic features must be appropriate and the friction must be measured in the correct plane. Even defining a coefficient of friction is difficult with spherical contacts as friction acts at different moment arms throughout the contact area. Thus, the generated frictional torques depend on the pressure distribution of the contact and the moment arms at which this pressure acts. The pressure distribution depends on the material properties, the surface entraining velocities, the joint diameters, and the clearance between the two surfaces of the ball and socket joint. Equally measuring friction is very taxing for machines which are applying very high loads. Slight misalignments of the application of these loads can produce torques which are very much greater than the frictional torques that we are trying to measure. This article attempts to share the thoughts behind over 40 years of measuring friction in artificial joints using the Durham Friction Simulators. This has led to accrued consistency of measurement and a robust scientific design rationale to understand the nature of friction in these spherical contacts. It also impacts on how to obtain accurate measurements as well as on the understanding of where the difficult issues lie and how to overcome them.

Citation

Unsworth, A. (2016). Some aspects of friction measurements in hip joint simulators. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 230(5), 359-365. https://doi.org/10.1177/0954411916637382

Journal Article Type Article
Acceptance Date Feb 9, 2016
Online Publication Date May 9, 2016
Publication Date 2016-05
Deposit Date Jun 13, 2016
Journal Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine
Print ISSN 0954-4119
Electronic ISSN 2041-3033
Publisher SAGE Publications
Peer Reviewed Peer Reviewed
Volume 230
Issue 5
Pages 359-365
DOI https://doi.org/10.1177/0954411916637382
Public URL https://durham-repository.worktribe.com/output/1409684