A Homodyne Quadrature Laser Interferometer for Micro-Asperity Deformation Analysis

A. Pogačnik, T. Požar, M. Kalin, J. Možina

Sensors 13 (2013) 703-720.


We  report  on  the  successful  realization  of  a  contactless,  non-perturbing,  displacement-measuring  system for  characterizing  the  surface  roughness  of  polymer materials used in tribological applications. A single, time-dependent, scalar value, dubbed the  collective  micro-asperity  deformation,  is  extracted  from  the  normal-displacement measurements of normally loaded polymer samples. The displacement measurements with a sub-nanometer resolution are obtained with a homodyne quadrature laser interferometer.
The  measured  collective  micro-asperity  deformation  is  critical  for  a  determination  of  the real  contact  area  and  thus  for  the  realistic  contact  conditions  in  tribological  applications. The designed measuring system senses both the bulk creep as well as the micro-asperity creep occurring at the roughness peaks. The final results of our experimental measurements are three time-dependent values of the collective micro-asperity deformation for the three selected  surface  roughnesses.  These  values  can  be  directly  compared  to  theoretical deformation curves, which can be derived using existing real-contact-area models.

Keywords: Micro-asperity, Deformation, Real contact area, Roughness, Polymer, Creep, Tribology, Laser interferometry, Homodyne detection, Displacement

URL: http://www.mdpi.com/1424-8220/13/1/703

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