Role of asperity creep in time- and velocity-dependent friction of a polymer glass
Laboratoire de Physique de la Matière Condensée, École Normale
Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France
Accepted: 29 January 1998
We study time-strengthening and velocity-weakening friction of poly(methyl methacrylate) from room temperature up to the glass transition. The role of creep of asperities under normal load is systematically investigated. It is confirmed to be a primary cause of ageing of the static friction force. Velocity weakening is also strongly enhanced on approaching the glass transition, whence promoting stick-slip oscillations. The quantitative analysis of sliding friction, based on a widely used rule of "time and velocity equivalence”, is found to be inadequate in the transition region.
PACS: 46.30.Pa – Friction, wear, adherence, hardness, mechanical contacts, and tribology / 62.20.Hg – Creep / 68.35.Gy – Mechanical and acoustical properties; adhesion
© EDP Sciences, 1998