Experimental evidence of non-Amontons behaviour at a multicontact interface

TL;DR

This study measures normal stress fields at a multicontact interface, revealing deviations from Amontons' law due to interface compliance, with results varying under dry and lubricated conditions.

Contribution

It provides experimental evidence of non-Amontons behavior at multicontact interfaces using innovative MEMS sensors and compares results with finite element predictions.

Findings

Deviations from Amontons' law decrease with load

Lubrication restores predicted stress profiles

Finite compliance explains observed deviations

Abstract

We report on normal stress field measurements at the multicontact interface between a rough elastomeric film and a smooth glass sphere under normal load, using an original MEMS-based stress sensing device. These measurements are compared to Finite Elements Method calculations with boundary conditions obeying locally Amontons' rigid-plastic-like friction law with a uniform friction coefficient. In dry contact conditions, significant deviations are observed which decrease with increasing load. In lubricated conditions, the measured profile recovers almost perfectly the predicted profile. These results are interpreted as a consequence of the finite compliance of the multicontact interface, a mechanism which is not taken into account in Amontons' law.