Frictional aging, de-aging, and re-aging in a monolayer-coated micromachined interface

Abstract

Measurements on monolayer-coated polycrystalline silicon surfaces have shown that the static friction coefficient s strongly depends on loading parameters including hold time and normal hold force by Corwin and de Boer ͓J. Microelectromech. Syst. 18, 250 ͑2009͔͒. In that work, s was measured by keeping the tangential force constant and lowering normal force until motion occurred. Results indicated that s also depends strongly on normal force ramp-down rate. Here, we postulate that if the normal load is lowered instantaneously, the time for the block to begin moving, the "release time" t r , will be greater than the inertial response time, which is on the order of 5 s. We measure the release time and find that it spans nearly six decades from less than 100 s to almost 50 s. Release time depends on the loading and unloading history through all three of the parameters varied: hold time, hold force, and release force. An empirical model incorporating all three of these parameters fits the release time data over the full range. Release time decreases after the contacting surfaces are held together at increasing hold force levels and this qualitatively explains a previous observation that static friction aging is suppressed with increasing normal force at a fixed tangential load in this interfacial system. We further quantitatively relate the previous s loading dependence on all three parameters to the release time model established here by introducing a "re-aging" parameter. This work firmly establishes that release time is a more fundamental parameter than the static friction coefficient and is the origin of static friction coefficient dependencies in this micromachined interface.

Stick–Slip Instabilities for Interfacial Chemical Bond-Induced Friction at the Nanoscale

“…Friction is important in a wide range of technological, industrial, biological, and natural systems. − One general approach to describe macroscale frictional behavior is based on rate and state friction (RSF) laws, − which, despite their designation as “laws”, are largely empirical in form, lacking a robust physical basis. Nevertheless, RSF laws fit reasonably well the data in friction experiments, including trends of friction as a function of time and sliding rate, for a remarkably wide range of materials, including organic monolayer-coated microelectromechanical systems, ,, paper, granular media, and rocks. ,,,− …”

Multiphysics model of chemical aging in frictional contacts

“…Solid-solid frictional interfaces can undergo significant evolution over the time they are held in a stationary contact prior to sliding. This so-called frictional aging [1-5] is known to play a critical role in nucleation and recurrence of earthquakes [5], and also has a large influence on the performance and durability of microelectromechanical systems [6][7][8]. In general, aging has been attributed either to a change in contact area due to plastic deformation and/or to the change in quality of the interface due to chemical strengthening of the interface.…”

Load and Time Dependence of Interfacial Chemical Bond-Induced Friction at the Nanoscale

“…empirical and lack a robust physical basis. In spite of this, RSF laws fit friction data for a remarkably wide range of materials including paper [11], organic monolayer-coated microelectromechanical systems [1][2][3], and granular media and rocks [4,6,8,[11][12][13][14].…”