Detachment fronts and the onset of dynamic friction

Abstract

The dynamics of friction have been studied for hundreds of years, yet many aspects of these everyday processes are not understood. One such aspect is the onset of frictional motion (slip). First described more than 200 years ago as the transition from static to dynamic friction, the onset of slip is central to fields as diverse as physics, tribology, mechanics of earthquakes and fracture. Here we show that the onset of frictional slip is governed by three different types of coherent crack-like fronts: these are observed by real-time visualization of the net contact area that forms the interface separating two blocks of like material. Two of these fronts, which propagate at subsonic and intersonic velocities, have been the subject of intensive recent interest. We show that a third type of front, which propagates an order of magnitude more slowly, is the dominant mechanism for the rupture of the interface. No overall motion (sliding) of the blocks occurs until either of the slower two fronts traverses the entire interface.

Gutenberg-Richter's law in sliding friction of gels

“…Other than the spike-like patterns indicating the large and rapid propagation of detachment fronts (corresponding to large force drops in Figure 2g), small, intermittent and step-like events of the detached regions (corresponding to small force drops) were clearly observed prior to large slip events. These behaviors are similar to those observed for the frictional system between two PMMA blocks by Rubinstein et al [2004Rubinstein et al [ , 2006Rubinstein et al [ , 2007Rubinstein et al [ , 2008: the onset of large frictional motion is preceded by a discrete sequence of precursor events.…”

Recent developments in dynamic fracture: some perspectives

“…As shown in Fig. 9, these new experiments have revealed various rupture modes that are loosely classified as follows: slow ruptures, which propagate far below the material wave speeds [141,[146][147][148], "sub-Rayleigh" ruptures [141,146,147,149] that propagate up to the Rayleigh wave-speed c R , and "super-shear" rupture modes that surpass the shear wave-speed c s [141,146,[149][150][151][152]. It is important to note that analogs of all of these rupture modes have been documented in natural earthquakes [144,145,[153][154][155][156].…”

“…Super-shear cracks have long been considered in the fracture literature [3,199,200], but until they were observed in the beautiful experiments by Rosakis and coworkers [151], they were often considered to be of purely theoretical value. Since this first observation in weakly bonded homogeneous blocks that were ballistically loaded, mode II super-shear ruptures have been observed numerically [201][202][203] as well as in a variety of other scenarios that include frictional interfaces and quasi-static loading [141,146,149,152].…”

“…What is the origin and nature of the experimentally observed "slow fronts" [141,146]? Recent theoretical work has suggested that they may be a direct result of the qualitative form of the friction law at the interface; the frictional constitutive law can also affect the existence and nature of propagating rupture fronts.…”

Current trends in the physics of nanoscale friction

“…The proposed mean-field model provides a microscopic basis for the macroscopic description in terms of rate-and-state equations. In several works by J. Fineberg's group [2][3][4] the transition from sticking to sliding is characterized by slip fronts propagating along the interface. Several works have modeled this transition using various techniques including a master-equation type of approach [5][6][7][8][9][10], mesoscopic models [11], and finite-elements techniques [12][13][14].…”