Cobblestone model

Israelachivil et al. [25] proposed a phenomenal model for describing the interrelations between friction and adhesion. Consider the system shown in Fig. 28, where a spherical molecule slides over a corrugated solid surface. The scenario is somehow like pushing the wheel of a cart over a road paved with cobblestones, so it is also known as the cobblestone model. 

Fig. 28—The cobblestone model of friction, a spherical molecule moving on atomic roughness (reproduced after Ref. [24]).

Figure 20.5. Schematic of the cobblestone model . Work must be done to separate the two surfaces to permit sliding. The surfaces then crash back into the next stable position, and some of this energy is lost as heat and sound...

In recent years it has been demonstrated that also adhesion (or adhesion hysteresis) plays an important role in friction. Israelachvili and coworkers could show that friction and adhesion hystereses are, in general, directly correlated if certain assumptions are fulfilled. These authors have proposed models based on data obtained by surface forces apparatus (SFA) experiments, e. g. the cobblestone model of interfacial friction (4). In addition, several groups described the application of continuum contact mechanics (e.g. Johnson-Kendall-Roberts (JKR) theory (5)) to describe friction data measured between flat surfaces and nanometer sized contacts (d). 

Discussion with Respect to the Cobblestone Model of Interfacial Friction (4). Let... 

The HCE-T model was established in 1995 by Araki-Sasaki and coworkers [56], It was formed by transfection of human corneal epithelial cells from a 47-year-old female donor with a recombinant SV40-adenovirus, which lacked the origin of viral replication (i.e., not able to produce viral particles). The cell line has good growth characteristics and shows a cobblestone-like appearance. The cell line is intensively used by Urtti and coworkers and represents a standard... 

The Objective Scientists Model as published in the 1995 organizational brochure of The American College of Forensic Examiners, 1658 South Cobblestone Court, Springfield, MO. (Note This is similar to oaths and principles espoused by numerous scientific societies that oblige its members to be objective when evaluating and interpreting scientific data.)... 

Anisotropic friction and molecular stick-slip friction were observed on a number of polymer systems by LFM using non-functionalized and functionalized tips. The observations described in this paper can be understood within the frame of the cobblestone (interlocking asperity) model. For a quantitative description, however, important parameters such as the energy fraction dissipated during the kinetic friction process (e) are still lacking. 

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