Title

SHANNON ENTROPY AS A CHARACTERISTIC OF A ROUGH SURFACE: WHY THE RUNNING-IN TRANSIENT PROCESS LEADS TO FRICTION REDUCTION

SHANNON ENTROPY AS A CHARACTERISTIC OF A ROUGH SURFACE: WHY THE RUNNING-IN TRANSIENT PROCESS LEADS TO FRICTION REDUCTION

Authorship

Nosonovsky, Michael; Mortazavi, Vahid

Nosonovsky, Michael

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Mortazavi, Vahid

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DOI

10.5151/5463-5463-17171

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Abstract

When friction is initiated, there is a certain transient period, referred to as the “running- in”, during which friction and wear decrease to their stationary value. During the running-in period, the surfaces roughness of contacting solid surfaces changes, until it reaches a certain equilibrium value and thus the adjustment of surfaces to each other occurs. This process can be viewed as self-organization that leads to minimized energy dissipation and thus minimum friction and wear]. In this research, theoretically and experimentally, the minimization of friction and wear by adjustment of surface roughness to an equilibrium value during the running-in transient process was investigated. A control model, using feedback loop due to the coupling of two mechanisms, was developed with Matlab / Simulink software. The time-dependence of the coefficient of friction and roughness parameter during the simulated running-in process were analyzed. In order to check whether the self-organization occurs, the Shannon entropy of a rough profile was calculated. The Shannon entropy is a generalization of the thermodynamic entropy for the information theory. A surface profile with lower Shannon entropy is “more ordered” (or “less random”) than a profile with a higher Shannon entropy, and, therefore, decreasing Shannon entropy during the transient process is an indication of self-organization.

When friction is initiated, there is a certain transient period, referred to as the “running- in”, during which friction and wear decrease to their stationary value. During the running-in period, the surfaces roughness of contacting solid surfaces changes, until it reaches a certain equilibrium value and thus the adjustment of surfaces to each other occurs. This process can be viewed as self-organization that leads to minimized energy dissipation and thus minimum friction and wear]. In this research, theoretically and experimentally, the minimization of friction and wear by adjustment of surface roughness to an equilibrium value during the running-in transient process was investigated. A control model, using feedback loop due to the coupling of two mechanisms, was developed with Matlab / Simulink software. The time-dependence of the coefficient of friction and roughness parameter during the simulated running-in process were analyzed. In order to check whether the self-organization occurs, the Shannon entropy of a rough profile was calculated. The Shannon entropy is a generalization of the thermodynamic entropy for the information theory. A surface profile with lower Shannon entropy is “more ordered” (or “less random”) than a profile with a higher Shannon entropy, and, therefore, decreasing Shannon entropy during the transient process is an indication of self-organization.

Keywords

Friction; Entropy.

Friction; Entropy.