Date of Award

December 2013

Degree Type

Thesis

Degree Name

Master of Science

Department

Engineering

First Advisor

Kurt E. Beschorner

Committee Members

Pradeep L. Menezes, Michael Nosonovsky

Abstract

Slips and falls are one of the leading causes of occupational accidents. Understanding the important factors that affect shoe-floor friction is vital for identifying unsafe surfaces and designing better footwear and flooring. While the shoe-floor coefficient of friction is known to be dependent on several factors including shoe and floor roughness, shoe speed, shoe material, and normal load, the mechanisms that cause these effects are not very well understood. The objective of this thesis is to develop a finite element model that simulates the microscopic asperity interaction between shoe and floor surfaces and apply it to quantify the effect of shoe material, topography, loading and sliding speed on shoe-floor adhesion and hysteresis friction.

Recent studies have concluded that boundary lubrication is highly pertinent to slipping and that adhesion and hysteresis are the main friction components in boundary lubrication. To have a better knowledge about the mechanisms governing the boundary lubrication friction at the microscopic asperity interaction level, a three dimensional computational model of two rough surfaces is developed which calculates the friction force due to hysteresis and real area of contact (which is proportional to adhesion friction). The computer model includes two rough surfaces of rubber and rigid material. A viscoelastic material model based on parameters calculated from experiments is used to simulate the shoe material. In addition, surface to surface contact algorithm is used for simulating the interaction of the two rough surfaces. The results show that microscopic shoe and floor roughness, followed by material properties, shoe sliding speed, and normal loading affect hysteresis and adhesion coefficient of friction. The model provides an improved insight about the mechanisms that cause changes in adhesion and hysteresis when altering shoe and floor roughness, sliding speed, shoe material and normal loading and it can be useful in development of slip resistant shoes and floorings.

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