Surface Hierarchy: Macroscopic and Microscopic Design Elements for Improved Sliding on Ice

Karlis Agris Gross,Ilze Jerane,Michael J Wood,Anne-Marie Kietzig,Ernests Jansons,Janis Lungevics

doi:10.3390/lubricants9100103

Karlis Agris Gross, Ilze Jerane + Show 4 more

Open Access

https://doi.org/10.3390/lubricants9100103

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Abstract

Frictional interaction with a surface will depend on the features and topography within the contact zone. Describing this interaction is particularly complex when considering ice friction, which needs to look at both the macroscopic and microscopic levels. Since Leonardo da Vinci shared his findings that roughness increases friction, emphasis has been placed on measuring surface coarseness, neglecting the contact area. Here, a profilometer was used to measure the contact area at different slicing depths and identify contact points. Metal blocks were polished to a curved surface to reduce the contact area; further reduced by milling 400 µm grooves or laser-micromachining grooves with widths of 50 µm, 100 µm, and 150 µm. Sliding speed was measured on an inclined ice track. Asperities from pileup reduced sliding speed, but a smaller contact area from grooves and a curved sliding surface increased sliding speed. An analysis of sliding speed versus contact area from incremental slicing depths showed that a larger asperity contact surface pointed to faster sliding, but an increase in the polished surface area reduced sliding. As such, analysis of the surface at different length scales has revealed different design elements—asperities, grooves, curved zones—to alter the sliding speed on ice.

Highlights

Published: 12 October 2021Ice friction draws on the initial finding by Leonardo di Vinci, that friction between two surfaces varies linearly with the force applied to a surface, acting through the contact area.Recent explanations of ice friction have been interpreted through lower friction from a lubricant film [1] or by considering the thermodynamics at the sliding interface [2]
Aspects contact area and asperities will first be addressed on a block with wider Aspects of contact asperities will first be addressed on a block with grooves, followed by a area new and
The analysis showed the dominating role of asperities and so further work could consider how asperity nanotopography interacts with ice to influence the sliding speed

Summary

Introduction

Published: 12 October 2021Ice friction draws on the initial finding by Leonardo di Vinci, that friction between two surfaces varies linearly with the force applied to a surface, acting through the contact area.Recent explanations of ice friction have been interpreted through lower friction from a lubricant film [1] or by considering the thermodynamics at the sliding interface [2]. Ice friction draws on the initial finding by Leonardo di Vinci, that friction between two surfaces varies linearly with the force applied to a surface, acting through the contact area. The goal of this work was to evaluate the contact area at the macro-scale and the micro-scale to see the effect of sliding over ice and propose further characterization at the nanoscale. Few ice-friction studies have investigated the effect of the contact area. Initial experiments from 1939—in a cave dug out from ice at Jungfraujoch in the Swiss Alps—showed a slight increase in the friction coefficient with contact area, where the contact area varied from 2 to 300 mm2 [3]. Experiments on a larger tribometer with a more pliable polyethylene slider (contact area: 200–1000 mm2 ) on ice displayed a larger change in friction [4]

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