Changes in the cross-country ski base properties resulting from the ski use
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ORIGINAL ARTICLE
Changes in the cross-country ski base properties resulting from the ski use Esa Puukilainen • Olli Ohtonen • Teemu Lemmettyla¨ • Vesa Linnamo Bjo¨rn Hemming • Toni Laurila • Salla Tapio • Markku Ra¨sa¨nen • Mikko Ritala • Markku Leskela¨
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Published online: 6 September 2013 Ó International Sports Engineering Association 2013
Abstract In this work, changes in the cross-country ski base properties resulting from stone grinding, skiing, waxing and re-stone grinding have been investigated. The surface topography, crystallinity, wettability and sliding properties of cross-country ski bases were recorded using a selection of measurement techniques: non-contact chromatic confocal microscopy, contact-type surface roughness analyser and scanning electron microscopy (topography), Raman spectroscopy (crystallinity), contact angle measurement (wettability) and a ski tester (sliding properties). The tested skis were used for 150 km and waxed 35 times. The ski base surface became smoother and the orientation and crystallisation of the base material increased. Wear decreased the hydrophobicity and increased the sliding friction. Even though re-grinding did not restore all of the
E. Puukilainen M. Ritala M. Leskela¨ (&) Laboratory of Inorganic Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, 00014 Helsinki, Finland e-mail: [email protected] O. Ohtonen T. Lemmettyla¨ V. Linnamo Department of Biology of Physical Activity, Sports Technology Unit, University of Jyva¨skyla¨, Kidekuja 2, 88610 Vuokatti, Sotkamo, Finland B. Hemming T. Laurila Centre for Metrology and Accreditation (MIKES), P.O. Box 9, 02151 Espoo, Finland T. Laurila Department of Signal Processing and Acoustics, Metrology Research Institute, Aalto University, P.O. Box 13000, 02150 Espoo, Finland S. Tapio M. Ra¨sa¨nen Laboratory of Physical Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, 00014 Helsinki, Finland
ski base properties, re-grinding improved the wettability and sliding properties. The results help to optimise stone grinding interval to maintain the performance of the skis. Keywords Ski base Topography Crystallinity Wettability Sliding friction
1 Introduction A ski sliding on snow or ice involves a number of physical and chemical interactions. Several parameters of both the snow and the ski affect the observed sliding friction. The friction of snow and ice has been studied in the past few decades [1–9]. Bowden and Hughes [1] found that the low friction coefficient on snow or ice is primarily caused by the melt-water lubrication though frictional heating. Since then, several research groups have approached snow and ice friction from different points of view and confirmed the first findings [2–5]. The base material of a ski is one of the major factors determining the sliding friction. Ultra high molecular weight polyethylene (UHMWPE) is currently the most common material for the ski running surface. UHMWPE is a semi-crystalline polymer having long polymer chains, wi
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