Determination of coefficients of friction for laminated veneer lumber on steel under high pressure loads
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ISSN 2223-7690 CN 10-1237/TH
RESEARCH ARTICLE
Determination of coefficients of friction for laminated veneer lumber on steel under high pressure loads Michael DORN1,*, Karolína HABROVÁ2, Radek KOUBEK3, Erik SERRANO4 1
Department of Building Technology, Linnaeus University, Växjö 35252, Sweden
2
Czech University of Life Sciences Prague-Department of Materials and Engineering Technology, Prague 16521, Czech Republic
3
Daikin UK, The Heights, Brooklands, Weybridge, KT13 0NY, United Kingdom
4
Division of Structural Mechanics, Lund University, Lund 22100, Sweden
Received: 22 November 2018 / Revised: 28 September 2019 / Accepted: 24 February 2020
© The author(s) 2020. Abstract: In this study, static coefficients of friction for laminated veneer lumber on steel surfaces were determined experimentally. The focus was on the frictional behaviors at different pressure levels, which were studied in combination with other influencing parameters: fiber orientation, moisture content, and surface roughness. Coefficients of friction were obtained as 0.10–0.30 for a smooth steel surface and as high as 0.80 for a rough steel surface. Pressure influenced the measured coefficients of friction, and lower normal pressures yielded higher coefficients. The influence of fiber angle was observed to be moderate, although clearly detectable, thereby resulting in a higher coefficient of friction when sliding perpendicular rather than parallel to the grain. Moist specimens contained higher coefficients of friction than oven-dry specimens. The results provide realistic values for practical applications, particularly for use as input parameters of numerical simulations where the role of friction is often wrongfully considered. Keywords: laminated veneer lumber (LVL); wood; static friction; high pressure; angle-to-grain; moisture content
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Introduction
Friction is experienced in our daily activities, and its presence is typically unnoticed compared to its absence, for example, in slippery walkways or roads. However, in engineering practice, particularly in mechanical engineering, friction causes significant wear of machinery parts or higher energy consumption. Therefore, reducing friction using appropriate methods, such as suitable lubrication or surface treatments, is often desirable. Although friction is encountered regularly in structural timber engineering, it is not considered explicitly in design. It occurs in conventional connections between the members (e.g., tenon joints)
and in connections with metal fasteners (e.g., doweltype connections or nails). Hirai et al. [1] reported effects of friction in timber constructions. The influence of dowel roughness (frictional behavior between the dowel and the surrounding wood) has been studied experimentally, and high variation of the load-bearing behavior and ultimate loads has been observed [2, 3]. The influence of friction on the connection behavior is obtained by numerical simulations. Parametric studies clearly show the increase in contact area when high friction dowels are used a
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