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vol. 13, nr. 2 (2009)
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Method of measurement of coefficient of friction between pairs of metallic and organic objects
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Józef Łukaszuk, Marek Molenda, Józef Horabik, Joanna Wiącek
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Institute of Agrophysics, Polish Academy of Sciences, ul. Doświadczalna 4, 20-290 Lublin |
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vol. 13 (2009), nr. 2,
pp. 407-418
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abstract:
A method for determining the coefficient of friction between pairs of metallic and organic objects of approximately spherical shape was elaborated. The method consists of simultaneous determination of force of friction and relative displacement of pair of grains under normal load. The method was verified through measurement of friction between pair of steel plates and pair of steel balls of diameter of 5 mm. The optimal conditions ensuring high accuracy and repeatability were estab-lished. Coefficients of friction of objects made of steel, and pea, wheat and rapeseed grains at equi-librium moisture content were determined. In the case of rapeseed grains normal load equalled 0.59 N, while the normal load of 0.98 N for other samples was applied. The highest repeatability of results was obtained for steel plates. Repeatability was much lower in the tests where steel balls were used, which resulted from non-repeatability of contact conditions due to both inhomogeneous distribution of friction properties of surface and impossibility of repetition of load conditions. It was found that scatter of force of friction was the highest for pea, wheat and rapeseed grains due to variability of shape, roughness of surface and irreversible deformation in contact. The range of values of coefficient of friction should undoubtedly be presented in design standards and designers should adopt values reflecting conditions of operation.
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keywords:
inter-grain friction, coefficient of friction, internal friction angle, angle of repose
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original in:
Polish
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