Friction of Wheat: Grain–on–grain and on Corrugated Steel

Abstract

Coefficients of friction of wheat for grain-on-grain and on galvanized corrugated steel sheet were investigated using a modified direct shear apparatus. Tests were conducted under a normal pressure of 20.7 kPa using soft red winter wheat at a moisture content of 11.2% (w.b.) and an uncompressed bulk density of 740 kg/m 3. Three consolidation procedures and three methods of deposition of grain in the test chamber were used. Test results of grain-on-grain friction showed that consolidation procedure markedly influenced the force-displacement relationship, while its influence on the coefficients of friction were small. Shearing to peak strength as a consolidation method erased all effects of loading history and resulted in the highest values of the coefficient of friction. Grain-on-grain coefficients of friction were in a range from 0.47 + 0.007 to 0.56 + 0.004 depending on the method of grain deposition. Friction on two dimensionally different samples of corrugated steel sheet was examined using three methods of grain deposition. Corrugation depths were 13 mm on both samples, while their periods were 67.5 mm (short) and 104 mm (long). Coefficients of friction on the short-period corrugated samples were in a range from 0.42 + 0.0 to 0.46 + 0.004 and were significantly higher (a = 5%) than those on the long-period corrugated sample, which ranged from 0.36 + 0.003 to 0.39 +0.003. The method of grain deposition significantly (a = 5%) influenced the coefficients of friction of wheat on both types of corrugated steel sheet.

Mechanical properties of some granular agricultural materials used in silo design

“…Similar differences were observed by Rusinek and Molenda (2007) for rapeseed and by Ramirez et al (2009) when using the same types of surfaces with powdered agricultural products such as confectioner sugar and granulated sugar. Very small values (0.135±0.002) for the coefficient of friction between wheat and smooth galvanized steel were obtained by Molenda et al (2002a). However, these values were similar to those obtained herein for the steel surface using the square shear cell.…”

Influence of Steel Plate Roughness on the Frictional Properties of Cereal Kernels

“…According to numerous authors, including Molenda et al [12], Frączek [1], Horabik [13], Wiącek et al [4], and Królczyk [7], moisture content significantly influences the frictional properties of kernels. Changes in moisture content induce changes in the surface properties of kernels and endosperm properties [27].…”

“…Three groups of theories have been postulated: mechanical, molecular, and mechanical/molecular. According to the most accurate theories, friction is a phenomenon with a dual mechanical and molecular nature [1][2][3][4]12]. The most recent theory of friction has been developed by Frączek [1], who postulated that friction force has three components: deformation, adhesion, and cohesion.…”

“…According to the literature [1,3,4,7,12,13,[15][16][17][18], the following parameters should be taken into account in descriptions of seed-processing operations: seed attributes (maturity, moisture content, species, variety, shape variations), properties of the friction plate (type of material, roughness parameters), friction conditions (seed orientation relative to the direction of movement, sliding distance, presence of normal load), and environmental conditions (air temperature and humidity).…”

“…Frączek [1], Molenda et al [12], and Horabik [13] observed that the geometric structure of a surface and the roughness of biological materials influence the frictional properties of seeds. Despite the above, most researchers indicate only the type of structural materials, such as concrete, steel, or wood, without describing their manufacturing precision.…”