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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.

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