INTERACTIONS BETWEEN WHEAT AND A CORRUGATED STEEL SURFACE

Friction of wheat on a corrugated galvanized steel surface was measure d using a direct shear apparatus for three moisture contents [11.9, 14 .2, and 17.7% w.b. (wet basis)] and four normal pressures (9.73, 34.05 , 70.53, and 94.85 kPa). The wheat samples contained in a transparent shear box were sheared across the corrugations. Movements of grain ker nels during shearing were recorded and analyzed using a computer image processing system. The coefficient of friction decreased with normal pressure in a pressure range from 9.73 to 70.53 kPa for all three mois ture contents. Changes in the coefficient of friction were less than 2 % for all three moisture contents when normal pressure increased from 70.53 to 90.85 kPa. Friction increased with the grain moisture content for all four normal pressures. Friction of wheat on corrugated steel was mainly grain-on-grain friction. An apparent shear plane existed sl ightly (2 to 5 mm) below the corrugation peaks. Grain-on-grain shearin g occurred in a zone extending from the apparent shear plane to about one corrugation depth above the corrugation peaks.