Physical and Mechanical Properties of Alfalfa Grind as Affected by Particle Size and Moisture Content

Physical and mechanical properties of alfalfa (Medicago sativa, L.) grind are required for optimum design of equipment used in transporting, processing and storage of the material. This study was conducted to determine the effect of particle size (2.38, 3.36 and 4.76 mm) and moisture content (8, 9.3 and 11% wb) on some physical and mechanical properties of alfalfa grind. These properties include: geometric mean diameter, bulk density, coefficient of static friction (on galvanized iron, Plexiglass, rubber and polished steel surfaces), filling angle of repose, coefficient of internal friction, cohesion, and adhesion to polished steel plate. The bulk density varied from 161.6 to 202.2 kg m-3. The coefficient of static friction changed from 0.26 on polished steel plate to 0.87 on rubber surface. Larger particles with higher moisture content had the highest filling angle of repose (54.5°). The coefficient of internal friction varied from 0.64 to 0.88. The 2.38-mm alfalfa grind at moisture content of 11% (wb), and the 4.76-mm at moisture content of 8% (wb) had the highest and lowest cohesion (7.65 and 4.80 kPa), respectively. The adhesion on polished steel plate varied from 0.19 to 1.54 kPa.