Abstract
Knowledge of friction coefficient of agricultural commodities on various structural surfaces is imperative in the design and material selection for postharvest handling, transportation, processing and storage equipment. This paper presents the friction coefficients of local food grains on different structural surfaces as a function of moisture content. The experiment was conducted using a Complete Randomized Design (CRD) in a factorial treatment design to evaluate the influence of different structural surfaces (glass, mild steel, plastic, ply-board, and aluminium) and moisture content levels (6, 12, 18, and 24% wet basis) on the coefficient of friction of selected local grains (benniseed, finger millet, pearl millet, and hungry rice). Results obtained indicate that the friction coefficient (μ) of the studied grain samples increased linearly with increase in moisture level for all the tested structural surfaces. Within the range of the studied moisture content, benniseed exhibited the highest μ-value (0.526 ± 0.031 ≤ μ ≤ 0.784 ± 0.157) on ply-board, whereas hungry rice had the lowest value (0.248 ± 0.018 ≤ μ ≤ 0.527 ± 0.023) on glass material. Amongst the tested metal surfaces, aluminum had the lowest μ-value (0.236) at 6% moisture content. The effect of structural surfaces and moisture contents as well as their interactions on friction coefficient were statistically significant at P =.05 for all the studied grain samples. High values of correlation coefficient (R2) > 0.95 were obtained to indicate strong correlation between μ-values and experimental factors. A low coefficient of variation (CV) of 2.75% was obtained to show high experimental reliability.