Determination of some Selected Engineering Properties of Bambara Nut (Vigna Subterranea) Related to Design of Processing Machines.

Abstract

Bambara nut (Vigna subterranea (L) Verdc) is a major source of vegetable protein in sub-Saharan Africa. The aim of this study was to determine some selected Engineering properties of Bambara nut. Fresh Bambara nuts were bought from Kure market, Minna, Niger State, Nigeria. The pods were cleaned and sorted, and the pods manually cracked using stone to hit the pods on a flat concrete surface. The unharmed nuts were then selected and oven dried and the moisture content determined and calculated to be 14.05%. This study was carried out under approved standard laboratory conditions using standard engineering methods and instruments. Selected physical and mechanical properties of Bambara nut were determined and the values obtained are as follows: the average length, width and thickness, weight, geometric mean diameter, arithmetic mean diameter, surface area, sphericity, volume and density were 1.76mm, 1.45mm, 1.22mm, 1.70g, 1.46mm, 1.56mm, 6.69mm2, 82.85%, 4.14mm3, 0.04g/cm3. The principal dimensions varied with increase in moisture content, though there was no significant change in the major diameter. The coefficient of static friction was highest for galvanized steel and least for glass. From the values obtained, it appears that the increase in size of Bambara nut may aid a decrease in coefficient of static friction. The force required to fracture and compress the biomaterial (Vigna subterranea) were 12.5N and 27.75N on axial loading and 7.25N and 22N on longitudinal loading respectively.