DETERMINATION OF SOME PHYSICAL AND MECHANICAL PROPERTIES OF HORSE EYE BEAN (mucuna sloanei) FROM SOUTH EASTERN NIGERIA.

Abstract

Selected physical and mechanical properties of horse eye bean (mucuna sloanei) were studied at different moisture content levels of 11.5%, 13% and 17% (db). Compression strength characteristics were conducted under quasi-static compressive force at longitudinal and latitudinal (lateral) loading positions and the rupture forces, compressive strength, modulus of deformability, toughness, stiffness and force at bio-yield point determined as the mechanical properties. Results indicated that volume (20.137 - 21.856 mm3), surface area (598.362 - 720.208 mm2), geometric mean diameter (24.98 - 27.12 mm), and weight (7.625 - 9.203 g) of the velvet bean seed increased linearly with increase in moisture content. Also, the bulk density, specific gravity (0.378 - 0.421 g/mm3), sphericity (0.882 - 0.831) and aspect ratio (0.974 - 0.726) decreased linearly with increase in moisture content. These indicate that Velvet beans have wide size ranges and no single sample of the grains can effectively represent the other. In the case of the force-deformation characteristics, result indicates that the force and corresponding deformation to rupture of velvet bean seeds were found to vary from 400N - 2500N and 3mm - 10.25mm in longitudinal loading positions and 800N - 2800N, 3.5mm - 11.5mm in lateral loading positions at the various moisture contents. The bio-yield force, compressive strength, stiffness and toughness of the velvet bean seeds varied from 400N - 1000N, 1.30N/mm2 - 8.03 N/mm2, 120N/mm - 833N/mm and 142.072 J/mm3 - 656.570 J/mm3 respectively in longitudinal loading positions to 600N - 2100N, 2.221 N/mm2 - 9.047 N/mm2, 57.14N/mm2 - 800 N/mm2 and 486.666 N/mm2 - 857.046 N/mm2 respectively in lateral loading position at the various moisture contents. Generally, the compressive strength of the horse eye bean seeds is higher at lateral loading position than at the longitudinal loading position.