Influence of moisture content and loading orientation on some mechanical properties of Mucuna flagellipes nut

Abstract

The effects of moisture content and loading orientation on some strength properties of Mucuna flagellipes nut namely, bioyield, yield and rupture points; bioyield, compressive and rupture strengths; and moduli of elasticity, resilience, toughness and stiffness were determined at lateral and longitudinal axial loading, using a Testometric Universal Testing Machine (UTM). In the moisture range of 3.38–10.7% (d.b.), bioyield, yield and rupture points of the nut decreased from 1,137 to 755 N, 1,157 to 790 N and 685 to 365 N, respectively, when loading was on the lateral axis, and increased from 1,090 to 1,888 N, 1,092 to 1,918 N and 420 to 1,215 N on longitudinal loading. Bioyield strength (1.83–1.41 N/mm<sup>2</sup>), compressive strength (1.85–1.44 N/mm<sup>2</sup>) and rupture strength (1.03–0.74 N/mm<sup>2</sup>), decreased with increase in moisture content under lateral loading, but increased from 4.05 to 8.17 N/mm<sup>2</sup>, 4.15 to 8.45 N/mm<sup>2</sup> and 2.6 to 6.3 N/mm<sup>2</sup>, respectively, as the moisture content increased in the above range, under longitudinal loading. The elasticity, toughness and stiffness moduli of the nut decreased (23–16.6 N/mm<sup>2</sup>, 0.615–0.525 J and 272.8–250 N/mm, respectively) with increase in moisture content under lateral loading, and increased (34.5–66.56 N/mm<sup>2</sup>, 0.508–0.69 J and 246–369 N/mm, respectively) with moisture content on longitudinal loading. On the above loading orientations, modulus of resilience increased from 0.166 to 0.355 J, and 0.255 to 0.576 J respectively, with moisture content. The properties were higher on the longitudinal than lateral axial loading. Second order polynomial equations relating these properties to moisture content were established.