Bending and Shearing Characteristics of Alfalfa Stems

M. Nazari Galedar, A. Tabatabaeefar, A. Jafari, A. Sharifi, S. Rafiee

Abstract


Bending stress, young’s modulus, shearing stress and shearing energy were determined for Alfalfa (Medicago Sativa L.) stem. The bending forces were measured at different moisture contents and the bending stress and the young’s modulus were calculated from these data. For measuring the shearing forces, the stem specimens were severed by using a computer aided cutting apparatus. The shearing energy was calculated by using the area under the shearing force versus displacement curve. The experiments were conducted at a moisture content of 10%, 20%, 40% and 80% w.b. The bending stress decreased as the moisture content increased. The value of the bending stress at low moisture content was obtained approximately 3 times higher than at high moisture content. The average bending stress value varied from 9.71 to 47.49 MPa. The young’s modulus in bending also decreased as the moisture content and diameter of stalks increased. The average young’s modulus ranged from 0.79 to 3.99GPa. The results showed that the shearing stress and the shearing energy increased as the moisture content increased. The maximum shear strength and shearing energy were found to be 28.16 MPa and 345.80 mJ, respectively. Both the shearing stress and the specific shearing energy were found to be higher in the lower region of the stalk due to structural heterogeneity.

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