bending and shearing properties of safflower stalk

the research was conducted in order to determine the bending stress, young’s modulus, shearing stress, and shearing energy of safflower stalk as a function of moisture content and stalk region. 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 shear forces, the stalk specimens were severed by using a computer aided cutting apparatus. the shear energy was calculated by using the area under the shear force versus displacement curve. the experiments were conducted at four moisture contents (8.61, 16.37, 25.26, and 37.16% wb) and at three stalk regions (bottom, middle, and top). based on the results obtained, the bending stress decreased as the moisture content increased. the value of the bending stress obtained at the lowest moisture content was approximately 2 times higher than that of the highest moisture content. bending stress values also decreased from top to the bottom of stalks. the average bending stress value varied from 21.98 to 59.19 mpa. the young’s modulus in bending also decreased as the moisture content and diameter of stalks increased. the average young's modulus varied between 0.86 and 3.33 gpa. the shear stress and the shear energy increased with increasing moisture content. values of the shear stress and energy also increased from top to the bottom of stalks due to the structural heterogeneity. the maximum shear stress and shear energy were found to be 11.04 mpa and 938.33 mj, respectively, both occurring at the bottom region with the moisture content of 37.16%.