Effect of loading rate on mechanical properties of rice (Oryza sativa L.) straw

This research was conducted to evaluate the effect of loading rate and internode position on the mechanical properties of rice straw in terms of shear strength, shearing energy, bending strength and Young's modulus. All experiments were conducted at the Department of Agricultural Machinery Engineering, Faculty of Agricultural Engineering and Technology, University of Tehran, Karaj, Iran, in October 2009. The properties were determined at three loading rates: 5, 10 and 15 mm/min and three internodes: the first, second and third internodes. The results showed that the loading rate had only effect on the bending strength. Furthermore, the internode position had significant effect on the shear strength, shearing energy and Young's modulus, and did not have any significant effect on the bending strength. The average shear strength was obtained as 12.18 MPa varying from 8.45 to 20.22 MPa, while the average shearing energy was calculated as 191.34 mJ ranging from 101.31 to 256.02 mJ. The average bending strength was obtained as 7.98 MPa varying from 6.70 to 9.81 MPa, while the average Young's modulus was calculated as 0.66 GPa ranging from 0.21 to 1.38 GPa. The information on the engineering properties of rice straw can be useful for designing the equipment used for harvesting, threshing, and processing.