measuring the static and dynamic cutting force of stems for iranian rice varieties

in order to help in the engineering design of rice harvesting machines, there is a need to have exact information concerning the physical and mechanical properties of rice stems. the cutting force for rice stems, therefore, was measured by designing and fabricating a static and dynamic shear test apparatus. the effects of moisture levels and the cross-sectional area of stem as well as the variety, blade bevel angle, blade type and cutting speed on shearing strength have been evaluated. the results indicated that the cutting force increased with an increase in the cross-sectional area and decreased with an increase in moisture content. the static and dynamic shearing strength was different among the varieties. the maximum and minimum shearing strengths were related to the varieties khazar and hashemi, with an average of 1629 and 1429 kpa for static test and values of 187.4 and 144 kpa for the dynamic test, respectively. the shearing strength decreased from 234.4 kpa to 137.4 kpa with an increase in blade cutting speed from 0.6 to 1.5 m/s. blade bevel angle and blade type had no significant effect on the shearing strength of rice stem.