Abstract:
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 crosssectional
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.
