Effect of Knife Velocity on Cutting Energy and Efficiency during Impact Cutting of Sorghum Stalk

A laboratory test-rig consisting of a pendulum-like oscillating arm was designed and fabricated for measuring cutting energy requirement and cutting efficiency on sorghum stalk. The sorghum stalk was fixed in a stalk holder to simulate a free-standing stalk in the field. A blade, sharpened at 30% bevel angle, was attached to the lower end of the arm which cut the stalk at 90 o to the stalk axis with knife velocities up to 8.5m/s. The experiment was conducted during cutting of sorghum stalk base (20 mm) and stalk height (120mm) above the ground level. The results showed that there was high correlation p≤0.1 between knife velocity, cutting energy requirement and cutting efficiency. Cutting energy requirement showed negative linear correlation with knife weight and stalk moisture content with cutting efficiency showing positive linear correlation with the parameters. The minimum cutting energy requirements for 20 and 120 mm were 7.87 and 12.55 Nm respectively, at corresponding knife velocities of 2.91 and 3.54 m/s. The maximum cutting efficiencies were 98 and 97% at 5.2 and 7.3m/s knife velocities, respectively.