Fundamental Studies on the Horizontal Screw Type Blade

Soil Pressure on the Surface of a Blade and Cutting Resistance

Abstract

The magnitude and distribution of soil pressure exerted on the surface of horizontal screw type blade were experimentally examined and the theoretical equation for cutting resistance was derived.
(1) The variation of soil pressure during one revolution of the blade was measured miniature load cells attached to the blade. The soil pressure at the joining point (A) of the vertical cutting blade and the cutting blade wass largest among five measuring points, and the time during which soil pressure was exerted was also longest. The variation of cutting torque almost agreed with the magnitude of soil pressure at the point A.
(2) In case of sand with small cohesion, the distribution of soil pressure was the same as that described above, but the torque was nearly constant.
(3) In case of the semi-infinite cutting width, the soil pressure on the turning blade turns out to be extremely large. The cutting action under this condition may occur actually, and attention must be paid regarding the strength of the blade.
(4) The soil pressure exerted on the surface of the blade was large on the cutting blade, and among others, it showed the largest value at the joining point of the vertical cutting blade and itself, while it was extremely small at the points C and D. Also the wave forms of the soil pressure and the torque corresponded. From the reasons described above, it was concluded that the cutting resistance of a blade is produced by the tip of the cutting blade, and the main factor is the shearing resistance of soil. Consequently, the theoretical equation for the cutting resistance was derived, assuming two dimensional cutting under the revolution at a fixed position. The tiling power and the forward component force agreed with the experimental values.