The Mechanism Of Reducing Soil Adhesion And The Design Of Bionic Plow

As a work supported by the Key Project of Chinese Ministry of Education (Grant No.02089) and the National Key Grant Program of Basic (Grant No.2002CCA01200), the very core of the paper is the discussion about the soil adhesion mechanism on the surface of plow moldboard and the designing, manufacturing and applying of the bionic un-smoothed plow moldboard.The paper sums up the up-to-date research achievements on interface adhesion between soil and plow moldboard to the theory of interface water film and the theory of interface absorbing. The former considers the main factor of producing soil adhesion is medium water between interfaces. The latter is the physical absorbing forces and chemisorptions. By analyzing the test of soil adhesive normal force and the model describing the interface of soil adhesion as five medium layers, a kind of interface draw test is designed which similar, but a little different, to the test of soil adhesive normal force. According to the results of the test, the cavities and the cavity negative air pressure in medium produce mainly the absorbing force between interfaces when drawing along normal direction of interface is found. The condition forming the cavities and the cavity negative air pressure in medium is that the absorbing force between medium and solid surface is greater than the combining forces between the medium molecules. This new discovery can be used to explain the principle of reducing soil adhesive force of the materials having a big water contact angle.The test snipping off lower part of capillary tube connects the phenomenon of cavities and cavity negative air pressure in medium with soil adhesion. When the lower part of the capillary tube snipped off, the water in capillary tube remainder represents a poised situation which bringing a question how the weight of water in remain capillary tube balanced. An analysis shows that, if the wall of the capillary tube remainder contacts the shearing surface with no clearances, the upper meniscus of capillary water will bring a kind of absorbing force same as the cavity negative air pressure. Connecting this phenomenon with that tillage means field soil cut by plowshare where abundant capillaries exist, the scene of how capillary water bringing soil adhesion in interface is described. The effects of the capillary negative air pressure absorbing action on soil movement course is analyzed in this paper, and the causation of the serious soil adhesion on the plow afterbody and the large area soil adhesion on the surface of the plow are explained too. The resistance to soil moving in the tangent direction of the surface of plow comes from frictional part and adhesive part. Friction and adhesion are the accrete behaviors in interface which having a different creating mechanism. A mechanical model on the interface of soil-plow is built according to the contact circumstances of soil on the surface of plow in the paper, which divides the soil moisture into four stages to discuss, the conclusions are gained that the resistances mentioned above are composed by the two parts from friction and adhesion respectively and the soil adhesion part is mainly made up of the capillary negative air pressure absorbing action and the physical absorbing forces and chemisorptions. By analyzing the trend changes of the frictional resistance and adhesive resistance along with the quantity of soil moisture, the trend changes of those are on the completely reversed directions have been known. Eventually the general equation of the tangent resistances of soil moving on the surface of plow is provided, which is a different one with that described by a synthetic coefficient and has an emphasis on the concept that resistance made up.There are some discussions about the principle of the tangent resistance produced in interfaces and its varieties when moving in the paper. Those discussions would give some helps to the studies such as the tangent movement on plane, the slide vibration and the perpendicular motion of plane.The theory of non-smoothe...