Study On Resistance Reduction Characteristic Of The Ripple-Lubrication Surface And Coupling Bionic

In the production of agricultural machinery and engineering machinery,the mechanical action is produced between soil component and soil,for instance breaking,cutting,turning,moving,etc.The interactions among soil and soil-engaging components lead to surface adhesion,friction and wear,and significantly reduce the terrain machineries work efficiency and quality.Therefore,it is imperative to put forward a new method and theory of reducing adhesion and drag force,and to design a high efficiency and low energy consumption soil-engaging components for terrain machineries.After a long period of natural selection and evolution,the soil animals have formed a perfect decreasing adhesion and resistance function.Such as earthworm that can freely move without clay in the underground wet soil environment.It can provide a way of thinking for soil-engaging components.In this paper,Taking an earthworm as bionic prototype,the anti-adhesion and drag reduction bionic studies of ripple-lubrication surface of earthworm were carried out.Pheretima aspergillum was used as research object,according to the motion characteristics of the earthworm,three kinds of body surface specimens were prepared,such as stretch,motionlessness and contraction.Based on reverse engineering technology,using the three-dimension laser scanner collected the point cloud data and obtained the morphology of earthworm ripple surface.On the basis of three different states of the earthworm body surface specimens,the bionic samples were designed.The discrete element simulation software was used to analysis the resistance reduction mechanism of earthworm ripple surface,from macro and micro point of views to seek the best corrugated surface structure.The simulation results show that the corrugated surface structures have excellent resistance reduction characteristics,at the same time,the contraction state surface is the best ripple structure.Compared to smooth sample,the forward resistance of corrugated surface is reduced by 16.97%,and the head of contractile sample bears the effect of earth breaking.Corrugated surface can decrease resistance by reducing the contact area of the soil,in addition,form naps with the soil contact interface.The contractile sample can effectively reduce the contact area by 15.65%.The turbulence of the corrugated surface to soil is greater than smooth specimen.The soil in ripple depression is pushed by ripple bulge,and the soil in ripple bulge is pressed by surface of sample.The more obvious the non-smooth is,the greater the disturbance is.the shrinkage specimen can not only improve soil structure,but also reduce forward resistance.Earthworm mucus ejected by dorsal pore is permeated into the surrounding soil which can provide a weak shear layer for earthworm motion.And this process can be seen as a fluid lubrication.The "shear thinning" rheological properties of mucus are important characteristic for the earthworm's lubrication drag reduction.To explore the effect of lubrication,a set of experimental equipment that can accurately control the velocity of lubricating fluid was manufactured and the optimal ripple structure and dorsal pore were processed to achieve coupling bionic.Experimental studies on earthworm lubrication show that the best position of 3 holes is the front holes of body(BF);the best position of 6 holes is the front holes of body and the back holes of body(BF+BB);the best position of 9 holes is the front holes of head,the front and the back holes of body(HF+BF+BB).In a comprehensive view,the front holes of body are more important lubricating position and the holes of body are better than the holes of head.Single factor test,orthogonal test and regression combination test were used to explore the effect and rule of advancing speed,lubrication flow velocity and positive pressure on drag reduction.A mathematical model was established to evaluate the drag reduction effect of the earthworm self-lubricating surface.The single factor shows that the influence of the lubricating drag reduction is obvious,increasing with the forward speed,the forward resistance reduces;the forward resistance decreases first,then maintains the value,as the lubricating fluid adds;The positive pressure is proportional to the forward resistance.orthogonal test shows that under the conditions of the positive pressure is 17 N,the forward speed is 300cm/min and the lubricant flow rate is 0.1 ml/s,respectively,the result of corrugation and self-lubrication of the earthworm resistance reduction is best.Meanwhile,the positive pressure is the most important influence factor.there is no interaction between the three factors.Finally the mathematical model of the forward resistance was built by Regression combination test.