Bionic Drag Reduction And Wear-resistant Theory And Techniques Of Subsoiler

Using bionic principle to solve practical engineering problems has become a majoradvancement in the developments of science and technology. The researchs and applicationsof modern bionics have permeated almost all fields of industrial and agricultural production,including field of agricultural machinery. Heavy wear and large tillage resistance havebecome two main technical problems which have not been solved well in the field ofagricultural machinery, especially for subsoiler, a typical agricultural soil-working part thathas big working resistance, high energy consumption, spear badly wear and short life. In thisstudy, the structural optimal design of subsoiler was performed in order to reduce tillageresistance and increase wear-resistance of subsoiler spear based on structural bionics andfunctional bionics means.Some shells of aquatic mollusks such as shells and clams show excellent wear-resistance performance although long-term abrasive wear by water sand in their livingenvironments. Pangolin, as a typical soil cave animal, its squama also has phenomenalcharacteristic withstanding repeated abrasive wear of soil and gravel during their activity andpredation process. The reason why these two organisms have such excellent wear-resistance,on the one hand they have wear-resistant material composition of tissues and organs, on theother hand may be microscopic or macroscopic geometrical structure on the surface of theorgans play a vital role in their performances. The abrasive wear form of subsoiler spear withsoil is extremely similar to wear-resistant organs of two organisms surface. In this study,Inspired by the relations between subsoiler and these two organisms, shell of chlamys farreriand squama of pangolin were established as the bionic prototype. After through the analysisof wear-resistant surfaces of these two objects, it was found that both shells and squama haveridge geometry structure with radial distribution. The outer surface ridge structure geometryinformation of these two research objects was extracted using Reverse Engineeringtechnology and then the outline coordinate points distributions of the cross-sectional of ridgestructure were obtained. According to the distribution of the coordinates, sine function curvewas selected to fit the coordinates and the fitting degree of approximation was evaluated thenthe fitting curve and fitting equation were obtained finally. The general form of fittingequation is: f (x)=asin(bx+c), the soil-engaging surface of subsoiler spear withwear-resistant bionic structure was designed. Based on the mathematical model, the functionof contour curve of ridge structure, which will be applied to the design of bionic structural surface of subsoiler spear, was final established as follows: f (x)=1.3sin(0.4x)based ontaking into account agronomic requirements of subsoiler spear in the practical workingprocess, meanwhile the manufacturing processes should be also considered. Finally, thebionic ridge stripe with the bottom width (D) of5mm and the high (H) of1.3mm wasdesigned. There are following three types distribution space of1D,1.5D and2D on thesurface of subsoiler spear and the length of the ridge stripe is equal with the width ofsubsoiler spear. Based on the above design scheme, two wear-resistant steel65Mn and T10were selected as the manufacture materials of bionic wear-resistant subsoiler spear samplesand the abrasive wear tests were carried out using bionic samples and general flat subsoilerspear samples in the abrasive wear testing machine, and then the mass wear losses were got.The analysis results of abrasive wear tests showed that the wear losses of all bionic ridgesamples are less than those of general flat samples under the same test conditions, and thereduction range is7.1%-44%which indicate the bionic ridge geometrical structure canimprove the wear-resistance of subsoiler spear obviously. The wear loss of the samples isincreased with the sliding velocity which demonstrate that the sliding velocity can influenceon the wear characteristics of samples significantly. The contrastive analysis results of wearloss for the same material samples showed that the wear losses of samples with distributionspace of1.5D are less than those of samples with distribution space of1D and2D, itdemonstrate that the distribution space of bionic ridge structure has significant impact on thewear-resistance of subsoiler spear and it is most conductive to improve the wear-resistanceof subsoiler spear when distribution distance is1.5D. The wear loss comparative analysisresults for the same type of samples which manufactured by different materials showed thatthe wear losses of T10samples are less than those of65Mn, it can be concluded that thewear-resistance of T10is higher than that of65Mn.This may provide theoretical basis forselection of manufacturing materials of subsoiler spear in the future.Utilizing bionics to reduce tillage resistance of subsoiler is another problem need solvedin this study.Some organs of natural creatures have excellent special features after millions of yearsof evolution, Such as a typical soil cave animal mus musculus which claw toes haveextremely high-efficiency soil digging functions. This may provide bionic reference foranti-drag structural design of subsoiler.In this study, the claw toe of mus musculus which has highly efficient digging functionwas took as bionic biological prototype, soil-cutting edge curve form of bionic subsoilershaft was designed in order to reduce the tillage resistance of subsoiler. The study found thattillage resistance of subsoiler mainly come from cutting soil action of soil-cutting edge ofshaft in the hard soil, therefore, reducing soil-cutting resistance of soil-cutting edge of shaftcould decrease the tillage resistance of subsoiler significantly. The previous study found thatthe upper surface contour on the longitudinal section of claw toe of mus musculus hasexponential feature, the fitting curve function is as follows:Y=66.61e0.0117X+17.78e0.1835X. The fitting curve of claw toe contour of mus musculus was applied to the curve structuraldesign of soil-cutting edge on the subsoiler shaft and the bionic anti-drag subsoiler withexponential feature was manufactured. The tillage resistance contrast tests were conducted inthe indoor soil bin using bionic anti-drag subsoiler, L-type suboiler, tilt type subsoiler andparabolic type subsoiler, respectively. The results of comparative analysis of tillageresistances showed that both tillage depth and forward speed have significant influence onthe tillage resistance of subsoiler. The tillage resistances of bionic anti-drag subsoiler withexponential feature are less than those of other three types subsoilers under the same testconditions and the decreased range is7.9%-58.7%, which indicate that the bionic anti-dragsubsoiler has obvious reducing resistance effect. The contrast tests were carried out inoutdoor field using traditional arc-shape subsoiler and bionic anti-drag subsoiler, thecomparative results of tillage resistances showed that tillage resistances of bionic subsoiler isobvious less than those of traditional arc-shape subsoiler under the same test conditions andthe decreased range is8.5%-39.5%, which gave more evidence that bionic anti-dragsubsoiler has excellent anti-drag property.The cross-section disturbance morphologies of topsoil were analyzed after tilling usingbionic subsoiler and traditional arc-shape subsoiler, the analysis results showed that thetillage layer morphology of bionic anti-drag subsoiler has characteristics of more narrowfurrow and less extent soil uplift which means that the bionic anti-drag subsoiler has slightdisturbance effect on the topsoil and it is more beneficial to soil water storage andpreservation ability after subsoiling. The synergistic anti-drag effect of bionic subsoiler shaftand bionic spear was analyzed by tillage resistance test in the indoor soil bin, the resultsshowed that the bionic subsoiler spears can reduce tillage resistance of subsoiler comparedwith traditional flat subsoiler spear under the same test conditions, the1.5D type subsoilerspear has excellent anti-drag effect among three types bionic subsoiler spears.Numerical simulations of subsoiling process of the bionic anti-drag subsoiler andparabola type subsoiler was performed based on discrete element method (DEM), the resultsof simulations showed that both the stress field and velocity field of the bionic anti-dragsubsoiler are significant less than those of parabola type subsoiler and the simulation resultsproved again that bionic anti-drag subsoiler has excellent anti-drag property.