Research On Three-axis Working Resistances And Wearability Of Rotary Blade

Hand supporting rotary tiller is playing an important role in soil preparation.But now there are some problems such as high-power consumption,strong vibration of tiller and rapid wear of blade need to be solved immediately.The working resistances of rotary blade in horizontal,vertical and lateral direction are the direct cause of above problems.So,it is very crucial to study the change rule of three-axis working resistances,optimize the working parameters,and then improve the wearability of blade.This research will be helpful to popularize rotary tiller in hill areas and increase economic benefit of soil tillage.Firstly,physical and mechanics parameters of orchard soil in Guangdong province were measured,so as to clear the work environment characteristics of rotary blade.Secondly,taking C-type rotary blade for research object,the structural characteristics and motion trajectory of rotary blade were studied,the mechanical models of soil cutting were analyzed,thereby getting the working parameters which would influence soil cutting resistance.Thirdly,phase angle was used to characterize the contact state of soil and blade,the three-axis working resistances change rule of single blade in one soil cutting cycle were studied by experiments,the relationships between resistances and working parameters were discussed.Then working parameters were optimized with target of minimizing the three-axis working resistances.Fourthly,due to the existing defect that real time three-axis resistances of rotating blade cannot be measured by three-dimensional force sensor,the simulation model for interactive action between rotating blade and soil was established based on discrete element method,and then three-axis resistances of rotary blade could be accurately analyzed from microscopic view.Lastly,the maximum wear position of blade was found through wear test,and surfacing technology would be used to improve the wearability of blade.The main research results and conclusions are as follows:(1)Moisture content,hardness,density,particle size,shear strength and compression strength of orchard soil were measured and analyzed by experiments.The results provided a data basis for regulating soil in soil-bin and building the simulation model.And then motion trajectory and mechanical models of rotary blade were analyzed in theory.The results showed that cutting amount had relationships with structural parameters of blade,motion parameters and tilling depth.Soil cutting resistance and soil throwing resistance all had relationships with physical and mechanics properties of soil,structural parameters of blade.These conclusions could provide references for selecting the test factors and analyzing the motion of rotary blade in simulation model.(2)Phase angle was put forward to characterize the contact state of soil and blade,and then the change rule of three-axis working resistances in one soil cutting cycle were studied by experiments in soil bin.The results of orthogonal experiment showed that the primary and secondary order of the factors that affected forward resistance was tilling depth,working width,phase angle,bend angle and forward speed.Among them,working width and tilling depth had similar effect degree,bend angle and phase angle also had similar effect degree,and working width,and tilling depth had significant effect on the index.The optimal combination was bend angle of 120°,working width of 80 mm,tilling depth of 80 mm,phase angle of 60° and forward speed of 0.3 m/s.The primary and secondary order of the factors that affected vertical resistance was bend angle,tilling depth,phase angle,working width and forward speed.Bend angle,working width,tilling depth,and phase angle had similar effect degree,and also had significant effect on the index.The optimal combination was bend angle of 100°,working width of 80 mm,tilling depth of 80 mm,phase angle of 120°,and forward speed of 0.3 m/s.The primary and secondary order of the factors that affected lateral resistance was phase angle,tilling depth,bend angle,working width and forward speed.Tilling depth,phase angle and bend angle had similar effect degree,but they had no significant effect.The optimal combination was bend angle of 100°,working width of 80 mm,tilling depth of 80 mm,phase angle of 60°,and forward speed of 0.5 m/s.Making discussion about these results,and comprehensively considering the operation efficiency and energy saving,it was finally found that the best operating mode was bend angle of 120°,working width of 80 mm,tilling depth of 80 mm,and forward speed of 0.5 m/s in practice.(3)Simulation model for studying three-axis resistances of rotary blade was established by EDEM2.6 software.Experimental results in the soil bin showed that the practical measured values of torque had the same changing tendency as the simulated results.The changing rule of rotation shaft torque was that the value increased to a maximum from 0,then decreased to a minimal value gradually,and then increased to a high value fast,finally decreased again,which agreed with the actual working conditions of blades.Simulation for resistances of single rotary blade indicated that the horizontal resistance acted in the same direction to forward speed,the lateral resistance acted in the direction from inner face of blade to back,but the vertical resistance acted in the direction of down,and then up.The maximum values of horizontal resistance and lateral resistance both occurred at the maximum plowing depth,while maximal value of vertical resistance appeared when the blade turned about 30°.Comparing values of horizontal and vertical resistances with theoretical results and experimental results,it was found that they were the same change law with rotation angle of cutter shaft;meanwhile,the simulation values were more coincident with the experimental values.Finally,single factor simulation tests showed that the maximums of three-axis resistances increased with the increase of the rotation speed,when rotational speed was more than 250 r/min,the increase speed was faster.Maximums of lateral and vertical resistance slowly increased with the increase of forward speed,but maximum of horizontal resistance was in decline.Tilling depth had significant effect on three-axis resistances,so the greater the tilling depth,the bigger the maximums of three-axis resistances,and the power consumption would also increase sharply.(4)Wear tests were done in a rotation tester.The wear test results of common rotary blade indicated that the main wear positions were in edge of lengthwise area,edge of bend area and back of bend area.The wear started from cutting edge,and then extended to body.The metallographic analysis showed the order of bonding performance between surfacing coating and 65 Mn steel was as follows: Cr Mo coating>WC coating>BC coating>high-Cr coating.The results of hardness test showed that the order of coating layer hardness was as follows: WC coating>BC coating>high-Cr coating>Cr Mo coating>uncoated blade.The wear test results of coating blades showed that the order of wear-resisting performance was as follows: WC coating blade>BC coating blade>high-Cr coating blade>Cr Mo coating blade>uncoated blade.Field test proved that the method to improve the wearability of blade by adding continuous surfacing coating on the whole edge,and adding point surfacing coating on inner face and back of blade was feasible.The wearability of blade after surfacing treatment could be effectively improved than uncoated blade.