Research On Mechanism Of Corn Stalks Rind-pith Separation By Coupling Different-directions Forces

At present,corn stalks are widely used in industry,agriculture,catering and other fields.The cellulose-rich husk is used to produce paper,wood-based panels and disposable tableware.The rind has a large content of protein and nutrients,and can be processed into livestock feed and raw materials for ethanol extraction.Hence,using the husk or rind of corn stalks alone is beneficial to improve the added value of stalk resource utilization and promote the process of diversified utilization of corn stalks.In order to improve the rind-pith separation rate of corn stalks and promote its high-value utilization process,this paper takes corn stalks as the research object,explores the mechanism of corn stalks rind-pith separation by coupling different-directions forces designs a test bench of corn stalks rind-pith separation by coupling different-directions forces,and optimizes the process parameters of corn stalks rind-pith separation.The main contents and conclusions of the research are summarized as follows:（1）Detection of material properties of corn stalks.The moisture content of the whole corn stalk from internode 1 to 7 of natural drying for 45 days is 19.69%to 10.52%;with ascending of sampling location,the moisture content of the rind,pith and stalk decreased gradually.The average diameter of corn stalks in internode 1～7 is 28.22mm;the average height of the whole stalks is 188.28mm.The sampling location of corn stalk has a significant effect on the density of the pith and rind;the pith and rind density decreased with the increase of sampling location,the decreasing speed of pith gradually slows down,however,the decrease of rind shows a slow-acute-slow trend.The sampling location has a very significant effect on the thickness of corn stalk rind;The average thickness of the rind between 1 to 7internodes of corn stalks is 1.06 mm,and the variation range is 0.52 to 1.42 mm.（2）Mechanism analysis of corn stalks rind-pith separation by coupling different-directions forces.The single factor test is carried out and analyzed by F-value test method,taking the sampling location of corn stalks as the test factor,the deformation coefficient（longitudinal,transverse,average of longitudinal and transverse）and the difference of deformation coefficient between rind and pith（longitudinal,transverse,average of longitudinal and transverse）as the test indexes.The results show that the significant deformation coefficient difference exists between the same sampling location ringlike rind and pith,meanwhile,when ringlike rind and pith are under Y-direction pressure,the ringlike rind deformation is larger than pith deformation in the x-direction of the stalk cross section,which provides a theoretical basis for the corn stalks rind-pith separation by coupling different-directions forces.Using ABAQUS/explicit dynamics explicit solver and central difference solving method,Simulating the working condition of corn stalks rind-pith separation by coupling different-directions forces and analyzing the effect of that.The results show that during rolling in Y direction,due to the difference of X-direction deformation caused by different deformation coefficients between ringlike rind and pith of corn stalk,the x-direction cohesive between ringlike rind and pith failure is about 1/3 around of pith;after rolling,the rebound displacement of ringlike rind in Y direction is larger than that of the pith,resulting in the failure of the cohesive element in Y direction for nearly 1/3 around of pith;The stalk is subjected to the x-direction coupling pound-cutting force（component force）by coupling effect of pound-cutting with different-directions rolling compaction,and the separation effect of the segmented rind-pith is remarkable;the simulation results show that the anisotropic coupling force and the difference in the deformation coefficients of the corn stalk ringlike rind and pith make the corn stalk rind-pith separated efficiently.The force analysis of stalk under the pound-cutting with different-directions rolling compaction shows that the coupling rind-pith separation structure of pound-cutting with different-directions rolling compaction makes corn stalks be subjected to coupling force of pound-cutting with different-directions rolling compaction and realizes rind-pith separation.（3）Test bench design of corn stalks rind-pith separation by coupling different-directions forces.Based on rind-pith separation mechanism,the blade curve is designed as an Archimedes spiral with an uni-sliding angle,which can achieve a constant push angle during the shearing process;the blade with a clam blade that angle variation range is 15°to 30°and a thickness of 5mm have obvious hammering effect;the rind-pith separation effect of corn stalks is good when the applicable range of blades sliding angle,the rotating speed of the disc knife,rotating speed of double rollers is 36°～46°,449.38～935.44r/min,226.37～418.25r/min respectively.The joint simulation analysis based on Abaqus and N-Code finite element analysis software shows that the first 2 natural frequencies（X and Z directions）of the test bench are relatively close to the excitation frequency of the motor,and the maximum amplitude is 2.5mm,but the fatigue life of the test bench vibration in all directions All meet the requirements,the resonance of the test bench will not cause vibration fatigue damage;when the cutting blade is subjected to the ultimate load,the stress concentration occurs at the bolt hole and the contact between the blade and the stalk,where the maximum value of Von-Mises stress is 42.82MPa,which is less than the material yield strength of 345MPa,and the fatigue life of the blade is 5×10¹²times,which is higher than the elastic limit high cycle fatigue,therefore blades stress fatigue strength meets requirements（4）Optimization of technological parameters by rind-pith separation test of corn stalks.Through the shearing characteristics test analysis of corn stalks,it can be seen that the order of the influencing factors on the internode and node critical shearing strength are moisture content>sampling location>shearing speed and sampling location>moisture content>shearing speed;the corn stalks with a moisture content of 15%has lower shearing strength and higher shearing stability.Through the analysis of the peeling strength test of corn stalks,it can be seen that the order of the influencing factors on the adhesive strength is sampling location>moisture content>peeling speed;the rind-pith peeling strengths of internode sections among 1st-7th internodes of corn stalks are smaller and more favorable for mechanical separation for stalks with moisture content of 15%～20%.Orthogonal regression combination test is used to optimize the technological parameters of corn stalks rind-pith separation taking cutting disks rotation speed,peeling rollers rotation speed and blade sliding angle as test factors,stalk rind-pith separation rate as test index and corn stalk of 1-7th internodes with moisture content is 15%±5%as research object.Results show that the cutting disks rotation speed and blade sliding angle have significant effect on the stalk rind-pith separation rate;the significance sequence of influencing factors is blade sliding angle>cutting disks rotation speed>peeling rollers rotation speed;maximum corn stalk rind-pith separation rate is 88.264%and the corn stalks is cut ito segments with average length of 27.4mm that meet the actual production demand after the rind-pith sepration under the optimal technological parameters combination of cutting disks rotation speed is 449r/min,peeling rollers rotation speed is 226r/min and blade sliding angle is 46°.