| Xinjiang is an important walnut production base of China,but walnut utilization rate is very low,and walnut cracking is still carried out manually,although there are some simple equipment for cracking walnut,there still no mature products appeared in the market owning to the processing scale,low rate of high kernel and low cracking efficiency,which greatly limits the development of walnut industry.According to the processing-utilization status of Xinjiang walnut and problems existing in walnut cracking machine,the Wen-185 walnut were selected as research object in this paper,and the cracking theory and equipments of walnut were studied.Based on the summary of walnut researches at home and abroad,firstly,theoretical analysis and simulation studies of walnut were carried out;Then,combing with the advantages of manual and mechanical methods for walnut cracking,a kind of walnut cracking machine with impact extrusion type was designed and developed from the aspect of bionics,and the performance tests of prototype were conducted and the related index parameters were also given.The results can provide references for the study on the mechanism and equipment of walnut and other nuts.Main research contents and conclusions are as follows:(1)The geometric parameters of Wen-185 walnut were measured and analyzed,and results showed that the average value of sphericity coefficient and shell thickness is 0.91 and 1.53 mm,respectively,which indicated that walnut can be simplified into isotropic homogeneous thin spherical shell to deal with when to be forced;A theoretical analysis of walnut cracking were conducted based on the thin shell theory,and it is concluded that the best concentrated force is 2 pairs,and the impact extrusion head with V type structure was primarily designed;Through the finite element analysis of walnut cracking with flat and V type compression plate,the V type plate is more conducive to crack shell than flat head,and the results are consistent with the theoretical analysis;Based on fracture mechanics theory,the stracture of compression plate is ultimately determined to be the V type structure with tooth profile.(2)A kind of walnut cracking machine with impact extrusion type combing the walnut grading with cracking shell was designed and developed,which is mainly composed of a machine frame,a motor,a feed hopper,grading device,conveying device,cracking shell device,recycling cover and other parts.The structure and parameters of main components for cracking machine were designed,size classification range of grading device was determined for 32~48 mm,four section length of grading sieve cage were 270 mm,216 mm,162 mm and 108 mm,respectively,and the calculation speed of grading sieve cage is 28 r/min,and the length of bionic pressure rod is 510 mm,angle of V pressure bar is 30 degrees,the angle and thickness of V type blade with cracking head is 120 degrees and 4 mm,respectively,and so on;The basic parameters of Geneva mechanism were determined,and the grading device with transmission ratio of 2.43,three transmission ratio of cracking shell device was 17,2 and 1,respectively.(3)The test and performance analysis of prototype were conducted,the results showed that the optimum parameters for walnut classification was as follow: the opening size of feed hopper was 70 mm,speed of grading cage was 26 r/min,and inclination angle of grading cage was 1.5°,and the grading effect of walnut is up to 91.67% under the optimum parameters;walnut cracking test showed that the average value of walnut cracking rate and high kernel rate was 92.8% and 88.72%,respectively,which indicated the prototype has a high processing efficiency and high kernel rate;the processing efficiency of prototype was64.07 kg/h,more than 15 times the artificial processing efficiency,which could reduce the labor intensity and save labor costs,so it has a very good application prospects. |
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