| Twig cutting is the most labor-intensive process in the bamboo harvesting process.When pricking and slicing machine works,the twig-cutting power provided by the pressure roller is limited because the bamboo pole is hollow and the root of the twig is quite hard,and the twig cutting knife is an important tool in this process,the unreasonable structure of the knife blade will produce problems such as damage to the knife,poor feeding and excessive energy consumption.Therefore,a reasonable blade structure is essential for smooth cutting.The main findings of this paper are as follows.(1)The effect of the physical and mechanical properties of the twig and the knife on the cutting was studied.The mechanical analysis of the removal process during the operation of the picking and slicing machine was also carried out,including the mechanical analysis when the pressure roller breaks the bamboo pole and pulls it,and when the knife cuts the twig.Through the above mechanical analysis,it is determined that the main structural factors affecting the performance of the cutting knife are the wedge shape and angle of wedge.65 Mn of knife material,0.2mm of blade thickness and flat blade shape were identified by studying the physico-mechanical properties of the twig and the knife.(2)Using ANSYS/LS-DYNA,the cutting process with single and double bevel cutting knives with wedge angles of 14°,20°,34°,44° and 60° were simulated,and the effects of the bevel form and wedge angle on the V-M stress,cutting resistance and the energy consumption were obtained,which were consistent with the theoretical analysis.According to the research objective,the maximum V-M stress and energy consumption are used as the evaluation index of the cutting effect.By comparing these 10 sets of finite element simulation results,a safety factor of 3 was taken,and the one with the maximum V-M stress not exceeding the allowable stress and the smallest energy consumption was selected among the 10 different structures of the knives.The maximum V-M stress is located within the 2mm radius of the knife blade,and the value is 241 MPa,the average cutting resistance is 61.14 N,and the energy consumption is0.331 J.This provides theoretical support for the subsequent optimization.(3)The results of the simulation are trained by BP neural network algorithm combined with genetic algorithm,and a prediction model is established to derive the energy consumption and V-M stress for single and double bevel knives with the wedge angle range of14°-60°,and to derive the optimal solution instead of finding the optimum in only 10 sets of knives.After rounding,the above algorithm results in an optimal combination of solution parameters in the form of a wedge angle of 30° and a single bevel.Then,based on this combination of parameters,the knife structure is optimized according to the stress concentration range for the bevel structure,and the structure is obtained as follows: single bevel,first wedge angle of 30°,second wedge angle of 10°.And take it as the final optimized results.Compared with the unoptimized 34° single bevel cutting knife,its energy consumption is reduced by 36.56%,and the maximum V-M stress of the knife is only 302 MPa,which meets the material safety strength requirement.(4)Carry out prototype tests.With the evaluation indexes of the flatness of the break side of the twig,bamboo speed loss and recovery,it was concluded that the flatness was improved by about 27%,the maximum speed loss percentage was improved by about 20%,and the maximum speed recovery time was improved by about 39% compared with the unoptimized knife during the cutting process with the participation of the optimized knife.The validity of the optimized design results was verified. |
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