Preparation And Experiment Of Self-sharpening Blades With Gradient Materials Based On Computer Simulation Of Cutting Process

China’s modernization is inseparable from agricultural and rural modernization.Modern agricultural equipment is an important foundation for realizing China’s agricultural and rural modernization.The core material preparation and processing technology of key parts and components are an important factor restricting the development of modern agricultural machinery and equipment in China.Among them,the cutting blade,as a key part of crop harvesting machinery,directly affects the work efficiency and operation effect of the whole machine.At present,there is still a large gap in the preparation and processing technology of domestic blade materials compared with foreign countries.The development of new self-sharpening cutting blades to improve the reliability of domestic crop harvesting machinery has become an urgent problem in China’s implementation of rural revitalization strategies and the realization of agricultural and rural modernization.Therefore,in this paper,two methods of vacuum compound rolling and rare earth impregnation carbonitride-boron infiltration were used to prepare a rotary sharpener self-sharpening cutting blade.The microstructure,hardness,friction and wear properties of the two gradient material cutting blades were tested and analyzed.The mechanical characteristics of the cutting tool/stalk during the operation of the cutting blade was simulated by ANSY,the design of the cutting blade structure and motion parameters was optimized,and field tests were performed.The research contents and main conclusions are as follows:(1)Taking the rotary lawnmower as an example,the computer simulation of the cutting mechanism during the operation of an unsupported blade was carried out,the influences of the blade’s structural parameters and kinematic parameters(edge angle,edge curvature radius,cutting speed,cutter speed,etc.)on the mechanical characteristics of cutting were studied.The results show that the edge curvature radius and edge angle are important structural parameters that affect the sharpness of the cutting edge.During the cutting blade passivation cutting operation,the cutting effect on the stalk becomes weaker,the impact and drawing effects are enhanced,and the harvesting efficiency and operation effect become worse.(2)The mechanical and kinematic characteristics of the cutting blade to cut the stem were analyzed by finite element,and the formation mechanism of self-sharpening characteristics during cutter operation was discussed.The study found that the equivalent stress-strain value of the rake face gradually decreased from the cutting edge to the top surface during the operation.Therefore,the preparation of a gradient material with a high flank hardness and a uniform change in the rake surface hardness is the key factor in forming the self-sharpening characteristics,which is the theoretical basis for the preparation of gradient material self-sharpening cutters using multi-layer metal vacuum composite rolling(GCr15/Q420/IF)and rare earth impregnation carbonitride-boron infiltration.(3)The microstructure,hardness distribution and friction and wear properties of these two materials were examined and analyzed.The results show that the interface between different materials of the multilayer metal vacuum composite rolling blade is tightly bonded without macro defects and is in a metallurgical bonding state;The flank of the rare earth impregnation carbonitride-boron infiltration cutting blade is composed of a high-hard boride layer(thickness about 50-70 μm)and a carbonitriding layer(thickness about 0.8 mm-1.2 mm).The wear resistance of the two materials is better than that of the domestic blade materials,and the uniform gradient change of the structure,composition and hardness distribution is realized.(4)According to the national standard(GB/T1209.3-2009),the two gradient materials were processed into self-sharpening cutting knives(multi-layer metal rolling,carbonitriding and carbonitriding),the formation mechanism of self-sharpening characteristics was studied.The results show that the flank face has high hardness and good wear resistance;The hardness of the rake face changes in gradient,uniform wear during operation,small changes in the cutting edge angle and the radius of curvature of the cutting edge,ensuring the cutting edge sharpness at the cutting edge,thereby forming the self-sharpening characteristics during the cutting operation.The hardness of the rake face changes in gradient,wear uniformly during the operation,and the change of the cutting edge angle and the radius of curvature of the cutting edge is small,which ensures the cutting edge sharpness at the cutting edge and forms the self-sharpening characteristic during the cutting operation.(5)A field comparative test to cut alfalfa was performed by two kinds of self-sharpening cutting blade and a commercially available national standard cutting blade.The results show that the weight loss rate of the commercially available national standard cutting blades is about 2 times that of multilayer metal rolling cutting blades and 4 times that of carbonitride-boron infiltration cutting blades after 40 hours of cutting.The two kinds of gradient material cutting blades form self-sharpening cutting characteristics,with small structural changes at the cutting edge,and maintain excellent cutting performance for a long time;The alfalfa incision is flush,and the regeneration buds are less damaged,which is conducive to the healing and regeneration of the incision.