Optimization Design And Experiment Of Key Components For Small Cutting Machine Based On Low-damage-cutting Alfalfa-stem

Alfalfa is an important feeding raw material in animal husbandry,known as the"king of forage".With the improvement of the living standard of Chinese residents,the rapid development of animal husbandry will be promoted,and the demand for alfalfa will increase significantly,and the import volume will increase year by year.It is an important development direction to realize the high efficiency and low damage harvest of alfalfa to improve the yield of mu.At present,there are some problems such as low efficiency,long regeneration period and low yield due to serious damage of alfalfa stalk,which are directly related to the high quality development of animal husbandry in China.Based on this,this paper developed a small alfalfa low-damage cutting machine suitable for operation in hilly and mountainous areas according to the requirements of alfalfa harvesting.By measuring the mechanical characteristics of alfalfa stem and using the computer numerical simulation technology,the optimized design of the cutter was realized.The self-sharping cutter was prepared based on the rare earth carburizing,nitride and boron co-osmosis technology and the field experiment was carried out.The main research contents and results of this paper are as follows:(1)Through axial compression,radial compression,bending,shearing,density measurement and friction coefficient measurement and other related tests,the elastic modulus parameters and strength parameters of alfalfa stems,epidermis and thick-walled mechanical tissues,stem density(256.03 kg/m~3),dynamic and static friction coefficients of alfalfa and metal(dynamic and static friction coefficients are 0.511 and 0.427 respectively)and other performance indicators were measured,which provided data support for the establishment of alfalfa cutting simulation mechanical model and the reliability of cutting simulation.(2)According to the agronomic requirements of low damage cutting of alfalfa,the whole structure scheme of small alfalfa cutting machine was determined,and the working power,transmission system and operating parameters of the cutting machine were designed.The power of the cutting machine was 2.5 k W,the cutting width was 0.5 m,and the cutting height of the rotary cutter could be adjusted to 50 mm and 80 mm.To avoid missing cutting,select 3 pieces of cutter.(3)Based on the mechanical properties and cutting requirements of alfalfa stems,the two cutting methods of cutting knife,stem sliding cutting and cross cutting were compared.The statics and first-order modal simulation results of the cutter were analyzed,and the cutter strength and cutter speed were checked.The response surface optimization design of the rotation speed and forward speed of the cutter of the alfalfa cutting machine and the sliding angle of the cutter was carried out,and the optimization design of the cutter structure and low damage cutting working parameters of the small alfalfa cutting machine was realized:the rotation speed was 3000 r/min,the forward speed was 0.8 m/s and the sliding angle of the cutter was 20°.(4)A method for preparing self-sharpening cutters based on the two-stage heating method of rare earth catalytic carburizing-nitriding-boronizing process was established.Firstly,the cutters were carbonitrided at low temperature(600°C×8 h),then carbonitriding-boronizing at high temperature(800°C×6 h),oil quenched at 850°C and tempered at 200°C.The microstructure of the blade flank of the cutter is composed of a boronized layer and a carbonitriding layer.The thickness is about 800μm,and the maximum hardness can reach about1800 HV.It is verified by experiments that its wear resistance is 2.15 times that of the commercially available 65 Mn cutter,and it has self-sharpening performance.When the cutter is 20°sliding cutting angle,the wear resistance is better.(5)The field experiment results showed that the small alfalfa cutting machine met the agronomic requirements and efficiency indexes of low damage cutting,and the missing cutting rate was only 0.64%.Under the same cutting conditions,the damage degree of alfalfa was determined by the regenerated plant height after three weeks.Compared with the optimized alfalfa cutting machine,the cut damage of alfalfa cutting machine after optimization was reduced by 11.42%.