Design and experiment of V-L shaped smashed straw blade

Abstract: A smashed straw blade with V-L shaped for smashed straw machine was designed based on analyzing the advantages and disadvantages of existing blades, such as straight-knife shaped, Y or L shaped and hammer shaped. It can solve the problems in practical operation, such as obvious abrasion, fierce machine vibration, unsatisfied smash effect and poor stability. We improved L shaped blade by adding a V-bending to form V-L structure. The V-L structure can decrease the included angle between edge line and ground to avoid wear too fast, extend the length of edge line to reduce blade density, move the barycenter outward to increase rotational inertia and ensure the barycenter located in the same plane with blade handle to improve rotation stability. The barycenter position was not affected by blade thickness, the blade mass increased and the deformation decreased with increase of blade thickness based on finite element analysis by Inventor software. To increase rotational inertia and prevent the deformation of blade, we confirmed the blade thickness was 8 mm. The maximum deformation was 0.16 mm and the minimum safety factor was 6.86. To offset the sliding cutting angle when the blade turned backwards, the forward inclination was designed. It was determined between 10° and 15° via the soil-bin test. The material of blade was 65Mn and the edge angle was 30°. Autogenously grinding edge was designed by medium-frequency hardening of edge. The working parameters of blade were determined based on analyzing the influences of tractor forward speed, roller revolving speed and interaction between them on straw smashing rate. The test results showed that the straw smashing rate decreased with increase of tractor forward speed and increased with increase of roller revolving speed. As for the interaction between tractor forward speed and roller revolving speed, straw smashing rate increased with decrease of forward speed and increase of roller revolving speed. The optimal combination was that the forward speed was 1 m/s and the roller revolving speed was 1 400 r/min by using the Origin software. The experiment of two factors and three levels was conducted taking forward speed and roller revolving speed as experimental factors, straw smashing rate as experimental indices. The optimal combination was that the forward inclination was 10° and the included angle between edge line and ground was 14° based on the range analysis and variance analysis. The interaction between forward inclination and included angle between edge line and ground was not significant. The blade cutting width of 89.8 mm and the gyration radius of 170.6 mm were determined according to included angle between edge line and ground. The field test was conducted to verify the operation effect of smashed straw machine. The qualified rate of straw smashing length between and in the ruts was 93.43 % and 95.35 % respectively, the average stubble height was 61 mm, the unevenness of straw dispersal was 14.7 % and the pure productivity was 0.48 hm2/(m·h). The test results showed that the smashed straw machine can meet the requirements of national standards. But the vibration performance and power consumption of smashed straw machine need to study further. The study can provide a reference to design the smashed straw blade.