Study On Bionic And Resistance-reduction Of Stubble Crushing Blade Roller

Technology of giving stubbles back to soil is not only one of the kernel agricultural technologies in protecting-cultivation but also a key technology of ecological-agriculture, environment-protection-agriculture and green-agriculture. Large numbers of agriculture tools that can give stubble back to soil or joint operation equipments with working procedure to give stubble back to soil are needed in the vast area of North China. Because the operation of giving stubble back to soil can consume a big amount of energy, stubble crushing components are urgently needed for saving energy and lowering energy consumption. Supported by Science and Technology Development Plan Item: Bionic research on soil-touched component of joint operation machine for ploughing up the soil(Item number: 20050539), the main stubble crushing component was remodeled making use of modern bionic technology, then the targets of saving energy and resistance-reduction were reached.Modern bionic studies show that during long-term exchange of material, energy and information with nature, many animals have formed excellent body system adapted to the environment. Mole cricket was chosen to act as bionic research object of stubble crushing blade. In the course of long-term struggle with soil and crop stubbles, and through hundreds of millions of years of evolution, the excellent geometric shape and extremely optimized biomechanical function of legs of mole cricket are gradually formed. The legs not only can effectively conduct digging and cutting jobs but also have the function of antiadhesion and resistance-reduction. Through bionic analyzing the shape, form and structure of initiating leg and its toes, and conducting curve fitting to the contour of the toes we know that the initiating leg of mole cricket is non-smoothed and we get the math model of hackle toe contour. Through geometric analysis of the distribution of the toes on the leg, bionic geometric feature parameter of the hackle was obtained. Owing to the form of the toes and coupling function of the hackle structure, the initiating leg can cut soil and the stubble of crop with lower energy consumption and less resistance. This provides bionic principle for optimized design of stubble crushing components with high efficiency to reduce resistance and save energy. The paper takes L type stubble crushing blade as prototype to design bionic one. With regard to the detail dimension design, the common used triangle tooth hackle dimension and the geometric feature of the initiating leg of mole cricket were considered synthetically. Five types of bionic stubble crushing blade were designed, every tool angleφwas 50°, while throat angleθwere 0°, -15°, -22.5°, -35°and -50°respectively, the biquadratic fitting curve of the initiating toe of mole cricket was used to act as the two sides of every hackle.Stubble crushing roller is the main component of stubble crushing machine, it is made up of 4 blade disks with blades assembled spirally on each one. UG-NX was used in the paper to conduct parameterized design to stubble crushing roller. It is realized that the assemble angle of the stubble crushing blade to the blade disk will be computed fast and then the fix hole dimension of the stubble crushing blade disk will be designed after giving the stubble crushing deep, turning radius and rotate speed of the roller and the advance speed. Meanwhile, a dynamic relation was established between the value of the assemble angle and the kinematics parameters of stubble crushing machine set. Thereby, it is ensured that not only the tuning radius of the roller fits design radius, but also the blade back will not jostle or rub untilled soil. The dimension conjunction was set up between blade disk and blade of stubble crushing machine, then virtual assembly of stubble crushing blade roller was realized, and the interference-existence-check can be done through different view directions. After checking, parts of the designed stubble crushing roller in this paper have no interference. The result of kinematics simulation to stubble crushing roller and following up the key points of the blades shows that the simulation output is in accordance with theory analysis. This reflects the promptness and intuitive of parameterized design method for stubble crushing roller based on UG-NX, and provides a new design and analysis method for designing stubble crushing roller and correlative agricultural machines. In this paper, parameterized 3D model design also be conducted to the parts of the stubble crushing machine, the structure and dimension relationships in one part itself and among correlative parts were established and a parts library was set up thereby. The stubble crushing machine and the parts in the library can be easily transferred into 2D drawings with UG-NX, then the 3D entities and the 2D drawings can be correlatively modified, and this ensures that the data of 2D drawings are in accordance with the data of 3D entities. So the efficiencies of the remodel-design and the series design of stubble crushing machine are greatly enhanced, and the high design accuracy is ensured.The stubble of corn is composed of the stalk up the earth surface and the root beneath the earth surface, while the root consists of primary root, secondary root and aerial root. Because of the complex kinematics performance of the stubble, it is difficult to simulate the real cutting condition, and the repetitiveness of the experiment result is poor. The stubble cutting experiment was decomposed into two parts: cutting stalk and cutting soil. The twisting moments and the force in 3 directions were obtained after the experiments. The bionic stubble crushing blade which had the best resistance-reduction effect was chosen after experiments with different blade types. The single-blade test-bed with self-developed stubble crushing roller was used to do experiments.First, the designed 5 bionic blades was in comparison with the prototype blade in the cutting stalk experiment. The result shows that the designed bionic blades of different type have a wide variability in resistance-reduction effects, there are two types of bionic blade which increased resistance. In general, for the same type of bionic blade, the resistance-reduction rate is high when it runs in low speed, and the resistance-reduction effect lowers while the rotate speed heightens. Beat and incision is combined in the process of stalk-cutting. When the machine runs in high speed, the interaction between the blade edge and the stalk is beat-major and incision-minor, and the hackle cut effect is unconspicuous. Because the prototype blade hasn't hackle at tangent edge, there are stalks hadn't been cut up in the process of the cutting stalk experiment when the roller runs in low speed, while the bionic blade could cut up the stalk. The reason of the difference is that the frictional angle between the tangent edge of the bionic blade and the stalk is increased when using bionic one, which makes the stalk can't slide away along the edge, until it is cut up. But the axial thrust load of the bionic blade is correspondingly bigger than that of prototype blade. Through experiment, we get best whole process resistance-reduction bionic blade, its throat angles are 0°,-15°,-22.5°.Then conduct soil cutting experiment. Carry out orthogonal test with 3 factors and at 3 levels: choose the 3 bionic blade types which can reduce resistance, rotate speed of stubble crushing roller, soil cutting deep and choose L₉(3⁴) orthogonal layout. The result shows that the best one is the bionic stubble crushing blade having a throat angle of -15°. After that, in order to know the primary and secondary factors which influence twisting moment and three-axis force, a L₉ (3⁴) orthogonal layout was designed and the best bionic blade was used to do the experiment. The result shows that the primary and secondary factors which influence twisting moment, that is, energy consumption: rotate speed of the roller, advance speed and soil-cutting deep. Then we know the optimized combination to influence the twisting moment, that is, to reduce energy consuming, is to augment radius of gyration of the roller combined with searching stubble crushing blade type of lower energy consumption. Meanwhile, we get the primary and secondary factors which influence the force of different axis when stubble crushing blade cutting the soil, the primary and secondary factors which influence the axial thrust load F_x: soil cutting deep, advance speed, rotate speed of the roller, the primary and secondary factors which influence the horizontal force component F_y: advance speed, soil cutting deep, rotate speed of the roller, while the primary and secondary factors which influence the vertical force component F_z: soil cutting deep, advance speed and rotate speed of the roller.On the base of dynamically analyzing the established finite element model of the stubble crushing blade, conduct 3 dynamic simulations separately to the proto L type stubble crushing blade and the bionic one. Firstly, cut stalk beneath earth surface and rotary till soil; secondly, cut stalk above earth surface solely; thirdly, stubble crushing blade goes into the soil and cut it. The three simulation parts go to the same end: using bionic blade can reduce energy consumption, this is in accordance with the trend of the test. Value simulation also indicates that there exists concentration of stress when the stubble crushing blade impulse the soil, so hackle shape should be avoided at the tip of the blade. The established dynamic value analysis method will provide reliable analysis and forecast for the design of stubble crushing roller with resistance reduction function.4 group of contrast trials in the field was carried out using bionic blade and prototype blade assembled on common joint operation machine for ploughing up the soil and the remodeled joint operation machine alternatively. Using common joint operation machine, when advance speed of the machine set is 0.89m/s, the twisting moment reduced 6.37% more with bionic blade than with prototype blade; when advance speed of the machine set is 1.16m/s, the twisting moment reduced 5.31% more with bionic blade than with prototype blade. Then using the remodeled joint operation machine, when advance speed of the machine set is 0.91m/s, the twisting moment reduced 10.02% more with bionic blade than with prototype blade; when advance speed of the machine set is 1.17m/s, the twisting moment reduced 6.08% more with bionic blade than with prototype blade. The results of the 4 in field trials all indicate that the resistance-reducing and energy-consumption-reducing effect can be realized with bionic blade, and they also shows that at the same work condition, compared with prototype blade assembled on common joint operation machine for ploughing up the soil, bionic blade assembled on remodeled joint operation machine can improve advance speed and decrease twisting moment. When tractor at its first gear, the advance speed is improved 1.97% and the twisting moment reduced 10.86%; while at its second gear, the advance speed is improved 1.65% and the twisting moment reduced 6.72%. It is clear that using bionic blade assembled on remodeled joint operation machine for ploughing up the soil can not only reduce energy consumption but also improve work efficiency.