Study on Material Characterization of Rape Stalk and Stalk Divider
|School||Hunan Agricultural University|
|Course||Seed Science and Engineering|
|Keywords||rape stalk silique mouth loosing stalk dividing finite elementanalysis dynamics field trials|
Rape is one of the most important oil crops which occupies an important position in China’s agricultural production. Rape mechanized harvesting is an important part during the production, while rape harvesting machine at present has an increase of cutting table harvest loss due to the stem cross. The tests of physical characteristics have been done on rape plants and siliques in harvest, using high-speed camera technology to analysis the siliques split in collision. The paper is to design a stalk divider and provide theoretical basis for the design of rape mechanized harvesting equipment, on the basis of kinematics and dynamics analysis in its structure, using Adams, Solidworks, MATLAB software to study the stalk divider, finally carrying out the structure analysis on the key components. The main results are as follows.1) The field characteristics tests of rape plants show that plant diameter around8mm is suitable for mechanized harvesting due to fewer branches, branches higher above the ground. Those characteristics are beneficial to harvest mechanization, cutter dividing and reduce the shattering loss in cutting station. Medium-density planting exhibits the stable average diameter, medium plant height, fewer branches, and higher distance above the ground which give more advantages for mechanized harvesting. The study on the silique tensile mechanical properties affected by maturity, ripening agent shows that:the rape diameter with medium-density planting is between8mm-10mm, its silique resistance to tension capacity has little impact on harvest period which can improve the utilization of mechanical operations and working time span; Ripening agent has little impress on the plant silique tensile strength. Spraying a ripening agent has a positive effect on rape which can be harvested ahead of time.2)The tests of anti-extrusion characteristics of rape stalk have been conducted in order to provide a suitable work parameters of extrusion points and extrusion height for sub-compartment design. The results show that:the snap angle of inclination is mainly distributed in the range of40°-60°,The effect of stalk extrusion is better with600mm height from ground,30°extrusion deflection, medium maturity, in which the ratio of rebound is less than20%, the unit extrusion pressure is less than0.25N.mm-13)Pco.1200high speed camera has been used to analyze the silique break process in rape harvest period. The result show that different collision direction, different locating place have impact on the silique break. Collision direction from bottom to top need relatively large velocity, while from top to bottom need less collision force. Upside down state needs minimum collision speed, natural state needs larger collision speed and horizontal state is maximum. Test of extrusion silique results show that the extruding force from side direction is larger than from front direction, which the squeeze pressure is relatively smaller with200mm/s extrusion speed.4)The stalk divider is systematically designed by "Black box" method. Using functional decomposition and principle scheme solution, then building morphological matrix calculation to obtain the reasonable structural principle program-reciprocating upward stalk dividing, thus the overall layout structure has been designed.5) Kinematics and dynamics analysis have been used in parallel four-bar mechanism and the geneva wheel mechanism. The study found that:while parallel four-bar mechanism were in reciprocation process, the thrust F on the horizontal slider to the left the force had larger value at first, then the force gradually decreased to a smaller value in a stable lower range with the increase angle; Due to mobile friction bearing a part of the boost force, the force was small while slider movement to the right, but change tendency is overall symmetrical. The angular velocity and angular accelerated velocity of geneva wheel analysis showed that the symmetry angle was0.83°in M shape; Relative velocity and acceleration analysis for cylindrical pin in the chute showed that the symmetry angle was0.83°in V shape symmetry distribution; Radial pressure from push rod to the chute change from-45°to the φ1angle of-10.62°, at the beginning of the process it had a gradual rise, then decreased sharply from-10.62°to0.83°to a lowest point, a symmetric cycle from0.83°to the forward angle increase, the whole process changed in M-shape.6)The structure optimization analysis has been taken on the key components of the stalk divider, which the slider length is62mm the force is minimum. In the case of not exceeding the maximum pressure angle, bothway thread spindle has been optimized that minimum base circle radius is14mm. The circumscribed circle radius of37mm is most reasonable for bothway thread spindle. The force curve is a parabola shape slider change about0.4%while slider ran after excessive arc. Finally, the structure optimization analysis has been done for the push rod of divider in two sides, on both sides of the lifter angle is60°,the best deformation length of the main push rod is855mm because the force is in the minimum state.7)Kinematics and dynamics simulate analysis on the key components of stalk divider has been taken with Adams software, the finite element analysis has been done on push rod and geneva mechanism by the Solidworks software simulation, the results are as follows:through kinematics analysis on the level of the top push rod,the velocity change fitted equation of mass center of push rod is:y=0.0015x2-0.2598x+15.112(R2=0.9996)Acceleration change fitted equation of mass center of push rod is:y=-0.0001x2+0.0107x-0.4963(R2=0.9964)The finite element simulation analysis has been done for push rod and geneva wheel:the static analysis and the fatigue analysis on push rod show that the original design of the structure and material is completely in conformity with strength requirements; and the finite element analysis shows that the maximum stress concentrates in the transition circular arc of the geneva wheel; the optimal thickness of the geneva wheel is4.44583mm,the thickness of side panel connect to cylindrical pin of driving lever is8.63324mm, after optimization the relative quality drop55.54%and32.08%respectively. Finally, the thickness of the geneva wheel gets rounded to5mm, driving lever gets rounded to9mm, cutaway disk gets rounded to5mm, cylindrical pin of driving lever gets rounded to14mm. 8)The field trials have been conducted for prototype, the results show that:1) the rising rate of push rod increases, the in line stability decreases.2)the loss rate of arc-shaped push rod is greater than the spherical push rod, while the consistency and stability has no significant effect.3) the results show that the total loss rate changes little in sequence and opposite lodging while loss rate increases significantly in the case of side direction lodging.4) the loss rate of early maturing variety is greater than medium maturation variety and medium maturation variety is greater than the late-maturing varieties, maturity has no significant effect on the in line consistency and stability.5) the broken branches rate increase with the rising speed of push rod, the impact is relatively small in sequence and opposite direction lodging, while the broken branches ratio of side direction lodging increases rapidly, the maturity has little effect on broken branches rate.6) three factors of the ascending velocity of push rod (A), the push rod shape (B), rape maturity (D), three performance indexes of total loss rate, in line consistency, in line stability are designed in orthogonal test. The range analysis of orthogonal test shows that the most important factors of the total loss performance is D, followed by B and A. The factor order is D> B> A, that is optimal combination push rod speed40mm/s, crop side lodging, late maturity. The influence of crop lodging performance to in line consistency is B> D> A in turn, optimal combination along is in sequence lodging of the crop, late-maturity, push rod speed100mm/s. The influence of crop lodging to in line stability is B> A> D in turn, the optimum level is A1,B1, D2respectively, the optimal combination crop is in sequnce lodging,40mm/s push rod speed, and medium maturity.7) variance analysis shows that the different levels of crop maturity have much influence on the total losses (P=0.014<0.05), while the push rod speed and lodging situation have no significant impact on the total loss. The influence of factors (A, B, D) to in line consistency and in line stability is not significant, but rape maturity is the main factor affecting the total loss from the P value. Rape lodging situation is the main factor that affects the in line stability and consistency, but the effect is not significant.