大葱移栽机外文翻译
Trees Transplanting Machine Mechanics Model Establishment and
Shovel Blade Finite Element Analysis
Jie Zhou a, Zhipeng Li b, Qiang Huo c
Northeast Forestry University, Harbin 150040, China
a [email protected], b [email protected], c [email protected]
Keywords: trees transplanting machine, shovel blade, mechanics model, finite element analysis. Abstract. As shovel blade is the main working part of a trees transplanting machine, its design greatly affect the quality of the work conducted by the machine. In the research reported in this paper, the stress and strain analyses of the shovel blade were conducted. To carry out the analyses, the mechanics model of the machine was established first, then a three-dimensional model was built within Pro/E, and the blade’s static mechanics was analysed using ANSYS. With the results obtained, the maximum working pressure of the slave blade was finally identified , to satisfy the requirements of actual working conditions.
Introduction
Trees or small saplings are often required to be transplanted to other places due to the modern city construction, environmental transformation, forestation, etc. To use human resources to transplant results in high labor intensity, low efficiency, and high cost. In order to satisfy the requirement of the market, a kind of trees transplanting machine with simple structure and high efficiency has been applied to dig holes, place seedlings and transplant [1]. A machine of high-automation is desirable in order to meet the demand for mechanical transplantation of the afforestation seedling. The depth and ball diameter of soil are determined according to the diameter at breast height of the trees. Statistics show that tree transplant with the machine, the survival rate of forestation is 95% or above. Compared with the traditional afforestation technology the application of the machine shortens seeding period of 2-3 years, increases the rate of trees growth to 57.7%, and improves economic efficiency to 98% [2]. Because the shovel blade is the main working part of a trees transplanting machine, its design greatly affect the quality of the work conducted by the machine. In order to enhance the quality of the shovel blade design, this research established the mechanics model of the tree transplanting machine and carried out the finite element analysis of the shovel blade to predict its maximum working pressure.
Structure and working principle
The trees transplanting machine mainly consists of main frame, lift frame, supporting frame, shovel knife, and connecting and hydraulic mechanisms. Its overall structure is shown in Figure 1. The notations used in the figure are as follows: ‘1’, the tree; ‘2’, shovel blade; ‘3’, a shovel lifting lever with a sliding slot sword; ‘4’, supporting frame; ‘5’, supporting frame connected to the structure; ‘6’, shovel knife; ‘7’, ground; ‘8’, foundation platform; ‘9’, the rotation axes; ‘10’, overall lifting devices of shovel knife with hydraulic control ; ‘11’, overall lift sword of shovel sliding channel.
The shovel blade of trees transplanting machine is located in the opening-closing state in the front of the shoveling trees. The left three slices of shovel blades and the right three slices of shovel blades are open with a certain angles, and move along the transplanting machine toward the trees. After the shovel blade moves slowly to surround the tree, the shovel blade closes slowly and moves downward, and then penetrates the ground to reach the deep soil . The edge is closed when the cutting of a full root ball of the directed globular is complete, which is similar to cutting watermelon skin. The digging of each piece of shovel blade is controlled by the shovel blade lifting lever moving along the sliding slot of the fixed frame. All of the movements are controlled hydraulically.
Fig. 1 Trees transplanting machine general structure schematic drawing
Mechanics Model of the Shovel Blade
The shovel blade installed on the supporting frame can move up and down. Because the shovel blades have uniform motion in the start-up process, the internal and external force generated by mutual balance can be calculated using the statics instead of dynamics [3].
Figure 2 shows the following nine forces of shovel blade which influence the resistance of the shovel blade: soil gravity W , the stillness of the soil lateral pressure P0, soil-shovel blade surface friction and adhesion (µ1 · N), shovel on both sides of pure cutting blade resistance N11 and N12, soil role on the knife edge in shovel to reverse force method N 2, soil-shovel blade cutting edge surface friction (µ1 · N2) , shovel goes on soil caused sword to pressure the soil additional method P b , and the soil to shovel blade with reaction force N0
.
Fig. 2 Shovel knife acorns resistance analysis
The mechanics theory is applied for the projection into σ axis. The shovel resistance P of the shovel blade can be obtained using the formula below [4]:
H z P =2{R (k 0⋅sin β⋅ctg δ−β) ∫γ(z ) z (1−) dz H 0
+µ[P b +W ⋅cos δ+P 0sin δ+(N 11z +N 12z ) sin δ
−(N 11z +N 12z ) cos δ−2N 2z ⋅sin δ−2N 2z ⋅cos δ
+2µ⋅N 2cos
+µN 2⋅cos a 0⋅sin ω]+N 2z sin δ−N 2z sin δ−N 2z ⋅cos δ2 (1)
When the shovel blades used are identical, the forces that shovel oil cylinder on the shovel blade body tackle with shovel resistance P are equal.
Some researchers employ Simi-experience method, which is widely adapted in soil - machine system dynamics. The method utilizes the empirical formula [5] based on the similarity theory model to calculate the shovel blade resistance.
0. 75530. 2447P =0. 1307X 1. 1884ρs C (13. 9275+0. 5633×100. 0243β) (2)
where, X —— shovel blade displacement quantity(m ); a 0⋅cos ω}+(N 11z +N 12z ) cos δ+(N 11z +N 12z ) sin δ2
s —— soil bulk density(g/cm2);
C—— soil cohesion(Pa );
B—— shovel blade around angle of half horn(°);
The experiment shows that the thickness of shovel blade will directly affect the result of compressive stress, which greatly influences the shovel resistance. To reduce the value of shovel resistance value the thickness of blade must be reduced. ρ
Finite Element Analysis
The three-dimensional moldle of shovel blade is established using Pro/E and the unit is set as meters Newton seconds (m·N·s); the three-dimensional model built is then imported into ANSYS as geometry models. The unit types are set as solid45 and the material is set as steel of 45#. Tensile strength σb =570~690MPa, elastic modulus E=206GPa, and Poisson's ratio µ=0.3[6]. The shovel blade is divided using discrimination grids and solid45. Through the mechanics analysis of shovel blade, it is assumed that the freedoms of the top and bottom are zero in the directions of X, Y, and Z. The number of the nodes of network division is 5,876.
The oil cylinder pressure of the shovel blade increases gradually during the digging process, so the stress should be within the allowable range as long as the oil cylinder pressure on the shovel blade does not exceed the maximum value when shovel reaches itsfinal position).
The shovel the force F[7] is calculated as follows:
F =DS (3)
where, D is the shovel blade oil cylinder pressure; S is the cylinder section area of shovel blade oil; S = 0.01767hm2. The cylinder force of shovel blade oil is 102833N in the final stage.
Within ANSYS, the stress image is acquired using the boundary conditions and the load as shown in Fig. 3. The maximum stress value obtained is 98.926 MPa, which does not exceed the requirement of the allowable stress of material. Observed from the convective stress, the point of stress concentration appears at the top and bottom of shovel blade edge. Structure in these places is weak, which has to be improved in the future.
Fig. 3 Shovel blade Stress of convective in final status
Concluding Remarks
The stress analysis for the shovel blade of the tree transplanting machine has been conducted. Due to the uniform motion of the shovel blade, only the hydraulic driving force and resistance, which the soil imposes on the shovel blade, are investigated in the research. The shovel blade’s mechanics model for the in-depth soil is built and the three-dimensional model is produced using Pro/E.
According to the results of finite element-stress analysis, the stress distribution of the shove blade of tree transplanting machine is reasonable. The Maximum forces of the shovel blade occurs in the final stage of digging process; and the maximum stress value is 98.926 MPa which satisfies the allowable requirements of materials.
References
[1] Zhengping Gu, Ruizhen Shen: submitted to World forestry research (2005)
[2] Jiangguo Yu, Jinwei Qu: Farm machinery research. 38-41 (2006), p.12
[3] Hua Zhang: Small nursery stock move kind of machinery research (Zhejiang University
Publications, China 2008)
[4] Juxin Qu. The digging machines at home and abroad research situation and development
trendNew study of digging machines for trees (China's forestry science research institute Publications, China 2009)
[5] Wenhua Yang,Hang Chen:4YS-600 style shovel blade of trees transplanting machine element
analysis (Farm machinery research Publications, China 2008)
[6] Daxian Cheng: Mechanical design manual edtied by Chemical industry Publications, Beijing
(2002)
[7] Femando J D,Daniel E V: Fuzzy control activisms pensions (Mechatronics Publications, pp
897-920 2000)
Advanced Design and Manufacture IV
10.4028/www.scientific.net/KEM.486
Trees Transplanting Machine Mechanical Model Establishment and Shovel Blade Finite ElementAnalysis
10.4028/www.scientific.net/KEM.486.234