Vibration Analysis And Structure Optimization On Tree-digging Machete

The mechanization of tree transplanting in China has been slow to develop,and the introduced tree-digging machines can not effectively meet domestic demand.Traditionally relying on manpower to use shovel shovel operation,high cost and low efficiency.In recent years,the vibrating machete tree digging machine has become one of our main tree transplanting machines,using vibration characteristics to reduce digging resistance.However,there is little research on the vibration of the machete during the excavation process.Excessive vibration will easily cause the soil ball to break.Therefore,it is of practical significance to carry out vibration test and modal test analysis of tree-digging machete.In this paper,the vibration machete tree digging machine is firstly analyzed the excitation frequency and vibration amplitude through the vibration test of the tree machete under multiple working conditions;Finite element modal simulation analysis;then through experimental modal analysis,the finite element modal simulation results are verified,and the natural frequency of the tree-cutting machete is analyzed;followed by orthogonal test and static stress analysis The structural parameters are optimized.Finally,the tree-cutting machete before and after optimization is studied by discrete element simulation and compared with their vibration-reducing characteristics.The main research contents and results are as follows:(1)Vibration test of the machete under different working conditionsThe data from each measuring point was analyzed in frequency domain under 6working conditions such as no load and full load.The results show that the working condition is that when the tree-digger is idling only at the engine idling speed,the maximum vibration amplitude at 45 Hz is 2.54 m/s~2;when the tree-digger is idling only at the engine's large throttle condition,the amplitude is 90 Hz The maximum is0.56 m/s~2;under the full throttle of digging trees,the maximum amplitude caused by the vibration frequency at 40 Hz is 36.91 m/s~2.Through analysis,it is found that the exciter vibration frequency of the tree-digging machete is larger at 40.00~70.50 Hz,and its maximum amplitude is 36.91 m/s~2 under full-load tree-digging throttle.(2)Modeling and Modal Analysis of Scimitar DiggingWith the Handyscan-3D scanner to scan the tree-cutting machete,use Solidworks software to process the scan results of the tree-cutting machete and build the model,and then use the finite element simulation software ANSYS to perform finite element modal analysis on the model and simulate the calculation 6th order natural frequency and vibration mode before digging the tree machete.Use the modal test and test system to test the modal test of the tree-cutting machete.Comparing the results of finite element simulation calculations with the results of experimental modal tests,it is found that the maximum error of the natural frequency in the results is 6.8%,which further verifies that the finite element is reliable for the modal analysis of tree digging.It was found that the first-order natural frequency of the tree-cutting machete is 66.55 Hz,which coincides with the excitation frequency of the tree-cutting machete from 40.00 to 70.50 Hz,which will cause the tree-cutting machete resonance.(3)Research on Optimization of Structure Parameters of Digging ScimitarBased on the existing structural parameters of the tree-cutting machete,the three factors of the narrow-end knife width,narrow-end knife thickness,and wide-end knife thickness of the machete are selected,and the first-order natural frequency and the first-order maximum deformation variable are used as evaluation indicators.Perform orthogonal test design.Using the previous finite element model simulation analysis,it is found that the narrow end knife thickness is a parameter that has a significant effect on various indicators,the narrow end knife width is second,and the wide end knife thickness is less affected.To increase the first-order natural frequency to avoid coincidence with the excitation frequency,and to reduce the first-order maximum deformation,the narrow-end blade thickness can be appropriately increased,and the narrow-end blade width can be appropriately reduced.The optimal structural parameters of the machete for digging trees were calculated:the width at the narrow end was 12.18 cm,the thickness at the narrow end was 8 mm,and the thickness at the wide end was 28 mm.The optimized tree-digging machete structure model was subjected to finite element modal analysis,and the first-order natural frequency was 76.65 Hz,the first-order maximum deformation was 24.70 mm,and the optimized mode and optimization.The static stress analysis was basically the same before.The static stress analysis found that the maximum stress of the optimized tree-digging machete was5.93 Mpa,which was far less than the yield strength of the material.Therefore,it was inferred that the optimized tree-cutting machete could meet the requirements of working strength.(4)Research on Drag Reduction Characteristics of Digging ScimitarBy analyzing the structure and mechanical characteristics of soil particles,the Hertz-Mindlin with Bonding contact model was selected to perform discrete element simulation on the process of digging the tree before and after the optimization of the excavator,and the simulation analysis in the EDEM discrete element system.The difference between the resistance of a tree-cutting machete under vibration and non-vibration.Among them,the optimized resistance of the tree-cutting machete during non-vibration operation is 894 N,which is about 30%less than before optimization,and the resistance during vibration operation is 418N,which is about 6%less than before optimization.