Design And Optimization Of Working Device Of Mechanical Excavator

Mechanical excavator is widely used in open-pit mining because of its strong stripping force,high working rate and flexible construction.With the development of China's economy,the demand for ore in China is growing rapidly.In the face of the requirements of high efficiency and low cost of mining,mechanical excavators need to be updated and researched constantly.This thesis takes the working device of FWK-4a mechanical excavators of Fukuang group as the research object.The working device was designed and optimized,and the bucket capacity was increased from 4.6m3 to 5.6m3.The main contents of this thesis are as follows:(1)Firstly,the digging resistance of the mechanical excavator in the process of digging is analyzed and calculated,and the four working conditions of the mechanical excavator and the parameters of the working device of the 5.6m3 mechanical excavator are determined.Then calculate the lifting force and pushing pressure required under four working conditions,and then get the power of lifting and pushing motor.Finally,in order to facilitate the design,a 5.6m3 mechanical excavator calculation system is compiled.(2)According to the original structure,a three-dimensional model of 5.6m3 mechanical excavator working device is established.The static analysis of bucket,stick and boom under four working conditions is carried out by using ANSYS software,and the dangerous position of high stress is determined.Based on the static analysis,it is concluded that the original structure of the working device can not meet the working requirements of 5.6m3 mechanical excavator and needs to be improved.(3)Optimize the structure of the bucket and the stick of the working device.After using workbench to model the bucket parametrically,the relationship between the position of the lifting eye and the maximum stress and total deformation of the bucket is analyzed,and the optimal position of the lifting eye is determined.At the same time,the structure of the parts in the dangerous position of the bucket is improved,and the bucket is remodeled and statically analyzed.The bending moment of the stick is analyzed,the stick is redesigned according to the equal strength principle,the three-dimensional model of the stick is established and the static analysis is carried out.The safety factor of the optimized bucket is 1.54,and the stick is 2.05,which meets the requirements.(4)Aiming at the lightweight design of the boom,an optimization method combining agent model and differential evolution algorithm is proposed.Firstly,the training points and test points are obtained by the Latin hypercube design method.The polynomial response surface model,radial basis function model,Kriging model and Shepard model are established.According to the evaluation criteria,the model types of boom mass,maximum stress and total deformation are determined.Then,differential evolution algorithm is used to determine the design parameters that meet the maximum stress and total deformation constraints and the minimum boom mass.In addition,the topology of the optimized boom is optimized.After differential evolution algorithm optimization and topology optimization,the total mass of the boom is reduced by 12.8%,and the strength and stiffness meet the design requirements.(5)The modal analysis of the stick and boom is carried out respectively.The results show that the stick and boom will not resonate with the crowd motor and lift motor in the working device.In order to prevent overturning,stability analysis is carried out because the quality of mechanical excavator has changed after optimization.