| In recent years,with the continuous advancement of national infrastructure construction,large hydraulic excavators have been widely used in various projects.The development of hydraulic excavators in China is relatively late,especially in the technology research and development of large hydraulic excavators,which has been constrained by others for a long time.In order to speed up the breakthrough of technological blockade,China has proposed "Made in China 2025" and vigorously developed its manufacturing industry.As the key structural part of the excavator,the working device of the large hydraulic excavator directly affects the efficiency and service life of the engineering construction.In this thesis,the finite element method is used to simulate the structural force of each part of the excavator working device through ANSYS Workbench software,and the stress and deformation of excavator boom,bucket rod and bucket under different working conditions are compared and analyzed;At the same time,Based on typical working conditions,an optimized model was established for the boom,stick and bucket,and the lightweight design was carried out.Finally,the performance of the optimized new structure is evaluated.The results show that:According to the three typical working conditions(bucket excavation,bucket rod excavation and compound excavation)during the operation of the excavator,the theoretical digging force of the bucket rod and bucket and the force of each hinge point of the working device are obtained through moment balance calculation condition;Based on the force analysis,the parameterized three-dimensional finite element analysis model of boom,bucket rod and bucket is established,and the structural statics calculation is carried out respectively.The results show that: in three typical working conditions,the structural strength of the three meet the design requirements,the maximum stress of boom and bucket rod is concentrated at the junction of the upper wing plate and the left and right web,and the maximum displacement is at the front end of the boom and bucket rod.The maximum stress of the bucket is concentrated in the bucket teeth and blade plate,and the maximum displacement is in the middle teeth.By comparing three typical working conditions,the dangerous working condition was screened out as compound excavation working condition..Based on this,the optimization models of the three were respectively constructed,and the size of 18 design variables including the boom,bucket rod and bucket were optimized through response surface optimization.Rebuild the 3D finite element model for the optimized structure and perform performance evaluation,including structural strength evaluation,modal analysis,transient dynamic analysis based on impact conditions and time step load based on the selected compound excavation conditions fatigue analysis.The structural strength analysis shows that the purpose of effective weight reduction is achieved while ensuring that the structure meets the strength requirements.the total mass of the boom was reduced by 696.8 kg,and the weight was reduced by 10.1%.The mass is reduced by 259.2 kg,and the weight is reduced by 8.8%;the total mass of the bucket is reduced by 217.4 kg,and the weight is reduced by 9.0%.The modal analysis of the boom and bucket rod based on the impact conditions shows that the first and second order vibration shapes of the boom and bucket rod are similar,the first order is the left and right swing of the front end,and the second order is the up and down swing;The last four-order deformation is relatively large,mainly concentrated in the web and ear plate.The transient dynamic analysis of the boom and bucket rod shows that the bucket rod cylinder support of the boom and the ear plate of the bucket rod are relatively weak compared to other parts.The fatigue analysis of the boom and bucket rod shows that the vulnerable position of the boom is located at the lower wing,and the vulnerable part of the bucket rod is located at the hinged position of the boom.The thesis has 50 pictures,18 tables,and 82 references. |
