| Hydraulic excavators,as a typical construction machinery,are widely used in various engineering fields due to their high efficiency and strong adaptability.Due to the bad working environment of excavator,the load borne by the working device is mainly complex cyclic load,leading to the main failure form of the working device is the crack or even fracture caused by fatigue accumulation.The boom,as the core component of the working device,bears a relatively severe load.Therefore,the study on the dynamics and fatigue life of the boom is of great significance for improving the structure of the boom and improving the excavation performance,work efficiency and anti-fatigue ability of the working device of the excavator.In this paper,a 90 t hydraulic excavator is taken as the research object,and the dynamic characteristics and fatigue life of the excavator working device are studied by combining theoretical calculation and simulation analysis.The main research contents are:(1)Based on the force analysis of excavator working device in different mining methods,the calculation method of theoretical mining force and mining resistance under different mining methods is determined,and the calculation expression of working cylinder thrust under compound mining methods is determined,which provides theoretical basis for subsequent simulation analysis.(2)By theoretical calculation of the digging resistance and working cylinder driving data as constraint condition,a rigid body model of the hydraulic excavator in ADAMS and dynamics simulation,and according to the comparison of theoretical calculation value and the simulation analysis and working device and the force states of each hinge point,verify the simulation results accord with the theoretical calculation results.By establishing the rigid-flexible coupling model of the hydraulic excavator and performing dynamic simulation,according to the comparison of the simulation results of the rigid body model and the rigid-flexible coupling model,it is shown that the rigid-flexible coupling simulation results are more realistic.By checking the strength of the boom,it is shown that the boom has room for further optimization.(3)Taking the boom size parameters as the design variables and taking the lightest boom mass and the smallest maximum stress value as the optimization objectives,the boom is multi-objective optimization.Design variables with greater influence were selected through sensitivity analysis in ANSYS Workbench.According to the comparison of different response surface precision,the optimal response surface model is selected,and the multi-objective genetic algorithm is used to optimize the solution.After optimization,the mass of the manipulator is reduced by 5.74% and the maximum stress value is reduced by 8.14%,achieving the purpose of lightweight.(4)The load time history of the optimized boom is extracted,and the S-N curve of the material is corrected according to the actual excavation situation.The FEFAT module in MSC.Fatigue is used to analyze the full life of the boom,and the fatigue weak position of the boom is found according to the fatigue life analysis results of the boom.(5)Focus on the study of the welds at the weak positions of boom fatigue,extract the load time history of the boom welds,and use the SEAMW module of MSC.Fatigue to evaluate the fatigue life of the welds at the dangerous locations.According to the fatigue life analysis results of the weld,the dangerous position of the weld is found,and the solution is proposed.This topic through the theoretical calculation and simulation analysis of the means of the combination of hydraulic excavator working device research,for the design and development of the working device to provide technical reference,reduce the cost of research and development to shorten the development cycle,but also for the study of other mechanical structure bearing cyclic load provides a method guidance. |
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