| The subframe is a key component of the sweeper,which is mainly used to carry the sub-engine and its related accessories.Therefore,the lightweight design and optimization of the subframe of the sweeper have important engineering practical and theoretical significance for the energy saving,emission reduction and performance improvement of the vehicle.In this thesis,the subframe of the sweeper is taken as the research object.Through the static analysis of the subframe,the mass redundancy of the subframe structure is found to be serious.In view of the problems existing in the existing structure,the lightweight design of the original subframe is carried out by means of material replacement.The multi-objective topology optimization method is used to obtain the subframe topology structure under the static multi-working condition and the dynamic working condition.With the results of topology optimization as a reference,the secondary lightweight design of the steel and aluminum subframe is carried out by machining weight reduction holes.Taking the secondary lightweight design subframe as the object,the BP neural network and polynomial function model are used to construct the function model of the component thickness,fatigue life and quality of the subframe.By using the multi-objective genetic algorithm to optimize the parameters,the final lightweight design scheme of the subframe is obtained.The optimized subframe structure achieves the lightweight effect of reducing weight by 37.42% on the premise that all indexes meet the safety requirements.The main research contents are as follows:(1)The finite element model of the subframe of the sweeper is established and the static analysis is carried out.Then,the stress and strain of the right side rail of the subframe are analyzed and checked by analytical method.The results of analytical verification and finite element analysis are compared and analyzed.The strength and stiffness of the subframe are qualified,and there is a lot of weight reduction space.(2)The steel and aluminum replacement scheme of the subframe structure is determined by orthogonal test.The lightweight design scheme of the steel aluminum bolt connection of the subframe is determined,and the structure of the corresponding rail assembly is modified;Then,considering the static multi-working conditions and the dynamic frequency characteristics of the structure,the multi-objective topology optimization design method is adopted to obtain the multi-objective topology optimization structure of the steel-aluminum subframe.With the results of topology optimization as a reference,the secondary lightweight design of the steel-aluminum subframe is carried out by machining the weight reduction holes.(3)In order to verify the accuracy of the bolted finite element model of steel and aluminum dissimilar materials established by rigid element method in the fatigue life analysis process of subframe structure,a comparative verification between the test and simulation analysis of steel and aluminum dissimilar materials is designed.The accuracy and feasibility of the scheme are verified by comparing the experimental results with the simulation results.Finally,the fatigue life of the steel-aluminum subframe after secondary lightweight design is analyzed by using nominal stress method.(4)Using Latin hypercube sampling method,the thickness of the steel-aluminum subframe after secondary lightweight design is taken as the variable for experimental design.BP neural network and polynomial function model are used to construct the function models of plate thickness,fatigue life and overall mass respectively.Using the function model,multi-objective genetic algorithm is used to find the optimal solution.The optimized subframe achieves a good lightweight effect on the premise that all indicators meet the requirements. |
