Research On Multi-Objective Optimization Design Of Electric Wheel Dump Truck Frame Based On Interval Method

The electric wheel dump truck is the main transport equipment in the open pit,with a capacity of hundreds of tons and a working time of nearly20 hours a day,and the mine road is undulating and uneven,resulting in a very harsh working environment.And the frame as the main load-bearing parts,the mechanical properties and fatigue life of its structure directly determine whether the vehicle can run safely.However,in the traditional empirical frame design process,the mechanical properties of its material parameters are often taken as fixed values,without considering the influence of random uncertainties in the actual manufacturing process of the frame.Therefore,this paper combines the interval methods such as blind number theory and interval number to study the structural performance of the frame,conducted fuzzy multi-objective topology optimization and fatigue life evaluation of the vehicle frame,and performed fatigue-resistant lightweight design research on it.The main research of this paper is as follows.1.In this paper,the allowable interval strength,allowable interval bending stiffness and allowable interval torsional stiffness of the frame material are derived based on the blind number theory,experimental data of the frame parent material and finite element simulation analysis after taking into account the uncertainties in the material and the structure.Then,Latin hypercube sampling was used to evaluate the interval dynamic stress,bending stiffness and torsional stiffness of the frame under the limit conditions such as horizontal bending condition,emergency braking0 condition and torsional condition,and the evaluation results showed that the interval strength of the frame under emergency braking condition interfered with the dynamic stress interval,and the bending stiffness and torsional stiffness needed to be improved.2.To solve the problem of insufficient frame stiffness.Firstly,a single objective topology optimization function is established for different working conditions of the frame.Secondly,based on the fuzzy variable weight method to dynamically assign each single objective weight coefficient,fatigue stress constraint is established under the consideration of frame life.The fuzzy multi-objective topology optimization of the frame structure is conducted by Opti Struct solver,and a new frame structure satisfying the frame stiffness and dynamic frequency requirement is obtained,and finally the topology structure is reconstructed to provide the basis for interval multi-objective optimization of the new frame.3.In this paper,based on a small amount of sample data and interval method,an interval strain energy density fatigue life prediction model is proposed.First,a small amount of strain energy fatigue life data was rearranged and combined based on the interval method to expand the data fitting sequence,and the interval strain energy density-fatigue life curve was constructed.Secondly,on the basis that the validity of the finite element model of the electric wheel dump truck frame is guaranteed,the nonlinear finite element analysis of the frame under equivalent load is conducted,and then the total strain energy density at the danger point is calculated based on the stress-strain response,and the interval life of the frame is predicted based on the interval strain energy density method.Finally,the fatigue life and weight of the frame are used as the optimization objectives,and an interval multi-objective optimization mathematical model with different frame base material plate thickness is established.Based on the accuracy of the approximate model,a Pareto-optimal solution is obtained by global search based on the non-dominated sorting multiobjective genetic algorithm.The optimization results show that the lower limit of the fatigue life of the optimized frame structure is improved by61.2%,while the weight of the frame is reduced by 13.2% compared with that before optimization and by 5.7% compared with that of the original frame before topology optimization.In summary,this paper conducts a detailed and systematic study of the frame structure performance and optimal design based on the interval method,which provides a new reference idea for the future design of electric wheel dump truck frame structure.