Lightweight Optimization Design Of Commercial Vehicle Frame Based On Performance Driven

At present,the fuel consumption of 100 kilometers of commercial vehicles in China is generally high.With the increasingly strict requirements of fuel consumption laws and regulations,it is significant to apply advanced technology on commercial vehicles.As a key energy saving technology,lightweight technology is of great significance for heavy-duty commercial vehicles to achieve energy saving and emission reduction and to meet the fuel consumption regulations.The weight of the commercial vehicle frame accounts for about 10% of the total weight of the commercial vehicle,so the lightweight design of the commercial vehicle frame is meaningful to commercial vehicles.In this paper,a performance-driven optimization design of heavy-duty tractor frame was carried out.Under the premise of ensuring the strength,stiffness,main modal performance and fatigue life of the tractor frame,the optimization design of the frame of a heavy-duty tractor was carried out.The main contents and results of the research are as follows:Firstly,through the procedure of geometry cleanup,meshing,materials and properties assigning,connections of beams of the frame using rivets and bolts,the FEA model of the frame was established.Secondly,the static and dynamic performance of the frame was analyzed and evaluated.The static strength analysis of the frame under four typical working conditions was carried out to obtain the stress distribution and displacement change of the frame under each typical working conditions,which were used as the static performance evaluation index of the frame.The strength and stiffness of the frame were evaluated to determine that the static performance of the frame met the design requirements.The main low-order modal frequencies and vibration shapes of the frame were obtained by computational modal analysis,which were used as dynamic performance evaluation indexes of the frame.The simulation result was compared with the modal test result to verify the accuracy of the FEA model of the frame.Thirdly,the multi-body dynamics modeling and simulation of tractor were carried out.Based on each subsystem multi-body model previously offered by the research group,the flexible body model of the frame and other subsystem models of the tractor were assembled through the communicator to obtain the rigid-elastic coupling virtual prototype model of the whole tractor.Based on the harmonic superposition method,the three-dimensional B-level road surface was established,and the multi-body dynamics simulation of the tractor was carried out.The load-time history curves of each connection point on the frame were obtained.Fourthly,inertia release method was used to obtain the stress response of the frame when unit load was applied at each connection point of the frame.The S-N curve of the frame material was simulated according to its performance parameters.The load-time history curves of the connection point on the frame were corresponded to the stress response,combined with S-N curve established before,fatigue life of the frame as well as the danger point were determined based on nominal stress method.Finally,the lightweight optimization design of the frame was carried out.Multi-objective optimization model of the frame was established: 3 shape variables and 15 thickness variables were selected as design variables,with the biggest displacement of bending condition,the biggest displacement of torsion condition,the maximum stress of torsion condition and first mode frequency of the frame selected as constraints,and the maximal of fatigue life and the minimum of the mass of the frame selected as the optimization goal.180 groups of sample points were selected for design of experiment.Based on the result of the design of experiment,the approximate models of each constraint response and optimization target were established and verified.The lightweight design of the frame was carried out and the Pareto front of the optimization target was obtained.From the Pareto front,the solution that meets the optimization design requirements and have the least mass is selected as the optimal solution of the multi-objective optimization of the frame in this paper.The performance of the optimized frame was verified.Under the premise that the performance of the frame meets the design requirements,the weight of the frame is reduced by 155 kg,and the weight loss rate reaches 17.2%.The effect of the lightweight design is significant.The results of this paper have certain engineering application value for the lightweight optimization design of tractor frame.