Lightweight Optimization Design Of Heavy Duty Commercial Vehicle Cab

At present,although the number of commercial vehicles is smaller than that of passenger cars,the fuel consumption per 100 kilometers of commercial vehicles is relatively high,and the annual mileage is long,therefore the total fuel consumption is high.With the increasingly stringent fuel consumption regulations,the use of advanced commercial vehicle energy-saving technology is particularly important and urgent.As a key energy-saving technology,lightweight technology is of great significance for energy saving and emission reduction of heavy commercial vehicles.The commercial vehicle cab,which accounts for about 10% of the total vehicle mass,has far less lightweight risks and costs than other components.Therefore,the lightweight of the cab is significant to the weight reduction of the entire vehicle.Based on the industry-university-research cooperation project “Optimization Design of Commercial Vehicle Cab Structure Based on Passive Safety”,the lightweight optimization design was carried out for a heavy commercial vehicle cab on this paper as the following steps:Firstly,the finite element model of the cab was established through the procedure of geometry cleanup,meshing,materials and properties assigning,and connections of different parts using spotweld and bolt.Secondly,finite element analysis and evaluations for the cab under different conditions were adopted.Modal and stiffness analysis were carried out,followed by the obtaining of first order torsional natural frequency,bending stiffness and torsional stiffness;the finite element models of frame,suspension,interior and dummy were established and assembled to the cab model to build the finite element model of the cab for passive safety analysis.The accuracy of the model was validated through experiments under ECE R29-02,and passive safety analysis of the front impact,front pillar impact and roof strength was performed under ECE R29-03,after which the parameters best representing the survival space under different conditions were used as evaluation indexes of passive safety.Thirdly,the relative sensitivity analysis for bending stiffness,torsional stiffness and the first order torsional natural frequency was adopted.The structural contribution analysis was further carried out for the passive safety index of the cab.18 thickness variables and 4 material variables were selected as design variables for multi-objective optimization according to the results of sensitivity and contribution analysis.Finally,multi-objective lightweight optimization were carried out for the cab.Before the optimization,the structural improvement of A-pillar was performed according to the results of safety analysis and contribution analysis,for the reason that the analysis of front pillar impact did not meet the requirements.On the basis of structural improvement,design of experiment was carried out followed by the establish of approximation model.The accuracy of the approximation model was validated and multi-objective lightweight optimization based on the approximation model was performed.The Pareto frontier was obtained,from which a solution satisfying the passive safety requirement and making the mass of cab as small as possible was selected from the Pareto frontier as the optimal solution for the optimization.The optimized cab has a mass reduction of 29.35 kg and a weight loss rate of 7.67%,under the premise of satisfying various performance requirements,which has a significant lightweight effects and engineering application value for the structural design for commercial vehicles.