Mini-bus Frame Performance Analysis And Lightweight Optimization

At present,lightweight technology has become a research hotspot in the automotive field.As the core bearing component of the car,the frame structure affects the load capacity,maneuverability and safety of the whole vehicle.Therefore,when designing the frame structure,it is necessary to ensure that the frame is lightly designed on the basis of meeting various performance requirements.For the mini-bus frame of an enterprise,this paper completes the preliminary design of the frame structure based on the topology optimization method,and optimizes the multi-objective lightweight optimization of the frame structure under the premise of ensuring that the frame meets the design requirements.The main work contents and conclusions are as follows:(1)Firstly,the topology optimization model of the frame is established.According to the actual load condition of the frame,the constraints are added.Then,the topology optimization model with the minimum frame structure flexibility of three conditions and the first three-order of frequency is solved,obtaining corresponding compliance value and frequency value.Finally,the minimum flexibility value and the first three-order frequency values are defined as the multi-objective optimization function by using the compromise programming and the average frequency method,which is performed with the volume fraction as the constraint,obtaining the optimized frame topology cloud and completing the preliminary design of the frame structure.(2)According to the specific frame structure and topology optimization results of the frame,the detailed structure and geometric model of the frame are established.Based on the actual working conditions,the finite element model of frame modal,bending condition,torsion condition,emergency braking condition and urgent turning condition is established,and the performance simulation results that meet the design requirements are obtained.The results show that the frame structure is safe and reliable,and there is a space for optimization.(3)Using the modal synthesis method to obtain the MNF modal neutral file of the frame and establishing a simplified model of the vehicle dynamics in the ADAMS software.The D-level pavement spectrum is used as the external excitation input.The load-time curve of the frame and the front and rear suspensions at the contact position is obtained through simulation,which provides the necessary load spectrum data for the subsequent frame fatigue prediction.(4)The quasi-static stress results of the frame are obtained by the inertia release method.Combined with the stress results,load spectrum and material S-N curve,the fatigue life prediction of the frame is completed by the nominal stress method and the Miner damage rule.The results show that the dangerous point life of the frame meets the design requirements.(5)Firstly,through the parameter study and sensitivity analysis,select 12 parts thickness with large influence as the design variable.Then,120 sets of sample points were collected by Optimal Latin Hypercube design method,and the response values of each performance were obtained by finite element software.The approximate model of mass,modal frequency,stiffness of four working conditions and fatigue mileage is established by response surface method.The model accuracy is verified by the accuracy parameters and the fitness map.Finally,taking the first-order frequency of the frame,the maximum fatigue mileage and the minimum mass as objective,the frame multi-objective lightweight optimization model is established based on the other performance requirements of the frame,which is solved by the NSGA-II.The optimized frame not only meets the design requirements,but also the mass loss ratio of the frame reaches by 6.56%,the fatigue mileage increases by 5.29%,and first-order modal frequency vaiue is increased by 4.3%.In this paper,the detailed design and analysis of the structure and performance of the mini-bus frame are carried out,and the lightweight research is carried out to achieve the expected design purpose.The results of the thesis have certain guiding significance for the development of the mini-bus frame.