Study On Fatigue Durability For A SUV Body In White And Structure Improvement

Fatigue durability of vehicle refers to the capacity of vehicle that does not appear to lead to failure of the function in the expected mileage.It is related to the safety and reliability of vehicle,as one of the most important indicators to evaluate the performance of vehicle,has important impacts on both of the vehicle‘s quality and credibility.Traditionally,the problem of fatigue and durability has been solved by a test method,which is costly and has a long development cycle and can't be adjusted in time according to the design changes.At present,the combination of fatigue durability test technology and CAE to guide the design,verification and optimization of automotive products has turned into a hot research of the major vehicle enterprises.In this paper,the following research was carried out in the background of a certain type SUV cracking problem in the process of fatigue durability test.The main content includes:(1)Building the finite element model of the body-in-white based on 3D digital model of the SUV.Based on the model,free modal analysis was carried out,and the natural frequency and vibration mode of the body structure were analyzed.(2)The multi-body dynamics model of rigid-flexible coupling was established,which includes subsystems such as front and rear suspension,steering and stabilizer bars.Based on the rigid-flexible coupling model,the load information between the body and frame was extracted under the classical working conditions.Then static strength of the body in white was simulated using method of inertia relief,and the effectiveness of the simulation was verified by the strength test.(3)The dynamic load spectrum of the vehicle body installation points was extracted by combining the six-component load spectrum and the rigid-flexible coupling model.The fatigue analysis method based on Miner's linear accumulative damage rule and strain-life theory is adopted.Welding and sheet metal fatigue life were predicted,and accordingly trace the cause of cracking,provide a reference for the actual fatigue durability test.(4)Combined with the simulation results,three structural improvement schemes were presented and the fatigue simulation analysis was carried out to select the best solution of cracking.The fatigue durability road test was carried out to verify the effectiveness of the optimization scheme and the feasibility of the vehicle fatigue durability research method.