Vehicle Body Fatigue Analysis Method Study Base On Vibration Fatigue

Now in the car design phase, the computer aided engineering (CAE) has become animportant part in the research and development of new automobile, under the condition ofno prototype for designer to provide relevant parameters of automobile structureperformance, to guide the optimization of the new structure, etc。Based on the finite element method, the elastic-plastic mechanics and the dynamicsanalysis method has been widely used in the automobile industry，main applications in eachsubstructure of automobile in strength, safety, durability and NVH analysis and other fields.Due to the fatigue failure is one of the main failure mode of the engineering machinerystructure, so fatigue life analysis of the design phase for guiding the design of automobilestructure prevent fatigue failure caused by improper design has important significance.This paper, taking a designing domestic light bus as the research object, the followingwork:(1)Introduces the commonly used frequency domain fatigue analysis of related theoryand the basic flow. Taking a designing light bus model of vehicle research and developmentcompany as an example, use the Altair company’s professional software Hypermeshestablishe the model of finite element model.(2) Use the MSC company’s MSC. NASTRAN modal analysis for finite elementmodel of the body, to check the model, and analysis of car body structure dynamics byobserve the low order natural frequency and vibration mode.(3)Establishing finite element model of the front and rear suspension and assemblefull body model with body model, take wheel center as the excitation point calculatefrequency response, stress response results as input vibration fatigue analysis.(4) Using multibody dynamics software MSC. ADAMS/car to build the coupled modelof the vehicle, grade B road spectrum as the input for the vehicle driving straight simulation,and extract loading process of the wheel center, using load processing modules of MSC.Fatigue conver the loading process into PSD. Make results of frequency response and PSD of loading process import vibration fatigue of MSC. Fatigue calculate fatigue damage, andcompared with fatigue crack position of prototype car after road test.(5) Introduce DOE, the approximate model and genetic algorithm in optimization ofrelated theory，through MDO software Isight integrated MSC. Nastran and MSC. Fatigue,multidisciplinary optimization of light bus’ drive axle shell consideration stiffness, modaland fatigue, achieve the purpose of lightweight design.