Finite Element Analysis And Structural Optimization Of Hydrogen Fuel Cell Bus Frame

Under the dual pressure of exhaustion of oil resources and environmental pollution,new energy vehicles have become the focus of attention.As an important part of the development of new energy vehicles,the development of hydrogen fuel cell vehicles usually goes through four steps:conceptual design,detailed design,FEM simulative analysis,experimental verification.And FEM simulative analysis can not only reduce tedious experimental verification,and it also can save R&D costs.Therefore,it is of great significance to improve and optimize the frame structure based on the finite element analysis results for the development of new energy vehicles.Based on the two-dimensional drawings of the frame,a three-dimensional model of the hydrogen fuel cell bus frame was established by using SolidWorks.Then,the model was simplified in SCDM.Finally,the FE Model of the hydrogen fuel cell bus frame was established by using HyperWorks.In order to verify the strength and rigidity of the frame,the static strength analysis of the frame under nine typical operating modes was carried out.We can see that the frame of the hydrogen fuel cell bus is prone to accidents when torsion occurs from the results of the analysis,and the maximum stress is 257MPa,so the safety factor of the frame is insufficient,and the maximum distortion is 10.7mm,so the torsional rigidity of the bus frame is insufficient.In order to study the vibration performance of the frame,the modal analysis under free boundary condition of the bus frame was carried out,and the first ten modes of the bus frame model were extracted.The results show that the eighth natural frequency is 31.2Hz,which is close to the drive shaft pumping frequency(30Hz),and the bus frame is prone to resonance.In order to obtain the relationship curve between the dynamic response and the vibration frequency in the high stress region of the frame,the frame was analyzed by the modal superposition method,and the results of the frequency response analysis and the modal analysis are verified each other.In order to study the fatigue reliability of the frame,the five block diagram of the fatigue analysis of the frame was established by nCode DesignLife based on the results of the static strength analysis of the frame,and the load spectrum and material fatigue characteristic parameters were defined.The fatigue dependability of the bus frame under multiple operating modes was analyzed,and the position of insufficient fatigue life was found in advance.According to the results of the finite element analysis and the fatigue dependability analysis of the frame,the variable density topology optimization theory was adopted to study the multi-stiffness topology optimization of the frame structure under multiple operating modes,and the minimum strain energy of the hydrogen fuel cell bus frame was taken as the objective function,and the volume ratio of the hydrogen fuel cell bus frame was taken as the boundary condition.The original frame was further modified,and the sizing design of the bus frame was further carried out based on the result of the topology optimization.We can see that the maximum stress of the optimized bus frame in the torsional operating mode is 169MPa from the results of the static strength analysis,and the safety factor is 2.04,and the maximum distortion is 6.37 mm,which means the rigidity and the strength of the hydrogen fuel cell bus frame were enhanced,and the rigidity and the strength both meet the safety requirements;the main external pumping frequency can be avoided by the natural frequency of the frame,so that the occurrence of resonance phenomena can be avoided;the peak value of dynamic response of the frame frequency response analysis decreases as a whole,especially when the frequency is between 68Hz and 71Hz,it is close to the nineteenth natural frequency of the frame,and the distortion response curve of the bus frame almost loses the resonance peak,and the anti-vibration performance of the frame was enhanced;the minimum fatigue life cycle is5.034×10~5 times which satisfies the safety fatigue life standard.