Connection Analysis Of Battery Box Of Pure Electric Vehicle Under Random Vibration Conditions

As the global energy problem becomes more and more serious,electric vehicles as a means of transportation have come into the sight of the public.When the number of electric vehicles is increasing,more and more product problems are exposed.The battery box is a protective barrier for the power battery pack.Therefore,studying the connection reliability of the battery pack is of great significance to the development of pure electric vehicles.Based on the power battery box of a certain pure electric vehicle,this thesis analyzes the reliability of its lithium battery power battery pack from the perspective of connection,and designs the battery box to be lightweight on the premise of meeting the performance requirements.First,the overall structure of the power battery pack is evaluated.Based on the geometric model,the finite element model is meshed,connected,and given material properties.The bolt connection is modeled by umbrella beam elements,and the spot weld element is ACM2.Then perform modal and random vibration analysis on the power battery box.The modal analysis results of the battery box show that the first-order natural frequency of the battery box is 30.08 Hz,which meets the low-order modal natural frequency requirements of electric vehicles without resonance.Random vibration analysis results show that the structure of the battery box meets the stress in the X,Y,and Z directions and meets the design requirements.Secondly,using the root mean square value of the axial stress power spectrum density of the screw and the bolt strain energy value as the evaluation parameters of the bolt vibration loosening of the battery pack,based on the random vibration analysis results,the bolt loosening and loosening performance is evaluated,and the bolt with higher risk is obtained,and optimize the bolt spacing.After optimization,the Z-direction screw axial stress power spectral density root mean square value is reduced by 38%.the bolt strain energy value is reduced by 46%.the risk of bolt connection vibration loosening is reduced,and the battery box is improved.The connection reliability verifies the feasibility of the optimized scheme.Finally,based on the frequency analysis method,the random vibration analysis results are used as inputting,combined with the SN curve and the acceleration power spectral density value,and the n Code software is used to perform weld spot fatigue life and damage prediction analysis on the battery box.The results show that the weld spot fatigue life meets the test standard requirement.Taking the thickness of each component of the battery box as a design variable,modal and dynamic performance as constraints,and quality as an optimization goal,a lightweight model was established.The weight of the battery pack box of the optimized scheme is reduced by 2.9% compared with the original scheme,and the fatigue life of the weld spot of the optimized scheme meets the requirements of the test standard.