Random Vibration Fatigue Analysis Ofelectric Vehicle Battery Case Based On Finiteelement Method

With the increasingly serious environmental pollution and energy shortage,the status of traditional fuel vehicles is gradually replaced by new energy vehicles,especially electric vehicles.As the main energy component of electric vehicles,power batteries provide energy for driving.Battery case is the component that holds power batteries,so its performance will affect the normal use of power batteries and then affect the normal running of electric vehicles.In the course of vehicle driving,the battery case was constantly subjected to random excitation from the road transmitted by the body.Long-term random vibration may lead to structural fatigue damage.The static strength analysis and random vibration fatigue life analysis and calculation of battery case structure using CAE technology to ensure that the strength and fatigue life meet the design requirements are of great significance in the development and design of automotive products.In this paper,the battery case of an electric vehicle was taken as the research object.Firstly,the solid size battery case model was established in UG.The model was imported into the finite element software ANSYS Workbench.The static strength of the battery case of an electric vehicle was analyzed under three typical working conditions: bumpy road,braking and turning.The stress and displacement of the battery case under each working condition were calculated.The results show that the maximum equivalent stress is less than the yield strength of the structural material of the battery case under all working conditions,which indicates that the strength of the battery case meets the requirements under these working conditions.Secondly,the first ten natural frequencies and modes of the battery case were obtained by modal analysis with fixed constraints,and the resonance characteristics of the battery case were analyzed.It was found that the natural frequencies of the battery case avoid the frequency band of random excitation on the road surface.Based on the modal analysis results,the harmonic response of the battery case was analyzed by modal superposition method,and the frequency response of the stress and displacement of the battery case structure under vertical,longitudinal and transverse unit acceleration loads were obtained.Then the harmonic response analysis results were imported into the fatigue analysis software nCode design life.Combining with the fatigue characteristic curve of battery case materials,the vertical,vertical and lateral acceleration power densityspectra corresponding to the standard lithium-ion battery pack and system test rules were applied to analyze the random vibration fatigue life of battery case model,and determine the structure of battery case in three directions.The results show that the fatigue life of the battery case doesn’t meet the design and service life requirements of general electric vehicles.The random vibration fatigue life of the battery case can be quickly estimated by the vibration fatigue analysis based on the frequency response results,which provides a basis for the optimization and improvement of the product.Finally,four different types of acceleration load spectra and four different values of damping were applied to the battery case model to analyze their effects on random vibration fatigue results.The results show that the main influence of random excitation on the fatigue life of the structure is in the low frequency band.The minimum fatigue life of the battery case structure increased nonlinearly with the increase of the damping coefficient.These conclusions provide some theoretical references for the vibration fatigue design of battery case and help to shorten the product development cycle and accelerate the design process.