Research On The Performance Deterioration Rules Of Foam Silicone Rubber For Static Sealing Of Lithium Battery Cases

Taking the lithium battery case static sealing system as the research object,the foamed silicone rubber sealing strip was studied through the combination of theoretical simulation and experiment.Main research contents: Carry out the degradation test of material-grade rubber samples and obtain the rubber degradation law at different time nodes;establish the mechanical performance simulation model of the sealing system through finite element simulation;The leakage rate of the sealing system under certain working conditions was obtained through the porous media model and micro contact model.The subject static seal is a foamed silicone rubber material,which is made of a silicone rubber matrix through a foaming process.In order to investigate the changes in mechanical properties and sealing performance of foamed silicone rubber under harsh environments,a 50-day long-cycle accelerated hot air aging test,a temperature and humidity accelerated aging test,and a salt spray deterioration test was carried out.Hot air accelerated deterioration tests were carried out at 120 ? and 140 ?.Temperature and humidity accelerated aging carried out the test of four working conditions of 80% 85 ° C,85% 85 ° C,90% 85 ° C,and 95% 85 ° C.Deterioration of salt spray has been carried out under the conditions of ambient temperature of 40 ? and salt spray pressure of 0.2MPa.At different aging time points,the compressive permanent deformation rate,stress-strain curve and other aging properties and mechanical properties of the samples are measured.The aging rules of foamed silicone rubber during aging were analyzed.At the same time,the stress-strain curve data provides data input for finite element numerical simulation and leakage rate calculation.Using ANSYS finite element simulation software to model the foamed silicone rubber seal.The Von-Mises stress of the foamed silicone rubber seal under different compression amounts and the contact pressure of the contact area between the seal and the shell were analyzed.The stress and strain data were collected through a universal testing machine,and the lateral strain data during the compression process of the foamed silicone rubber was obtained using a camera and image processing software.The Ogden 3rd(Form)model defines the material properties of foamed silicone rubber.It solved the problem that the finite element calculation of the foamed material with large compression volume and variable volume was difficult to converge.The finite element simulation results were verified by pressure-sensitive paper.Von-Mises stress and contact pressure variation were obtained by simulating samples with different aging times.Based on the micro-contact model and the porous medium model,a set of calculation methods for the analysis of the interface leak rate of the foamed silicone rubber static seal system was established.The morphological characteristics of the surface of the foamed silicone rubber were obtained by means of white light interferometer and mathematical fitting,and the key parameters of microscopic surface characterization were obtained.Through the coupling of macro-contact pressure and micro-rough peak contact pressure,the classical Greenwood-Williamson micro-contact model is used to solve the boundary conditions of the porous media model.Aiming at the unique state of the cells and the rubber matrix on the surface of the foamed material,a porous medium model was used to describe the fluid flow state at the sealing interface.The pressure field distribution of the contact surface of the foamed silicone rubber and the leakage rate of the fluid medium were obtained.In this paper,the leakage rate of the sealing end face under different medium pressures and different compression amounts was calculated by using a leaking silicone rubber leak model.The effects of micro-elastic modulus,contact pressure macro-parameters,roughness and rough peak radius on the leakage rate were analyzed.Based on the aging test data,the change law of the leakage rate of the foamed rubber sealing strip under different aging time was analyzed.