Study On Viscoelastic Poisson's Ratio Test And Mesoscopic Prediction Method Of Solid Propellant

The viscoelastic Poisson's ratio of solid propellant is an important input parameter for the structural integrity calculation of solid motor.Small changes in the thousandth position will seriously affect the results of motor structural integrity analysis and storage life estimation.The viscoelastic Poisson's ratio of the propellant is related to time,temperature,strain rate and other factors.How to accurately measure and accurately predict the propellant Poisson's ratio has always been a difficult problem in the industry.In this paper,a propulsion Poisson's ratio measurement test based on digital image correlation(DIC)method is carried out.A stepwise equivalent representative volume element(RVE)model reflecting the mesostructure of the propellant was established.A mesoscopic finite element predictive model of propellant without defects and considering ?dehumidification' damage was constructed.The prediction of the macroscopic mechanical properties of the propellant on a mesoscale scale is achieved.The main research contents are as followsBased on the DIC method,the viscoelastic Poisson's ratio of the propellant under pseudo-real conditions was measured,and the time-temperature-strain rate equivalent relationship of the viscoelastic Poisson's ratio was established.The force characteristics of propellant for solid motor under the typical conditions of vulcanization cooling and ignition pressurization.Based on the DIC method,a test scheme for measuring the propellant Poisson's ratio using a stress relaxation test and a uniaxial constant tensile rate test was designed.The variation of the viscoelastic Poisson's ratio of the propellant with time,temperature,initial strain and loading rate was studied.The time-temperature-strain rate equivalent relationship of the propellant Poisson's ratio was established.Based on the step-by-step equivalent propellant RVE model generation strategy,a mesoscopic finite element model for propellant mechanical properties prediction was constructed.According to the group distribution bit points of propellant,a step-by-step equivalent meso-mechanical performance meso-predictive method is proposed.Based on the improved stochastic placement algorithm,the propellant RVE model is generated by the step-by-step equivalent strategy.By constructing a two-dimensional mesoscopic finite element predictive model of propellant,combined with the homogenization method,the viscoelastic Poisson's ratio of the propellant under different load conditions is predicted,and the prediction of the macroscopic mechanical properties of the propellant on a mesoscale scale is achieved.Based on the Park-Paulino-Roesler(PPR)cohesion model,a mesoscopic finite element prediction model for the mechanical properties of propellants considering‘dehumidification' damage was constructed.Based on the meso-predictive method of defect-free propellant,the PPR cohesion model was introduced into the propellant particle/substrate interface.The experiment-based inversion optimization method is used to establish an automatic inversion optimization task flow,and eight characteristic parameters of the PPR cohesion model were obtained.By constructing a two-dimensional mesoscopic finite element predictive model considering?dehumidification' damage,the mesoscopic damage evolution process of the propellant was analyzed,and the the mechanical properties such as the propellant Poisson's ratio were predicted based on the model.The results and conclusions obtained in this paper can provide data support and method reference for structural integrity analysis and storage life estimation of solid rocket motor,support the fine evaluation of missile weapon equipment safety and storage life,and have important military value and considerable economic benefits.