Viscoelastic Stochastic Finite Element Analysis And Probabilistic Storage Life Prediction Of Solid Rocket Motor Grain

As the driving force of solid rocket motor,the grain provides propelling power to the rocket through combustion during the rocket ignition and launch phase.The grain is made of viscoelastic composite material,whose stability is relatively low among various parts of the motor,which is more prone to failure and seriously affects the safety and reliability of the solid rocket motor.It can be seen that whether the grain fails during its storage and service is very important for the reliability and life of the solid rocket motor.In engineering,affected by factors such as manufacturing process and raw materials,the material properties of grains normally present unavoidable dispersions,which has shown a great impact on the storage reliability of grains.In addition,when the motor is on duty at sea with the ship,the grain is affected by the environmental loads due to the impact of the waves.Therefore,it is of great significance to reasonably quantify the uncertainty of grain material properties during long-term storage of the motor and the environmental loads under shipborne duty conditions,and to study grain life prediction and reliability assessment methods.Accordingly,this thesis carried out the following work on the uncertainty quantification and life prediction of the performance parameters and environmental loads of the grains in long-term storage and on-board duty conditions:(1)The characteristics of the grain viscoelastic material are explored,and mechanical models are utilized to characterize the linear viscoelastic mechanical behavior of the grain material,and several methods for calculating the deformation value and obtaining the stress distribution of the linear viscoelastic body after being subjected to force are analyzed and introduced.Based on the Schapery model,a new nonlinear viscoelastic model considering cumulative damage is proposed.Model parameters are calibrated and verified by using experimental data of two grain-pillar composite materials,which lays the theoretical basis for the subsequent FE analysis of the grain-pillar structures.(2)Multi-source uncertainty factors of grain material properties and environmental loads are quantified.The random sample data of the stress-strain response of the key parts of the grain model stored for different years and under different working conditions are obtained through FE analysis,which provides data support for the subsequent storage life prediction and reliability analysis of the motor grain under different service conditions.(3)Using the stress-strength interference model,combining the stress-strain response of grain random FE analysis with relevant experimental data,the storage reliability analysis of grain under the influence of material uncertainty is carried out.Based on the Monte Carlo sensitivity analysis,the influence of each random variable on the output of the strain response was quantified;probabilistic fatigue life prediction of solid rocket motor grain under the influence of environmental load uncertainty was conducted using Miner linear damage rule combined with grain S-N curve.