Shape Improvement And Optimization Of Solid Rocket Motor Grain Based On Structural Integrity Analysis

During the Solid Rocket Motor (SRM) design, grain design is the core section. Theaim of grain design is to scheme out reasonable grain configuration after the suitablesolid propellant material is defined. However, in the design process of grainconfiguration, the interior ballistic performance is usually paid more attentions, and thestructural integrity of SRM is not given enough considering but only used to assess thedesign passively. In fact, the grains with excellent interior ballistics performance alwayshave high volumetric loading fraction, and this will lead to poor structural intergritybecause of high structural response. To resolve this confliction, correlative methods andapplications are studied in this dissertation. Based on summarizing the process of SRMstructural integrity analysis systematically, SRM parameterized modeling method isproposed and applied to the grain shape improvement and geometric parametersensitivity analysis. Moreover, combining this method with Genetic Algorithm (GA),the grain shape optimization is conducted taking structural integrity and volumetricloading fraction into account. The main work and achievements are summarized asfollows:Based on Herrmann variation principle, a viscoelastic incremental Finite ElementMethod (FEM) is developed, which is suitable for structural analysis of grain subjectedto variational temperature load. Structural integrity criterions of SRM are ascertained,which can satisfy the needs of engineering application. The research work provides thefoundation for structural analysis and integrity assessment of SRM.SRM structural integrity analysis method and general processes using CAEsoftware are summarized. The structural integrity analysis is completed for a certainSRM. Grain shape improvement method based on the structural integrity analysis isinvestigated and the improved project that fulfils structural integrity requirement isderived. The application shows that SRM structural integrity analysis and grain shapeimprovement method are practical and feasible.SRM parameterized modeling method is proposed. The specific techniques withsecondary development tool Patran Command Language (PCL) of MSC.Patran areresearched. Taking the star shape SRM for example, the finite element model can beautomatically established with geometric parameters and the processing of analysis andresult can also be controlled with corresponding parameters. The working efficiency isimproved obviously through the application for grain improvement of star shape SRM.The parameterizations for two-dimensional finite element model of conocyl SRM,star shape SRM, wheel shape SRM, and three-dimensional finite element model offinocyl SRM are realized. The sensitivity analysis of geometric parameters for the grain configuration is carried out with central difference method. The variations of grainmaximum Von Mises strain and volumetric loading fraction along with the geometricparameters are studied, and the sensitivity coefficients are obtained. At last, the keygeometric parameters are chosen for grain shape optimizations.Mathematical mode of the SRM grain shape optimization is established and theimplementation techniques of GA are discussed. The grain shape optimization methodis put forward by combining with GA and PCL parameterized modeling technique. Thegrain shape optimization with considering both of grain structure integrity andvolumetric loading fraction is completed and the optimum axial section shape ofconocyl grain, the optimum cross section shape of star shape grain and wheel shapegrain, and the optimum three-dimensional shape of finocyl grain are obtained.In conclusion, the SRM grain shape improvement and optimization consideringboth of the structural integrity and volumetric loading fraction are successfully executedin this dissertation, at the same time, some developments in applications and methodshave been attained. The acquired results can provide more comprehensive references forSRM grain design. The proposed methods possess great applicational value for SRMgrain configuration design and can be applied to similar complex sturcture shapeoptimization conveniently.