Optimal Design Of Propellant Grain Shape Based On Structural Strength Analysis

Grain design is the core part of Solid Rocket Motor design.Grain design can determin the variation of work pressure and thrust with time,the volume fraction of RSM and the structural integrity of grain is also obtained by determined size of the grain shape,So the stand or fall of grain design determines the interior ballistic performance of the motor and other technical indicators.Under the precondition of grain design satisfying the interior ballistic performance,the researchers usually check the grain design by charging the structural integrity analysis.In fact,the interior ballistic performance of grain is always improved by increasing motor volumetric loading fraction,which lead to poor structural intergrity by reason of increasing the structural response of grain.To solve this problem,through carrying out the research into the application of simulation analysis method and writing the SRM parameterized modeling program,the paper accomplishes structural response analysis and parameter sensitivity analysis.In addition,combined with genetic algorithm,the paper studies grain shape optimization design,including the structural integrity,the change rule of grain burning surface and the filling fraction of grain.At last,combining with the development of analysis software and the cold-air pressurization test,the mechanics properties of the grain are analysed and researched.The proposed methods possess great applicational value for SRM grain design.The main work and achievements are summarized as follows:(1)To achieve SRM parametric modeling functions with secondary development tool Python of ABAQUS,the 3D parameterized modeling program of star shaped grain,wheel shaped grain and wing cylindrical grain is written.The mechanical properties under different load of star shaped grain are obtained through the application of automatically established finite element model.(2)Using 3D parameterized modeling program to star shaped grain,wheel shaped grain and wing cylindrical grain,the sensitivity analysis of grain geometric parameters is carried out with forward difference method.The variations of grain maximum Von Mises strain and ventilated parameter along with the geometric parameters are studied,and the sensitivity coefficients are obtained.(3)Several optimization algorithms are introduced.Throughing grain shape optimization design method combined with GA and SRM parameterized modeling method,the optimumεVmax of star shaped grain,wheel shaped grain and wing cylindrical grain is obtained.Satisfying the demand of burning surface changes and volumetric loading fraction the optimum 3D shape of grain is obtained.(4)Through SRM parametric modeling functions,pressure data of SRM cold pressurization test is directly applied to mechanical performance simulation of grain.The pressure is a non-unifom distribution load in axial direction of grain.Through comparing the simulation results and the experimental results,the reliability and practical of SRM parameterized modeling program is verified.