| Solid rocket motor combustion chamber metal shell is its principal part,and all functions of rocket propulsion system rely on it.This task is on the support of power promotion project of the Institute.The paper aims at the structural strength of finite element simulation of rocket metal shell and provides an effective analysis method.Meanwhile under using the analysis method,the scope of structural response is carried out based on the uncertainty range of material parameters and geometry parameters.This would provide the reference for the threshold judgment about the finite element simulation analysis results in practical engineering.The research content includes that:First,this paper describes the structure and typical characteristics of metal shell,introducing typical fault and failure mode using traditional analytical method and the current problems existing in the metal shell finite element analysis.Secondly,material elastic-plastic constitutive equation is established in this paper using classical Prandtl-Reuss flow rule.According to the actual engineering requirements,elastic-plastic constitutive equation is simplified to multi-segment polynomial equation.30Cr3 high strength steel material static mechanics performance curve is received from material single tensile test at room temperature.Using statistical methods,the material elastic modulus,stress and strain data on the plastic stage would fit curve and the constitutive equation would gain.It has been verified by the simulation analysis that the material parameters which determined by the statistical method brings error within 5.4% to the result of strength finite element analysis.And then,through the analysis of finite element analysis method including the comparison with implicit and explicit algorithm,different selection of unit,different mesh generation and different model simplification,this paper confirms that choosing implicit algorithm is suitable for metal shell finite element analysis.The increase of unit order and the layer of grid will directly improve calculation accuracy.While considering computational efficiency,secondary reduced integral unit is a good choice.In the radial direction of metal shell,at least two layer of grid should divide in order to ensure reasonable calculation error.In the aspect of model simplification,large opening B thread recommends the use of the whole thread model in strength finite element analysis.The pin for connection positioning and locking can ignore because it doesn’t affect the results of the analysis.It has been verified by a metal combustion chamber shell model that this method of finite element analysis is effective.At last,the scope of structural response considering uncertainty range of material parameters and geometry parameters is researched by single factor and integrated factor test.This paper ensures that the material parameters of shell are the main factors to the structure response,and the thickness parameters of shell are as followed.Failure case analysis proves that parameter uncertainty interval brings 20% error to the results of structural response.Through fault recurrence of a metal shell,it is founded that the structural stress is not within the available error range,and then leads to the failure.Lately,due to the analysis of the optimized model,the error is in the range of allowable deviation,so the structure design is feasible.The study aims to provide a feasible and high precision structure finite element analysis method for metal chamber shell and ascertain the deviation affection from parameter uncertainty interval,which will bring practical value for metal shell design. |
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