Three-dimensional Finite Element Analysis on The Connecting Structure between Back-joint and Fixed body of Solid Rocket Motor

Paper number

IAC-05-C2.6.08

Author

Ms. Yu Fan, Academy of Aerospace Propulsion Technology, CASC, China

Year

2005

Abstract

The bolt connecting structure between back-joint of the composite case and fixed body of nozzle is always the noticed focal point and analyzed difficult point in the structure analysis of SRM. Many features such as combination of various materials, contact of diverse interfaces and large deformation of geometric nonlinearity are possessed by this structure. So it is difficult to analyze this problem accurately and effectively at present. Theoretical researches only get qualitative and semi-quantitative results. The stresses and deformations about the connecting structure under the interior pressure are analyzed detailedly and precisely by means of MARC software based on three-dimensional finite element theory in this paper. The thickness of the major edge flange about fixed body is adjusted to ensure the reliable sealability and cut down the inert mass of the connecting structure, which has important significance to improve the function of entire SRM.
    Depended on one SRM model, the composite case is simplified to be regarded as orthotropic material and dealt with large deformation of geometric nonlinearity. The plastic properties of metal materials are considered sufficiently and interaction relations of components have been defined rationally especially gliding contact boundary(considering friction). The calculations of three coupled nonlinearities about geometric nonlinearity, elastic-plastic property and contact are carried out. Under the condition that other dimensions of the structure are not changed, the thickness of the major edge flange about fixed body is adjusted and several models of different thickness between 20mm and 40mm are calculated and contrasted .The results show that the variation of thickness has minor influence to the deformation of the structure, but has major influence to the stresses of every components especially the open angle between fixed body and back-joint. As far as this SRM, when the thickness is less than 25mm, open angle is at the inside of the interface and increases constantly along with the reduction of the thickness, which makes the airproof to be disadvantageous extremely. When the thickness is more than 25mm, open angle is at the outside of the interface. Although the thickness is more larger more advantageous to the airproof, it is too thick not only increasing the mass but improving the bending stresses of the entire motor, which is unfavorable to the connecting structure. Therefore, the thickness of the major edge flange about 25mm is the most optimized design as the intensity and stiffness of this structure are supplied. 
    Three coupled nonlinearities problem is dealt with on three-dimensional finite element model of SRM for the first time in this paper. The approach way of designing model, the method of processing problem and the exploit to MARC software all adopted in this paper lay a good foundation in this field. The analytic results and conclusions have certain reference meaning to designers and can offer theoretical datum to the synthesis test check of products.

Abstract document

IAC-05-C2.6.08.pdf

Manuscript document

IAC-05-C2.6.08.pdf (🔒 authorized access only).

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