Structural Reliability Analysis For Viscoelastic Materials Of Solid Propellant

The safety of a solid rocket motor, which serves as the propulsion system and the key component of a solid missile or a space aircraft, is extraordinary important. Since long term, the reliability problem of a solid rocket motor has been highly considered, and especially probability design has already become a necessary tache during designing and manufacturing solid rocket motors. The structural reliability of a solid rocket motor grain, which is a significant ingredient of a solid rocket motor, can directly influence the reliability of the whole solid rocket motor. So it is very necessary to do research in the structural reliability of solid rocket motor grains.In this paper, applying an integral expression of linear viscoelastic theory, several integral equation expressions for obtaining shear modulus G(t) from stress relaxation modulus E{t) and bulk modulus K(t) are acquired by using inversion of the Laplace Transform. And then a numerical integration method of obtaining G(t) from given experimental data of E(t) and K(t) is presented by means of iteration and numerical integration. On the basis of the unified constitutive theory of three-dimensional linear viscoelasticity, the concrete and incremental viscoelastic constitutive equation, which has extensive use, and the responsible finite element format are both deduced. Making use of ANSYS, the viscoelastic responses under vary work conditions like temperature loads, inner pressure and axial overload are successfully simulated. The thesis, using instant reliability and based upon ANSYS Probability Design, has done the random analysis of a viscoelastic plate under unit step loading, and has analyzed the reliability of a grain under temperature decreasing during solidification, and that of the grain under inner pressure during ignition. Using frequency-domain analysis of multi-axial fatigue based upon equal Von Mises stress, and combined with random vibration analysis function of ANSYS, the structural fatigue cumulative damage and the fatigue reliability of one solid rocket motor grain, which is excited by random vibration loads during road transportation, are calculated.