Reliability Analysis For Grain Of Solid Rocket Motor

A solid rocket motor is a complicated system which can be used only once and can not be repaired. Because of the effect of the random factors such as high temperature, high pressure, high heat flow and so on, the motor is prone to fail when it has inherent defect in its structure. The reliability problem of a solid rocket motor has been highly considered, and especially probability design has already become a necessary chain in designing and manufacturing solid rocket motors.As a significant ingredient of a solid rocket motor, the structural reliability of the solid rocket motor grain can directly influence the reliability of the whole solid rocket motor.Using the basic theory of viscoelasticity, with plane strain presumption as premise, analysis of stress-strain of solid rocket motor grain under pressure during ignition, temperature decrease during solidification and axial load has been made respectively. Analysis of axial strain and deformation of grain under axial load has been made. Study on the failure performance and criteria of grain has been made. In view of the situation in which solid rocket motor grain is affected by both temperature decrease during solidification and axial load, strain analysis has been made by regarding inner grain surface micro unit as in three-dimensional stress and a safe clearance equation has been established, based on octahedron shearing strain standard. Based on AFOSM (1), a case of grain being affected by both temperature decrease during solidification and axial load is calculated. The calculation result shows the reliability of inner grain surface descends with the decrease of grain temperature.The conclusion will be of practical value on the structural reliability assessment of solid rocket motor grain, the above research method can also be used for the reliability analysis of other viscoelastic materials.