Finite element analysis, design and experiment on solid propellant motors with a stress reliever

Abstract

The results of an investigation on solid propellant motors with a stress reliever are presented. The thermal stress and strain of solid propellant motors during service life were analyzed by means of MSC/NASTRAN using eight-node HEXA solid elements. Three design cases of a stress reliever were considered to study its effects on the reduction of thermal response. On the other hand, two additional design cases, with an alternative free-flap design or without any thermal stress relief design, were also analyzed for comparison. Verification of the analysis results was accomplished by applying the nondestructive test (NDT) after three cycles of thermal loading. Good correlation existed between the computational and experimental results when the corresponding failure location and failure mode of the solid propellant were compared. Two important design criteria are established. One is on the minimum outer diameter of the stress reliever, which dominates the hoop stress. The other is the maximum outer diameter of the stress reliever, which controls the axial normal stress.