Effect of bulk modulus variation with pressure in propellant grain elastic stress analysis

Abstract

Internal pressurization is one of the critical loading conditions for which structural integrity of solid propellant grains are checked, before using them in service. A direct bulk modulus measurement experiment for propellant material shows that the values of bulk modulus depend on the magnitude of hydrostatic pressure to which the specimen is subjected. In the existing literature, propellant grains have so far been analysed by assuming constant bulk modulus with respect to the rise in internal pressure, during ignition. In this paper we have studied the effect of the variation of bulk modulus with internal pressure in a non-linear elastic stress analysis, using step-by-step finite element method. Numerical results, presented for two practical axisymmetric grain problems, show that the displacements and strains obtained from the non-linear analysis are considerably lower than those obtained from the linear analysis with initial bulk modulus value.