The effect of nonlinearities on the strain concentration factors in solid propellant grains

Abstract

Maximum induced strains in slotted and star grains are obtained from the inner bore hoop strain of a simple hollow cylindrical grain, by applying strain concentration factors (SCF), during preliminary grain configuration design. Here, the effect of certain inherent material and geometric nonlinearities on the SCF is studied through a step-by-step nonlinear finite element analysis of grains, for ignition pressurization load. The material nonlinearity considered here is due to the presence of internal voids in the grain material which induce nonlinearity in the behaviour of bulk modulus with respect to the magnitude of hydrostatic pressure. Under geometric nonlinearity, grain deformations are taken into account at each load step of the step-by-step finite element analysis. Results show that the effect of nonlinearities on the SCF is quite considerable.