Simulation of dynamic fracture events in solid propellant rockets

This paper summarizes the formulation, implementation and preliminary application of an axisymmetric aeroelastic coupling algorithm specially developed to simulate the complex phenomena associated with dynamic fracture events taking place along the case/grain interface during the flight of a solid propellant rocket. The coupling approach combines an explicit cohesive/volumetric finite element (CVFE) scheme used to model the spontaneous initiation and rapid propagation of the interfacial crack, with an unstructured adaptive finite volume fluid solver able to capture the geometrical changes taking place in the fluid domain due to the crack motion and the large grain deformations. An Arbitrary Lagrangian/Eulerian (ALE) formulation is also adopted for the solid solver to account for the regressing boundary of the solid propellant. Nonlinear kinematics is used to describe the motion of the grain to account for the possible large deformations and rotations associated with the dynamic fracture process. The constitutive response of the grain is characterized by the Arruda-Boyce nonlinear model. Two applications illustrating the capabilities of the aeroeiastic code are presented in this paper: the first one is concerned with the motion of an inhibitor protruding in the core flow, and the second with the Titan IV SRMU grain collapse incident.