Finite Element Analysis Using Herrmann Formulation for Viscoelastic Materials

Abstract

The structural design and development of Solid rocket motor (SRM) is currently based on method of casting solid propellant grain into a metallic or composite casing. In general, SRM is subjected to diverse loading conditions during transportation, storage and firing, due to which cracks may be developed in solid propellants because of excessive loads. Finite element analyses (FEA) based on displacement method, were conducted in order to determine the integrity and the ultimate service life of solid rocket motors. The displacement based finite elements have the limitation of evaluating the distribution of stress and strain on the solid propellants which are viscoelastic in nature. In this paper, a finite element study based on Herrmann formulation is discussed to overcome this limitation in which 8- node quadrilateral,9-node quadrilateral and 6-node triangular axisymmetric finite elements have been developed and analyzed for stress and strain distribution for head and mid segments of solid propellant rocket motor subjected to thermal loading. Results obtained from present study are compared to that obtained using MARC, commercial FEA software.