Fatigue Life Prediction of a Rocket Combustion Chamber

Abstract

Cryogenic engines are commonly used in rockets for launching geosynchronous class satellites. The thrust chamber of cryogenic engines is generally of double walled construction. A high conductivity copper alloy is usually selected for the inner wall in regions of high heat flux and for other regions stainless steel is chosen. The failure of a thrust chamber is due to low cycle fatigue, creep of the inner wall, and thermal ratcheting. Present work deals with the study of different plasticity models for the cyclic stress analysis of a double walled cryogenic rocket engine thrust chamber. The work is done using ANSYS (Version 15) finite element code. Different plasticity models used for a simple cubic block showed that a combination of Chaboche's non linear kinematic hardening model in association with multilinear isotropic hardening and creep models is the best suited for cyclic stress analysis of the chamber. Cu-Cr-Zr-Ti alloy is investigated here as it is used in the inner wall of the thrust chamber. Material properties are taken from literature. A comparison of two dimensional (plane strain) and three dimensional cross section of thrust chamber is done. Cyclic life of the chamber is calculated from the cyclic stress-strain graph obtained from above analyses.