The Role of Cyclic Plasticity on the Low-cycle Fatigue Performance of the Space Shuttle Main Engine Steel Components

Kristine Cochran, University of Illinois

The demanding operating environment of the Space Shuttle Main Engine (SSME) can lead to the development of low-cycle fatigue cracks in the steel components. Low-cycle fatigue refers to the application of high loading levels in a cyclic manner such that the life of the component may be less than 10,000 cycles. The environment of the SSME is characterized by high operating temperatures, extreme temperature gradients and severe pressure fluctuations. Successful modeling of low-cycle fatigue crack growth in such an environment depends directly on the ability to predict stress states accurately near the crack tip.

Current research is focused on the development and implementation of material models capable of accurately and efficiently modeling the cyclic inelastic response of the stainless steel components. As a first step, the Frederick-Armstrong model has been implemented into WARP3D, a three-dimensional finite element code developed by Professor Dodds at the University of Illinois specifically for large-scale fracture mechanics applications. The main features of this cyclic plasticity model, key issues in its implementation, and preliminary results from its use in fatigue analysis will be presented.

Abstract Author(s): Kristine B. Cochran