Thermostructural Failure Prediction Methodology for Regeneratively Cooled Thrust Chambers

The thermostructural behavior and failure mechanism of regeneratively cooled thrust chambers are fundamental issues when considering reusable liquid-propellant rocket engines. To date, a definitive methodology to fully address this topic is not yet available. This study proposes a methodology based on the numerical integration of the transient thermal problem and the quasi-static structural problem. The most relevant aspects characterizing this methodology are the coupled integration of the thermal and structural equations, geometric nonlinearity, finely tuned isotropic and kinematic hardening models with cyclic tests, a low-cycle fatigue damage model that considers an appropriate multidimensional strain range, and a ratcheting damage model that takes into account the triaxiality of the stress state. This methodology is used to reproduce a test performed on a thrust chamber made of copper alloy subjected to repeated operating cycles until failure. The results demonstrate the ability to correctly reproduce the deformation of the structure and the associated failure mechanism, including the number of operating cycles to failure.