Life Prediction of Rocket Combustion-Chamber-Type Thermomechanical Fatigue Panels

Abstract

Thermomechanical fatigue panels represent small actively cooled sections of the hot-gas wall of a regeneratively cooled liquid rocket engine. In combination with cyclic laser heating, the panels are used to study both the fatigue life and thinning and bulging phenomena (the so-called doghouse effect) without the need for testing a full-scale engine. To improve the prediction of the thermomechanical fatigue panel’s fatigue life, a viscoplastic model coupled with isotropic damage and thermal aging was implemented. The temperature-dependent material parameters are determined using experimental data to take into account softening effects due to material degradation. The number of cycles to failure is computed numerically and compared to the results of a thermomechanical fatigue panel test. The damage parameter-based finite element analysis successfully predicts the damage initiation point in the middle cooling channel of the thermomechanical fatigue panel. Critical damage occurs at the 150th cycle, whereas the failure is experimentally observed at the 174th cycle. The effect of the increase of the wall thickness in the fin areas is also obtained by this numerical analysis. This study shows that cost-efficient thermomechanical fatigue panel tests have the potential to validate numerical fatigue life predictions for novel rocket combustion-chamber wall materials.