Microstructure-sensitive thermomechanical deformation and life assessment of the regeneratively cooled thrust-chamber inner wall: A temperature-dependent crystal plasticity approach

To clarify the thermomechanical deformation mechanism and improve the life prediction accuracy of the regeneratively cooled rocket thrust chamber inner wall, a temperature-dependent crystal plasticity finite element method (CPFEM) considering grain morphology effects is developed for the copper-alloy inner wall. Sequential thermomechanical simulations are performed under representative service loading conditions. The results show that cyclic thermomechanical loading induces pronounced ratcheting deformation, and the comparable length scale between grain size and inner wall thickness leads to strong deformation heterogeneity. Localized compressive shear bands form along specific grain paths during heating and remain after cooling, resulting in asymmetric deformation about the inner wall centerline that cannot be captured by conventional homogeneous constitutive models. Simulations of multiple random polycrystalline models reveal significant scatter in strain localization and critical deformation locations, highlighting the dominant role of grain morphology and crystallographic orientation in failure evolution. Life evaluation based on ratcheting and low-cycle fatigue damage indicates that ratcheting is the primary damage mechanism. Compared with the traditional homogeneous model, the proposed CPFEM successfully captures the stochastic and asymmetric strain localization of the thrust chamber inner wall and predicts markedly higher localized plastic strains and substantially shorter service life, which is qualitatively aligned with the “doghouse” type failure characteristics reported in the literature. This work provides a microscale-based approach for accurate deformation analysis and life prediction of thrust chamber inner walls, supporting the structural design and reliability evaluation of reusable rocket engines.