RESEARCH ON AXISYMMETRIC THERMO-MECHANICAL COUPLED TOPOLOGY OPTIMIZATION OF CERAMIC MATRIX COMPOSITE TURBINE BLISKS

To address the lightweight and high-stiffness design of continuous fiber-reinforced ceramic matrix composite (CMC) turbine blisks under high rotational speeds and specified temperature fields, an axisymmetric thermo-mechanical coupled topology optimization method considering thermo-mechanical topology-dependent loads and maximum size constraints is proposed. Based on the feature that the radial and circumferential directions are the primary load-bearing directions of the turbine blisk, continuous fibers are assumed to be arranged along the radial and circumferential directions, respectively, and the CMC is modeled as a temperature-dependent orthotropic material. Utilizing the characteristics that the 3D blisk’s geometry, material distribution, and primary loads are uniformly distributed along the circumferential direction, a 2D axisymmetric thermo-mechanical coupled finite element model under a given temperature field is established using the meridional plane of the blisk as the analysis domain. To account for the dependency of centrifugal loads and thermal expansion equivalent loads on material layout, the RAMP model is employed to interpolate the material stiffness and topology-dependent loads. The mean square value of the radial displacement at the outer rim boundary nodes is defined as the objective function to characterize the rim deformation level under combined thermo-mechanical loading. Furthermore, considering the limitations imposed by the chemical vapor infiltration (CVI) process of CMCs on the feature size of local blisk components, a Helmholtz partial differential equation filter is adopted to construct local material aggregation measures, and an Augmented Lagrangian Method is combined to handle large-scale local maximum size constraints. A mathematical formulation for the topology optimization problem is established, comprehensively considering the thermo-mechanical coupled deformation response and maximum size control of the CMC turbine blisk. The sensitivity information is derived using the adjoint variable method, and the optimization problem is solved via mathematical programming algorithms. Numerical examples analyze the effects of the specified temperature field, rotational speed, volume fraction, and maximum size control parameters on the optimized layout and rim displacement level. The results demonstrate that changes in the temperature field primarily affect the rim displacement level, whereas rotational speed and volume fraction exert a more significant influence on the main load-bearing paths and topology. As the rotational speed increases, the optimized blisk layout gradually transitions from a single-web to a double-web load-bearing configuration. Maximum size constraints effectively suppress excessive local solid material aggregation and alter the distribution of the load-bearing paths. The proposed optimization method provides a helpful reference for the conceptual design of CMC turbine blisk structures.