Design of compliant thermal actuators using topology optimization involving design-dependent thermal convection and pressure load

This study presents a topology optimization method for thermal actuators that accounts for boundary conditions influenced by variables such as thermal convection and pressure load. Thermal actuators with gripper-like designs are essential for handling hot and brittle materials. The objective of this study is to design actuator shapes that achieve an optimal balance between flexibility and stiffness in high-temperature environments. Unlike previous studies that consider load conditions imposed on fixed boundaries within the design domain, this research introduces a high-temperature fluid as the driving source and employs a novel approach to boundary condition setting by integrating fictitious physical problems. This approach allows for the precise specification of various boundary conditions across multiple domains. A weighted-sum method is applied to optimize three objective functions related to deformability, stiffness, and thermal diffusibility of the actuators. To address the issue of excessively thin structures compromising deformability and the poor convergence of the optimization process, stress constraints based on the optimization history are introduced. The proposed method is validated through numerical examples, demonstrating improvements in structural deformability while controlling deformation on the target surface plane. The numerical results confirm that the objective function decreases and stress is suppressed, verifying the effectiveness of the proposed approach.