OPTIMAL DESIGN AND EXPERIMENTAL VALIDATION OF BISTABLE SMA HYBRID STRUCTURE

This study focuses on the optimization of outboard chevron smart serrations, which represent a typical bistable structure for high-bypass ratio engines. It achieves a balance between engine noise reduction and fuel economy by utilizing chevron serrations to transition as needed between the "deflected" and "recovered" stable states. The performance of this "deflected-recovered" bistable structure is primarily determined by its stable configurations before and after deformation during service. The transformation between these two configurations involves highly complex nonlinear behavior but has minimal impact on overall service performance. This study proposes a simplified actuation force model and an optimization design method for this typical bistable structure. The SMA is treated as a linear elastic material with different equivalent moduli at varying temperatures, and structural optimization is performed based on the difference between the two stable states (before and after deflection). This approach circumvents the challenges associated with the complex nonlinear constitutive behavior of SMA transformation. The simulation and optimization design for the chevron smart serrations were completed using the GCMMA algorithm. Based on the optimization results, two prototypes of chevron configurations were fabricated and tested, achieving tip deflection ratios ("deflected-recovered" tip offset/chevron length) of 8.27% and 9.04%, respectively.