SMA复合式结构优化设计及实验验证
OPTIMAL DESIGN AND EXPERIMENTAL VALIDATION OF SMA HYBRID STRUCTURE
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摘要: 大涵道发动机外涵尾喷智能锯齿通过在“偏转-恢复”两种稳定形状之间按需转换, 实现发动机降噪与燃油经济性的有机统一. 这种具有“偏转-恢复”功能的变形结构, 其服役性能主要由变形前后的稳定姿态决定, 其中间转化过程涉及极端复杂的高度非线性过程, 但对实际性能影响不大. 为此, 本文针对这一典型结构提出了一种简化的SMA复合式结构驱动力模型及优化设计方法. 通过将充分冷却、充分加热的SMA分别等效为不同模量的线弹性材料, 针对偏转前后两种稳定状态的差值进行结构优化设计, 避免了优化方法必须考虑复杂非线性本构的弊端. 完成了面向航空发动机智能锯齿的仿真及优化设计. 采用GCMMA算法进行优化计算, 根据得到的优化结果, 制作了两种构型的锯齿样机, 其中锯齿“偏转-恢复”尖端偏转比(尖端偏移量/锯齿长度)分别达到了8.27%和9.04%.Abstract: This study focuses on the optimization of outboard chevron smart serrations, which represent a typical morphing 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" 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 morphing 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.
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