多场耦合条件下功能梯度SMA微结构非线性振动及失稳研究

This study focuses on the nonlinear vibration and instability of the functionally graded Shape Memory Alloy based on Multi-field coupling. The main contents include the following aspects: build the Multi-field coupling model based on the nonlocal strain gradient theory and surface elasticity theory, to considering the size effect and surface effect of the functionally graded SMA micro-wire and micro-film; investigate the influence of size effect and surface effect on the nonlinear vibration and instability; analyze the complex coupling effects of the temperature/mechanical load, geometric nonlinearity and geometric parameters on the nonlinear vibration and instability; simulate the structural mechanics property by multi-field modeling and simulation software; experimental research. The research aims to investigate the effect of the size effect, surface effect, thermal-mechanical coupling, gradient change of thermo-elastic coefficients on the nonlinear vibration and instability of the functionally graded SMA micro-wire and micro-film. This project studies how to improve the nonlinear vibration and instability characteristics of the SMA micro-wire and micro-film by adjusting the gradient of the thermo-elastic coefficients. It aims to provide reliable theoretical basis for the design and optimization of FG-SMA micro devices.

本项目研究将主要集中于考虑尺寸效应和表面效应的热-机多场耦合功能梯度形状记忆合金(Shape Memory Alloy, SMA)微结构的非线性振动和失稳问题，主要内容包括：建立非局部应变梯度和表面弹性微梁、微板多场耦合模型来模拟功能梯度SMA微丝和微薄膜的尺度效应和表面效应；研究尺度效应和表面效应对功能梯度SMA微丝和微薄膜在热-机耦合下非线性振动和失稳特性的影响；考查温度、机械载荷、几何非线性及结构几何参数对非线性振动和失稳机制的复杂耦合影响；对功能梯度SMA微丝和微薄膜进行多物理场模拟和实验验证。主要目的：考查尺度效应、表面效应、热-机耦合和热弹性参数梯度变化的不同形式对功能梯度SMA微丝和微薄膜非线性振动及失稳特性的影响。研究如何通过改变热弹性参数梯度变化的形式调节SMA微丝和微薄膜非线性振动特性及临界失稳特性，为基于功能梯度SMA微器件的设计与开发提供可靠的理论依据。

本课题采取理论分析、数值模拟和实验相结合的思路，考率尺寸效应、材料物性参数、结构尺寸参数、外加载荷等参数的影响，建立能反映热机电耦合工作模式的功能梯度形状记忆合金（FG-SMA）非线性力学模型、FG-SMA相变力学模型，对FG-SMA微结构屈曲、热屈曲、吸合失稳、非线性振动、谐振响应、相变力学等特性进行研究。综合分析了功能梯度材料梯度参数、长细比、初始间隙参数、固定极板形状参数、外加电压、分子间作用力、轴向残余应力、尺寸效应、温度变化等对功能梯度形状记忆合金力学特性的影响。考虑表面效应、材料物性参数、结构尺寸参数、外加载荷等参数的影响，综合分析了功能梯度参数、温度、拉压不对称系数、载荷、截面高度对FG-SMA微梁力学特性的影响。制备FG-SMA试样，完成了实验方案的设计与样品力学性能的测试，结果表明可以通过改变关键参数来提高FG-SMA的相关力学性能及相变特性。本项目研究成果对针对性设计新型FG-SMA器件具有重要理论意义，同时可以促进多场耦合力学的发展。