基于多尺度动力学分离的结构非线性连接状态诊断

Facing the urgent needs to diagnose local nonlinear joint condition for complicated engineering structural systems and the great challenge of joint identification due to nonlinear, multi-scale and uncertain mechanics behaviors existing on the interface, the proposal presents a new idea combing signal multi-scale decomposition with fast-slow flow modeling of nonlinear dynamic systems. A novel nonlinear joint condition diagnosis method is proposed. Multi-scale signal decomposition is used first to decompose system response into many single-frequency intrinsic mode functions. The physical relation between multi-scale response and system slow-flow dynamics is built. Then, a nonlinear constitute relationship that can describe interface contact condition is developed and used to build system full order model. Model reduction is thus performed to yield a nonlinear reduced model, and model parameters are identified from decomposed multi-scale response signal. Finally, feature parameters are constructed to identify nonlinear joint condition. The two innovation points are building the relationship between multi-scale response decomposition and system fast-slow dynamic processes and presenting a novel joint condition diagnosis method based on identification of the nonlinear reduced-order model.

针对复杂结构系统中局部非线性连接状态诊断的工程需求和因连接界面力学行为具有非线性、多尺度和不确定性的特点而难以进行辨识的科学挑战，本项目提出了将信号的多尺度分解与非线性快慢流动力学建模技术相结合的学术思想，建立了一种结构非线性连接状态诊断新方法。该方法首先对结构宏观动力学响应信号进行多尺度分解，建立不同尺度的波动信号与非线性系统不同快变频率下的慢流动力学模型之间的关系；然后，构造表征连接界面非线性状态的力学模型，并将复杂连接结构的高维非线性动力学模型进行降维；再利用分离出的多尺度信号辨识降阶模型，最终提取出定量表征不同非线性状态的特征参数，实现对复杂结构中非线性连接状态的诊断。项目研究的主要创新点是揭示了信号的多尺度特征与非线性快慢变过程的关联关系，构造了一种利用非线性降阶模型表征接触状态的定量化诊断方法。

立足复杂结构系统中非线性连接状态诊断的工程需求，针对现有连接状态辨识和诊断方法的不足，从接触力学、非线性动力学、信号分析与处理、损伤模式识别等方面开展了研究工作，建立了一种直接利用宏观动力学响应和非线性动力学系统降阶模型诊断连接状态的新方法。项目开展了四个方面的研究：一是提出了一种基于信号的多尺度分解与非线性快慢流动力学建模技术相结合的螺栓连接结构状态诊断方法；二是开展了复杂高维非线性连接结构系统动力学建模和降阶方法研究，重点对连接接合面的非线性降阶建模问题开展了深入研究，提出了多种连接接合面降阶力学模型；三是利用基于信号的多尺度分解与非线性快慢流动力学建模技术相结合的螺栓连接结构状态诊断方法，开展了典型螺栓连接结构预紧力松动识别、松动位置检测试验研究；四是在前述试验研究的基础上，基于所发现的检测灵敏度不高的问题，进一步开展了基于非线性连接结构中超声导波传播的状态诊断技术研究，发展了复杂结构中波传播模拟方法。项目研究为复杂结构系统的健康评估和寿命预测提供理论和方法支撑。