基于局部振动模型识别的损伤检测方法研究

发布时间：2018-05-18 09:15

本文选题：虚拟激励 + 结构振动　；参考：《南京航空航天大学》2017年硕士论文

【摘要】：航空航天以及土木等工程结构由于自然灾害或疲劳、腐蚀等会产生不同程度的损伤,经过长期的累积必然会导致结构破坏或使用性能降低。为了提高结构的安全性与可靠性,无损检测技术得到了越来越多的关注。“虚拟激励”法作为一种基于振动与非接触式激光测量技术的损伤检测方法近年来逐渐得到发展,其在检测过程中无需整体结构的振动模型或基准信号。本文基于“虚拟激励”法进行了以下几个方面的研究。首先,深入研究了传统的“虚拟激励”法。针对传统方法需要借助严格的振动微分方程以及依赖结构的力学参数的缺点,在各类板梁理论的基础上,本文提出了一种基于广义振动模型识别的损伤检测方法(General Vibration Model Identification,GVMI)。该方法以多阶微分方程形式描述结构的振动响应,利用最小二乘法拟合方程中的系数,从而建立了结构的广义局部振动微分方程。接着,以铝蜂窝夹层悬臂梁为例建立有限元模型,考虑损伤位于蒙皮和芯层两种情况,定量评估单频点力激励下GVMI方法的损伤检测效果,选取合适的采样间距,提高了其抗噪能力。改变损伤位置,针对出现的检测盲区,探讨两种情况下损伤与位移波长间的关系,分析了两者不敏感区域差异的原因。在此基础上,通过扩展激励频率对GVMI方法进行了优化,确定有效频率范围,将损伤指数进行归一化并对数据进行了融合,消除了检测盲区。最后,搭建了实验平台,利用扫描式激光测振仪采集试件各点的振动位移,对单个与多个损伤分别进行定位,验证了两种损伤方式下GVMI方法的可行性。
[Abstract]:Due to natural disasters or fatigue, corrosion of engineering structures such as aerospace and civil engineering will lead to varying degrees of damage, and long-term accumulation will inevitably lead to structural damage or performance degradation. In order to improve the safety and reliability of structures, nondestructive testing (NDT) technology has been paid more and more attention. As a damage detection method based on vibration and non-contact laser measurement technique, the "virtual excitation" method has been developed gradually in recent years. In the detection process, there is no need for the vibration model or reference signal of the whole structure. In this paper, the following aspects are studied based on the "virtual excitation" method. Firstly, the traditional "virtual excitation" method is deeply studied. In view of the disadvantages of traditional methods which need to rely on strict differential equations of vibration and mechanical parameters of structures, a damage detection method based on generalized vibration model identification is proposed in this paper, which is based on the theory of plate and beam. In this method, the vibration response of the structure is described in the form of multi-order differential equation, and the coefficients in the equation are fitted by the least square method, and then the generalized local vibration differential equation of the structure is established. Then, taking the aluminum honeycomb sandwich cantilever beam as an example, the finite element model is established. Considering the damage located in the skin and core layer, the damage detection effect of GVMI method under single frequency point force excitation is quantitatively evaluated, and the appropriate sampling spacing is selected. The anti-noise ability is improved. The relationship between the damage and the displacement wavelength is discussed in the light of the blind spot of the detection. The reason of the difference between the two insensitive areas is analyzed. On this basis, the GVMI method is optimized by expanding the excitation frequency, the effective frequency range is determined, the damage index is normalized and the data is fused to eliminate the blind area of detection. Finally, an experimental platform is set up. The vibration displacement of each point of the specimen is collected by scanning laser vibration measuring instrument, and the single or multiple damage is located separately, which verifies the feasibility of the GVMI method under two kinds of damage modes.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB523

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