Research On Damage Detection Based On Hilbert-Huang Transform

Structural health monitoring system is an important research direction in the hot area of smart material and structures. And composite damage detection is an important research content of structural health monitoring. In chapter one, the research discusses the concept and development of structural health monitoring. Then raise the question about the key part of SHM-signal processing method. In chapter two, the paper studied the concept of active monitoring technique based on Lamb Wave, and the propagation fundamentals of Lamb wave in structure. The idea of time delay estimation methods is also mentioned in the paper. In chapter three, a new signal processing tool-Hilbert Huang Transform(HHT) is introduced in detail. This method transcends the usual signal processing methods, such as Fourier Transform, and is proved to be ideal for non-lineal and non-stationary data. The paper also gives several examples to demonstrate this point. In chapter four, Damage Localization system for composite materials based on lamb wave methods using HHT is discussed in detail. According to the composite material, the amplitude of Lamb wave before and after damage's generation is compared, and the diminishment is seen as a judging standard to determine whether there is damage in the plate or not. Furthermore, HHT technology can be applied to determine damage location. This study adopts active detection technique based on Lamb Wave to monitor damage in composite materials. PZT ceramics with the diameter of 8mm are bonded on the surface of fiberglass-reinforced composite material acting as both actuators and sensors to generate and collect Lamb waves. The waves emitted interact with discontinuities and experience a change in their propagation characteristics when damage is generated. By comparing sensor signals collected before and after damage happens, the location of damage in one-dimensional structure can be determined.