HHT於結構損壞檢測的應用

Abstract

機械結構的早期損傷預測一直是工業界的重要課題，常見的方法之ㄧ是分析結構的振動訊號，希望由振動訊號的變異得知結構有無損傷，甚至推估得可能的損傷位置。要達到這個目的，必需有適當的訊號處理方法，這個方法需具備良好的解析度和靈敏度以便偵測早期局部微小的損傷。近年來迅速發展的Hilbert-Huang Transform (HHT) 可能提供了一個有效的訊號分析方法。本文主要探討HHT的特性及其在結構損傷偵測的應用。為了簡化問題，用簡支樑代表待偵測的結構，以附加的彈簧代表結構損傷處。利用HHT處理樑的振動訊號，由HHT頻譜的變化判別彈簧存在與否。

The structural damage detection of mechanical structures in the early stage is an important research subject. A commonly used method for this purpose is based on the analysis of the structural vibration signals. Theoretically, the existence and location of the damage can be detected from the variation of the vibration signals. To this end, a proper method for vibration signal process is indispensable. The signal process method should exhibit high resolution and sensitivity for the detection of minor localized damage in the early stage. The Hilbert-Huang Transform (HHT), which has been successfully applied to many different fields in the last ten years, may provide a promising method for this purpose. This thesis studies the properties of HHT and the feasibility of its application to structural damage detection. To simplify the problem, we consider an extremely simply system - a simply supported beam. The damage of the system is represented by a spring with negative stiffness. The vibration signals of the beam with and without the damage are processed by the HHT. The existence of the damage can be identified from the change of the HHT spectra.