Abstract
The crack which appears in the structure can be described by a local flexibility. With the occurrence and propagation of crack, the local flexibility will change. The change can effectively reflect the damage degree of the structure. In this paper, the measurement method of the crack local flexibility of the beam structure is presented. Firstly, a series of sample points are selected at the crack location and the possible value range of the crack local flexibility, and then these sample points are used as input parameters for the dynamic analysis of the beam structure. The vibration equation of beam structure is solved, and the frequency influence surface is drawn. In addition, the vibration signal of the beam is tested, and the first three order natural frequencies can be obtained. Thirdly, these frequencies measured are adopted to cut the natural frequency influence surfaces, and then the first three order natural frequency influence curves are drawn. The intersection points of these frequencies influence curves can indicate the crack local flexibility and the corresponding crack location. This method is suitable for measuring the local flexibility of crack with different shapes and types in the beam structure which have various cross sections.
Highlights
Structural damage is usually manifested firstly as the appearance of structural cracks and expands under the long-term external load [1,2,3]
To ensure the safety and reliability of structures, researchers have developed many structural damage detection methods [4,5,6,7], such as acoustic emission, ray detection, and magnetic flux leakage detection. e crack which appears in the structure can be described by a local flexibility
The common crack models include the crack model based on the equivalent drop-section method [8], the crack model based on the principle of uniform crack beam [9, 10], and the crack model based on local flexibility [11,12,13,14,15,16]. e crack model based on local flexibility is established by the fracture mechanics theory and the introduced local flexibility
Summary
Structural damage is usually manifested firstly as the appearance of structural cracks and expands under the long-term external load [1,2,3]. E crack model based on local flexibility is established by the fracture mechanics theory and the introduced local flexibility. Liu et al [16] established a cantilever beam model with horizontally embedded cracks and analyzed the effect of crack local flexibility on the first three order natural frequencies and modes of the structure. Most of these studies have focused on the solution of crack local flexibility.
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