Vibration characteristics of pipe based on panoramic amplitude-fluctuation electronic speckle pattern interferometry

Abstract

The vibration characteristics of inner circular pipe surfaces were determined using the panoramic amplitude-fluctuation electronic speckle pattern interferemetry. A conical mirror was used to collect the inner surface information based on the reflection imaging principle. The planar image was converted into a spatial panoramic view after coordinate transformation, followed by 360° panoramic vibration information reconstruction. The modal measurement was carried out by the proposed method and compared with a numerical simulation and acoustic tests. The results demonstrated the accuracy and feasibility of the proposed method. To understand the influence of defects on vibration characteristics, prefabricated cracks with different lengths along axial and annular directions were introduced. The experimental results demonstrated that annular cracks had little effect on the mode shape. In contrast, the original repetition frequency characteristics were heavily influenced by the axial crack. Furthermore, the vibration modes exhibited veering and the natural frequency decreased significantly owing to the defect.