Panoramic Amplitude-fluctuation Electronic Speckle Pattern Interferometry And Experimental Investigation On Vibration Characteristics Of Pipe

Tubular structures are widely used in the fields of energy,aerospace,power machinery,and civil engineering.In engineering practice,pipeline vibration is inevitable,and excessive vibration is one of the main reasons for pipeline system shutdown,leakage,fatigue failure,and high noise in industrial facilities.Therefore,exploring the vibration characteristics of tubular structures has important practical significance.Based on the electronic speckle pattern interferometry(ESPI),this paper proposes a panoramic amplitude-fluctuation ESPI system for vibration measurement inside the pipeline,and based on this system,experimental studies have been conducted on the vibration characteristics of aluminum alloy circular pipe and carbon fiber circular pipe with defects.The main research contents of this article are as follows:1.Firstly,the principle of electronic speckle pattern interferometry for vibration measurement is introduced.The use of the amplitude-fluctuation electronic speckle pattern interferometry(AF-ESPI)has performed a vibration measurement from outside the pipe,and the first eight order modal information of the tube is obtained within the frequency range of14000 Hz.Through comparative analysis with simulated vibration modes,found that the AF-ESPI method has shortcomings in pipeline vibration measurement,The specific reasons for the defects of this method in pipeline measurement are analyzed.2.Panoramic amplitude-fluctuation electronic speckle pattern interferometry(PAF-ESPI)for pipeline measurement is proposed,and the imaging principle of a conical mirror reflection system was analyzed in detail.The mechanism of image distortion under the conical mirror reflection system was studied,and the quantitative relationship between the image distortion ratio and the angle of the conical mirror is derived,providing a basis for image restoration.Improved the concentric ring unfolding method to make it suitable for pipeline panoramic restoration,and a program for panoramic reconstruction of conical mirror images is written.Finally,a panoramic vibration measurement of a circular pipe was conducted using the PAF-ESPI system.Considering the impact of actual constraints,a comparative experiment was conducted using the SO Analyzer vibration and noise testing system launched by M+P Company in the United States.Through comparative analysis with simulation and SO Analyzer experimental results,the accuracy and feasibility of this method were proved.3.Firstly,the repetition frequency characteristics of the circular tube mode shape are analyzed based on Donnell’s cylindrical shell theory.On this basis,and prefabricated defect samples in axial and ring directions were selected to study the influence of defect length on the vibration characteristics of circular pipes.In this paper,the vibration mode of the first eight order of the lossless round tube is used as the benchmark,the corresponding modes of the two groups of samples are obtained through experiments,the change law of the mode shape and natural frequency of the round tube is analyzed,and the influence of axial defects and annular defects on the vibration characteristics of the pipeline is explored.The experimental results indicate that circumferential defects have a relatively small impact on the modal shape and frequency.In contrast,axial defects cause the natural frequencies of the repeated frequency mode of the circular pipe to stagger completely,resulting in a significant decrease in resonance frequency.In addition,modal jumping also occur.4.Experimental research on the delamination defects of carbon fiber circular pipe,considering the different distance between the defect location and the inner and outer walls,this chapter improves on the basis of PAF-ESPI system,and proposed an internal and external panoramic amplitude fluctuation electronic speckle pattern interferometry(IEPAF-ESPI)using dual conical mirrors.and proposes a panoramic vibration measurement system of internal and external double conical mirror.In this chapter,the first five modes of three carbon fiber pipe specimens are measured in the frequency range of 14000 Hz.Experimental tests have proven that the IEPAF-ESPI method can effectively improve the accuracy and success rate of defect detection for carbon fiber pipe fittings.