Investigation On Closed-crack Detection In Pipeline Using Vibro-acoustic Modulation Technique

Under the high temperature, high pressure and alternating loads, industrialpipeline occurs Fatigue cracking which may endanger the pipeline’s safety and stableoperation. And closed crack is a kind of great danger of crack in the pipeline.In the industrial production, even a small crack, which is in the environment ofthe alternating stress, the high temperature and the corrosion conditions, will soonbe extended, and suddenly ruptured, by the failure occurs. Closed crack has become asignificant risk of affecting the normal production of industrial. Therefore, theresearch of pipeline closed crack detection method has very important engineeringsignificance. In this paper, the pipeline’s closed crack detection method based onvibro-acoustic modulation technique has been studied. The main work includes:(1) Parameter impact study for vibro-acoustic modulation detection. Based onsimplified theoretical model to analyze the influence of test parameters on thevibro-acoustic modulation detection. On this basis, focusing on the influence of thevibro-acoustic modulation pipe’s closed crack detection parameter test, and analysisthe influence of vibration amplitude and ultrasonic amplitude. Optimization electedthe vibro-acoustic modulation parameters.(2) Vibro-acoustic modulation characteristic parameter characterization methodstudy based on wavelet transform. The wavelet transform is applied to four types oftypical simulation modulated signal (linear amplitude modulation, extreme amplitudemodulation, frequency modulation and mixed modulation) feature analysis todetermine the parameters of the wavelet feature can be used for the identification offour types of classes modulation signal. The results shows that the pipeline’s closedcrack vibro-acoustic modulation are amplitude modulation, but because of thelow-frequency vibration amplitude is too large and often occurs amplitudemodulation.(3) The trial study of the crack quantitative evaluation in vibro-acousticmodulation crack detection. Studies the crack quantitative evaluation of sidebandamplitude, mainband amplitude, MI and frequency components of instantaneousamplitude signal obtained by wavelet transform. The results show that frequencycomponents of instantaneous amplitude signal obtained by wavelet transform can bequantitative evaluate crack.