The effect of cracks on the natural frequencies of axi-symmetric vibration modes of gas cylinders

Wake, R.N.; Evans, J.T.

doi:10.1016/s0013-7944(99)00071-5

Cited by 4 publications

(2 citation statements)

References 10 publications

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“…The insensitivity of the longitudinal/circumferential frequencies to the circumferential notch observed above is in agreement with the outcomes of Srinivasan and Kot [10], and also with the fact that orientation of such defects will not break the axial symmetry [11]. This further highlights the advantage of the EMD-EDI method for crack detection in pipeline girth weld.…”

Section: Experimental Emd-edi Results Based On the First Imfsupporting

confidence: 88%

“…This study indicated that the natural frequencies and damping ratios were almost insensitive to the damage while certain mode shapes were affected by the damage. In another study, Wake and Evans [11] investigated the possibility of detection of annular cracks in gas cylinders by using the first few natural frequencies associated with the axi-symmetric modes. They concluded that annular cracks can be identified through relative changes in the natural frequencies of selected vibration modes.…”

Section: Introductionmentioning

confidence: 99%

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Health monitoring of pipeline girth weld using empirical mode decomposition

Rezaei¹,

Taheri‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬²

2010

Smart Mater. Struct.

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In the present paper the Hilbert-Huang transform (HHT), as a time-series analysis technique, has been combined with a local diagnostic approach in an effort to identify flaws in pipeline girth welds. This method is based on monitoring the free vibration signals of the pipe at its healthy and flawed states, and processing the signals through the HHT and its associated signal decomposition technique, known as empirical mode decomposition (EMD). The EMD method decomposes the vibration signals into a collection of intrinsic mode functions (IMFs). The deviations in structural integrity, measured from a healthy-state baseline, are subsequently evaluated by two damage sensitive parameters. The first is a damage index, referred to as the EM-EDI, which is established based on an energy comparison of the first or second IMF of the vibration signals, before and after occurrence of damage. The second parameter is the evaluation of the lag in instantaneous phase, a quantity derived from the HHT. In the developed methodologies, the pipe's free vibration is monitored by piezoceramic sensors and a laser Doppler vibrometer. The effectiveness of the proposed techniques is demonstrated through a set of numerical and experimental studies on a steel pipe with a mid-span girth weld, for both pressurized and nonpressurized conditions. To simulate a crack, a narrow notch is cut on one side of the girth weld. Several damage scenarios, including notches of different depths and at various locations on the pipe, are investigated. Results from both numerical and experimental studies reveal that in all damage cases the sensor located at the notch vicinity could successfully detect the notch and qualitatively predict its severity. The effect of internal pressure on the damage identification method is also monitored. Overall, the results are encouraging and promise the effectiveness of the proposed approaches as inexpensive systems for structural health monitoring purposes.

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Section: Experimental Emd-edi Results Based On the First Imfsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%