Abstract
There is an increasing interest in using ultrasonic guided waves to assess the structural degradation of above-ground storage tank floors. This is a non-invasive and economically viable means of assessing structural degradation. Above-ground storage tank floors are ageing assets which need to be inspected periodically to avoid structural failure. At present, normal-stress type transducers are bonded to the tank annular chime to generate a force field in the thickness direction of the floor and excite fundamental symmetric and asymmetric Lamb modes. However, the majority of above-ground storage tanks in use have no annular chime due to a simplified design and/or have a degraded chime due to corrosion. This means that transducers cannot be mounted on the chime to assess structural health according to the present technology, and the market share of structural health monitoring of above-ground storage tank floors using ultrasonic guided wave is thus limited. Therefore, the present study investigates the potential of using the tank wall to bond the transducer instead of the tank annular chime. Both normal and shear type transducers were investigated numerically, and results were validated using a 4.1 m diameter above-ground storage tank. The study results show shear mode type transducers bonded to the tank wall can be used to assess the structural health of the above-ground tank floors using an ultrasonic guided wave. It is also shown that for the cases studied there is a 7.4 dB signal-to-noise ratio improvement at 45 kHz for the guided wave excitation on the tank wall using shear mode transducers.
Highlights
Structural Health Monitoring (SHM) of engineering structures using ultrasonic guided waves is a rising area of interest
Worlton [2] and Viktorov [3] explored the potential of Lamb and Rayleigh waves to inspect plate-like structures non-destructively and the market interest led to ultrasonic-guided wave testing being commercialized for pipe inspection in 1994 [4,5]
Finite Element Analysis (FEA) was performed to study the potential for guided wave excitation from the tank wall to assess the structural health of the tank floor
Summary
Structural Health Monitoring (SHM) of engineering structures using ultrasonic guided waves is a rising area of interest. Much research has been conducted on the use of ultrasonic guided waves to inspect elongated engineering structures, i.e., pipes, plates, rails, and cables, because of their inherent long range propagation [1]. Much research has been conducted on the inspection of above-ground storage tank floors using guided waves. The fundamental shear horizontal mode is an interesting alternative to the fundamental symmetric mode due to its non-dispersive characteristic Another factor to consider is the welding seam, which reflects the transmitted signal and disturbs the propagation. This study investigates the potential for using the tank wall to bond transducers for SHM of tank floors using guided waves. Both normal and shear loads were considered in this study.
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