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Ultrasonic non-collinear wave mixing for the detection of ageing in PVC pipes

Chidambaram, N (2018) Ultrasonic non-collinear wave mixing for the detection of ageing in PVC pipes.

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Abstract:Physical degradation in pipelines made of PVC is caused by a naturally occurring phenomenon called ageing. Physical ageing makes the pipeline brittle, which ultimately leads to its failure. Detection of physical ageing in PVC pipelines is a topic of on-going research as there is no unique method to determine the age of pipelines. Water companies do not know the current state of pipelines in terms of its age and investigations to determine the age of PVC pipelines were made using an ultrasonic inspection technique called non-collinear wave mixing. The non-collinear wave mixing technique involved the interaction between a shear wave and a longitudinal wave under certain resonant conditions, that generated a response longitudinal wave. This thesis reports on the application of the non-collinear wave mixing technique using a different wave interaction, to detect ageing in PVC pipelines. The wave mixing used, involves the interaction between two shear waves that generates a response longitudinal wave. The change in an ultrasonic parameter with respect to ageing time is investigated. The ultrasonic parameter of interest is the difference in amplitude of the generated longitudinal wave at a certain ageing time, with respect to its amplitude at pristine state. In the previous research, the configuration used for the non-collinear wave mixing technique comprised of a receiver placed on the opposite side as that of the transducers sending the pump waves. Both sides of the material had to be accessed and this configuration is called the double-sided access configuration. This configuration was chosen because the ageing-induced changes in the non-linear elastic properties of PVC are small and hence it is difficult to detect these changes only if single-sided access to the material is possible. However, in industries, the material to be inspected is usually embedded and only single-sided access to the structure is possible. Therefore, a configuration in which the receiver is placed on the same side as that of the transducers sending the pump waves is investigated in this research. The extracted amplitudes of the shear pump waves and the generated longitudinal wave are compared in both the configurations. Based on the results obtained, it is found that the amplitude of the shear pump waves and the generated wave changes with ageing time in both the configurations. Therefore, it is concluded that the non-collinear ultrasonic wave mixing technique is sensitive to the phenomenon of physical ageing in PVC. As known from the previous research, it is also concluded here, that the double sided access configuration can be used to detect ageing in PVC. However, it is also found that the single-sided access configuration is sensitive to the phenomenon of ageing and can also be used for its detection in PVC.
Item Type:Essay (Master)
Clients:
Wetsus, Leeuwarden, Netherlands
Faculty:ET: Engineering Technology
Subject:51 materials science
Programme:Mechanical Engineering MSc (60439)
Link to this item:http://purl.utwente.nl/essays/75178
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