Ultrasonic inspection of highly attenuating media

• Main Author: Egerton, Jack Samuel
• Other Authors: Lowe, Michael ; Huthwaite, Peter
• Published: Imperial College London 2018
• Subjects: 621
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.754760

The aim of the project was to improve the ultrasonic array inspection of high-density polyethylene (HDPE) heat-fused pipe joints of cooling water pipework that is installed in EDF Energy's nuclear power stations. Whereas ultrasound array inspection is now established for safety-critical metal components, HDPE poses a hugely challenging problem, that the ultrasound waves are heavily attenuated by the material. This impacts multiple aspects of the inspection and of the modelling that is needed to design and qualify inspection. The thesis reports a range of research that was needed to overcome this challenge. The work of the thesis has: - obtained accurate acoustic properties of HDPE that are necessary for improved simulated or real ultrasonic array imaging of HDPE pipe joints - developed a simulation technique for representing ultrasound in such inspections that has both high accuracy and efficiency - extended analytical analysis of ultrasound scattering from cylindrical voids from elastic media to general, attenuative media - used the Huygens-Fresnel principle to represent ultrasound scattering from volumetric and planar voids, to image sub-wavelength features of these defects in an ideal circular array setup, and to image angled ultrasonic array nondestructive evaluation (NDE) of potential defects occurring in HDPE pipe joints - devised an automated and antidispersive system for reducing coherent and incoherent noise in waveforms with an isolated wave reflection signal - produced an imaging and analysis method for ultrasonic array NDE that can represent defects in a refractive, reflective, and scattering environment in attenuating media, which is applied to data from the above developed simulation technique - applied much of the above imaging and analysis method to defects machined into HDPE pipe material, with an experimental ultrasonic array controller, yet with an array of limited suitability - specified parameters for ultrasonic arrays and a water-filled wedge, which are optimum for HDPE pipe joint inspection, and have been designed and built by Imasonic SAS, France, for research use at Imperial College London.