Thesis
Considerations for an in-process ultrasonic phased array inspection method for narrow gap welds
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2024
- Thesis identifier
- T17037
- Person Identifier (Local)
- 202055239
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- The nuclear industry in the UK has seeing a resurgence in recent years, joining the race to net-zero energy production through renewable sources. This has led to an increasing demand for the modernisation of manufacturing processes for high-value welded components, such as nuclear pressure vessels and offshore turbine towers. To ensure the structural integrity of these critical components, Non-Destructive Testing (NDT) is often an essential step in the manufacturing process. Currently, NDT of welds are conducted after the welding process and often off-site, with detected defects requiring rework often resulting in schedule delays. However, by combining the welding and inspection processes at the point of manufacture, flaws may be detected and corrected in situ. This streamlined in-process solution could ensure components are completed on time, while reducing production costs and ensuring a right-first-time product. Currently, inspection of narrow gap welds is notoriously difficult using traditional ultrasonic phased array methods, which must be addressed before an in-process system can be deployed. This difficulty arises from the vertical nature of Lack-of-Sidewall Fusion (LOSWF) defects in these weld geometries. This work introduces the dual-tandem phased array method, which utilises two phased array probes in a pitch-catch configuration allowing both pulse-echo and though-weld detection. Coupled with Full Matrix Capture (FMC) acquisition and Total Focusing Method (TFM) imaging, it has been shown that vertical notch defects can be detected with high Signal-to-Noise Ratio (SNR) using this method in a mock-narrow gap weld setup through the use of multi-mode and multi-view imaging. Additionally, it is shown that this method can be implemented for in-process weld geometries, allowing detection of vertical notch defects in the presence of partial weld geometric reflections. This is achieved through the implementation of adaptive delay law calculation, while imaging using both phase and amplitude based delay-and-sum imaging techniques. This work also proposes an adaptive probe adjustment technique for optimisation of array positioning during in-process inspection. Furthermore, a data compression technique utilising coded excitation has been developed and demonstrated, allowing single-bit digitisation of ultrasonic data. This has been shown to provide comparable results to standard resolution digitisation when implemented with TFM and Phase Coherence Imaging (PCI) of tip-diffraction from a notch defect, with limited SNR compromise. This has also been demonstrated at low transmit voltages, potentially paving the way for an intrinsically safe and lightweight imaging system. In addition, the ability to acquire single-bit data reduces transfer rates, image processing times and data storage requirements. The accumulation of this work is intended to provide a path towards the development of an in-process phased array inspection technique for narrow gap welds.
- Advisor / supervisor
- MacLeod, Charles
- Mohseni, Ehsan
- Resource Type
- DOI
- Funder
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PDF of thesis T17037 | 2024-08-13 | Public | Download |