Browsing by Author "Smith, Mike"

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    Assessing and mitigating the distortion and stress during electron beam welding of a large shell-flange structure
    (Elsevier, 2022-08-30) Sun, Yongle; Smith, Mike; Dutilleul, Thomas; Jones, Steve
    Electron beam (EB) welding can efficiently join large-scale components using one single autogenous pass, but it still faces challenges associated with weld-induced distortion and stress. This study investigates EB welding in a low-alloy steel thick-section shell-flange structure for a small modular reactor. A 3D thermal-metallurgical-mechanical model is developed to assess the weld-induced distortion and stress, as well as the strategy to mitigate them. When no restraint is imposed on the circumferential weld plane, an opening and sliding gap develops during the EB welding, which can cause weld defects and even process failure. Restraint through tack welds can effectively mitigate the gapping distortion, but it generates high transient tensile stress in the tack weld. Circumferentially continuous tack weld is preferential over circumferentially discrete tack welds to minimise the tensile stress. The final residual stress is insensitive to the tack-weld restraint, and the stress distribution in the steady-state welding region is broadly similar to that found in plate butt welds. However, concentration of residual stresses with high triaxiality occurs in the weld stop region, with high tensile stresses generated just behind the beam stop location, which cannot be diminished by overlap welding or change of weld stop position. The mechanisms responsible for the distortion and the transient and residual stresses are analysed. This study could provide rational basis for designing weld restraint to control distortion and guiding stress mitigation strategy for crack-susceptible region in EB weldments.
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    Data supporting: 'Assessing and mitigating the distortion and stress during electron beam welding of a large shell-flange structure'
    (Cranfield University, 2022-08-31 15:56) Sun, Yongle; Smith, Mike; Dutilleul, Thomas; Jones, Steve
    Fig. 7. (c) temperature histories on the outer surface points (i.e., Out1 and Out2) and inner surface points (i.e., In1 and In2). Fig. 8. (d) The cross-weld line profile of hardness distribution. Fig. l10. Evolution of the opening (a) and sliding (b) displacements for mid-thickness ocations on the weld plane with different angular distances to the EB weld start position.
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    Towards the coordinated and fit-for-purpose deployment of Unmanned Aerial Systems (UASs) for flood risk management in England
    (IWA Publishing, 2022-07-18) Giannitsopoulos, Michail L.; Leinster, Paul; Butler, David; Smith, Mike; Rivas Casado, Monica
    Preparedness for flood emergency response is crucial for effective flood management. The need for advanced flood decision support tools that aid flood management has been recognized by several authors. This work examines the variability that currently exists across England with regard to the Unmanned Aerial System (UAS) data collection and processing strategy in flood emergency events. Expert elicitation was carried out using a tailored questionnaire about UAS deployment in three flood emergency scenarios. The survey highlighted that reduced equipment assembly time, a national network of appropriately qualified UAS pilots and the effective UAS deployment when on-site, can reduce the response time to flood emergency. For improved comparability and reduced bias in data collection and interpretation, clear guidelines on which data products are most beneficial for particular purposes, processing time required, platform and sensor selection may also be necessary. We consider that releasing a comprehensive documentation pack, which includes guidelines, standards and protocols that detail the methods, tools, technology, quantity and quality of data, to UAS pilots on a flood emergency call, will enhance the timely response.