Browsing by Author "Akrivos, V"

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    Electron beam weld modelling of ferritic steel: effect of prior-austenite grain size on transformation kinetics
    (Elsevier B. V., 2020-11-19) Vasileiou, AN; Hamelin, CJ; Smith, MC; Francis, JA; Sun, YL; Flint, TF; Xiong, Q; Akrivos, V
    Ferritic steels experience solid-state phase transformation (SSPT), which causes volumetric changes due to differences in the atomic packing density of different phases in the steel. The importance of the prior austenite grain size (PAGS) as an input physical variable is assessed, for adequately modelling the anisothermal SSPT during welding of ferritic steels. The knowledge of the PAGS value pre-requires a thorough microstructural study of each particular weld, information that might be difficult to acquire. A relationship between hardness, PAGS and phase fractions is proposed to be used to feed in weld models. The case of a single-pass, autogenous, reduced-pressure electron beam weld is used for this study. The adequacy of the finite-element weld model in predicting the micro-constituents, the hardness and the residual stress is demonstrated via comparing the predicted results of the thermo-metallurgical and stress analyses with the set of corresponding experimental data. This work aims at providing a better understanding of the impact of PAGS on transformation kinetics and best practice guidelines for modelling, using an extensively validated electron beam weld model as baseline. © 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
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    On the accurate prediction of residual stress in a three-pass slot nickel-base repair weld by numerical simulations
    (MDPI, 2022-06-01) Akrivos, V; Muránsky, O; Depradeux, L; Smith, MC; Vasileiou, A; Deaconu, V; Kapadia, P
    The activities within a European network to develop accurate experimental and numerical methods to assess residual stresses in structural weldments are reported. The NeT Task Group 6 or NeT-TG6 project examined an Alloy 600 plate containing a three-pass slot weld made with Alloy 82 consumables. A number of identical specimens were fabricated and detailed records of the manufacturing history were kept. Parallel measurement and simulation round robins were performed. Residual stresses were measured using neutron diffraction via five different instruments. The acquired database is large enough to generate reliable mean profiles, to identify clear outliers, and to establish the systematic uncertainty associated with this non-destructive technique. NeT-TG6 gives a valuable insight into the real-world variability of diffraction-based residual stress measurements, and forms a reliable foundation against which to benchmark other measurement methods. The mean measured profiles were used to validate the accuracy achieved by the network in the prediction of residual stresses. © 2022 The Authors.