Browsing by Author "Smith, MC"
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- ItemComprehensive numerical analysis of a three-pass bead-in-slot weld and its critical validation using neutron and synchrotron diffraction residual stress measurements(Pergamon-Elsevier Science LTD, 2012-05-01) Muránsky, O; Smith, MC; Bendeich, PJ; Holden, TM; Luzin, V; Martins, RV; Edwards, LThe current paper presents a finite element simulation of the residual stress field associated with a three pass slot weld in an AISI 316LN austenitic stainless steel plate. The simulation is split into uncoupled thermal and mechanical analyses which enable a computationally less expensive solution. A dedicated welding heat source modelling tool is employed to calibrate the ellipsoidal Gaussian volumetric heat source by making use of extensive thermocouple measurements and metallographic analyses made during and after welding. The mechanical analysis employs the Lemaitre-Chaboche mixed hardening model. This captures the cyclic mechanical response which a material undergoes during the thermo-mechanical cycles imposed by the welding process. A close examination of the material behaviour at various locations in the sample during the welding process, clearly demonstrates the importance of defining the correct hardening and high temperature softening behaviour. The simulation is validated by two independent diffraction techniques. The well-established neutron diffraction technique and a very novel spiral slit X-ray synchrotron technique were used to measure the residual stress-strain field associated with the three-pass weld. The comparison between the model and the experiment reveals close agreement with no adjustable parameters and clearly validates the used modelling procedure. Crown Copyright (C) 2011 Elsevier Ltd.
- ItemElectron 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, VFerritic 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
- ItemFull field measurement of plastic flow properties in a multi-pass austenitic stainless steel weld specimen.(American Society of Mechanical Engineers (ASME), 2008-07-27) Ganguly, S; Turski, M; Fitzpatrick, ME; Edwards, L; Smith, MC; Bouchard, PJKnowledge of constitutive material stress strain properties is important for reliable prediction of weld residual stress fields using analytical stress simulation techniques. The present work investigates the surface stress strain behaviour of a 3-pass groove-welded austenitic stainless steel disc. A relatively novel electronic speckled pattern interferometry (ESPI) technique was employed to monitor the surface deformation pattern across the weld, HAZ and parent metal of the specimens with very high spatial resolution. The deformation data was then analysed to determine the constitutive stress-strain property across the welded specimen. The analyses show very different patterns of proof stress variation across the pass I and pass III weld metal. The accumulated plastic strain in the pass I weld metal resulted in an increase of the 0.2% PS value by 175 MPa. © 2008 ASME
- ItemThe impact of axi-symmetric boundary conditions on predicted residual stress and shrinkage in a PWR nozzle dissimilar metal weld(American Society of Mechanical Engineers (ASME), 2012-07-15) Bendeich, PJ; Muránsky, O; Hamelin, CJ; Smith, MC; Edwards, LSimulation of a dissimilar metal weld (DMW) in a pressurised water reactor (PWR) nozzle was performed to predict both axial distortion and hoop residual stresses in the weld. For this work a computationally efficient axi-symmetric finite element (FE) simulation was carried out rather than a full 3D analysis. Due to the 2-dimensional nature of the analysis it was necessary to examine the effect of structural restraint during welding of the main dissimilar metal weld (DMW). Traditionally this type of analysis is set up to allow one end of the structure, in this case the safe-end forging, to be unrestrained in the axial direction during welding. In reality axial expansion and subsequent contraction of deposited weld metal at the current torch position is restrained by solidified material both ahead and behind the torch. Thus the conventional axi-symmetric analysis is under-restrained in the axial direction at least during the early weld passes. The significance of this was examined by repeating the current simulation with the safe-end forging fixed to limit expansion during the heat up cycle. Contraction was however, allowed during cooling cycle. This modified boundary control method provided a significantly improved prediction of the axial distortion across the weld as well as improved prediction of through wall axial and hoop residual stresses. Copyright © 2012 The American Society of Mechanical Engineers
- ItemNumerical analysis of retained residual stresses in C(T) specimen extracted from a multi-pass austenitic weld and their effect on crack growth(Elsevier, 2014-08) Muránsky, O; Smith, MC; Bendeich, PJ; Hosseinzadeh, F; Edwards, LSmall scale fracture mechanics test specimens of austenitic stainless steel weld and heat affected zone material are often extracted from non-heat-treated weldments, which contain significant weld residual stresses. Although these stresses are substantially relaxed by the process of specimen extraction, they may still reach levels that can affect subsequent testing if the applied loads are low and deformation is elastic. Long-term creep crack growth testing is one such case, where failure to take account of retained residual stresses could result in unrealistically high measurements of creep crack growth at applied load levels equivalent to those in operating plant. This paper describes a research programme to predict the start-of-creep-test levels of retained residual stress and residual stress intensity factor in compact tension C(T) specimen blanks extracted from non-post heat-treated AISI 316 weldments. The simulations were validated using neutron diffraction and slitting residual stress measurements and stress intensity factor measurement. A pass-by-pass finite element simulation of the original weldment is performed first, and followed by extraction of the C(T) specimen blank. The predicted retained residual stresses in the specimen are compared with residual stress measurements made on similar blank using neutron diffraction, and slitting techniques. The elastic stress intensity factor due to residual stress is then evaluated on the crack plane of the C(T) specimen and compared with experimental measurements made using the slitting method. Good agreement is achieved between measurement and simulation, providing validated basis for future modelling of long term creep crack growth tests. © 2014, Elsevier Ltd.
- ItemOn 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, PThe 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.
- ItemOptimisation of mixed hardening material constitutive models for weld residual stress simulation using the NeT task group 1 single bead on plate benchmark problem.(American Society of Mechanical Engineers (ASME), 2009-07-26) Smith, MC; Nadri, B; Smith, AC; Carr, DG; Bendeich, PJ; Edwards, LA single weld bead deposited on a flat plate is a deceptively simple problem that is in practice a challenge for both measurement and prediction of weld residual stresses. Task Group 1 of the NeT collaborative network has examined this problem in an extensive programme of measurement and simulation extending from 2002 to 2008. As a result, the NeT bead on plate forms an ideal benchmark problem for the development of weld residual stress simulation techniques. One of the conclusions of NeT Task Group 1 is that the most accurate predictions of weld residual stresses in austenitic steels are achieved using mixed isotropic-kinematic material constitutive models. However, the use of these models can require both extensive materials data, and compromises in fitting either the monotonic or cyclic responses. This paper reports a detailed matrix of sensitivity studies aimed at optimising the behaviour of mixed hardening models in welding simulation, using the Lemaitre-Chaboche formulation in the ABAQUS finite element code. Predicted stresses and strains in the NeT bead on plate specimen are compared with the extensive database of residual stress measurements. Further studies examine sensitivity to the handling of high temperature inelastic strains, using a novel two-stage annealing functionality implemented within ABAQUS. The results show that, overall, the most accurate predictions are made if the Lemaitre-Chaboche parameters are optimised to fit the monotonic response over the first 2% of plastic strain. However, further improvements in prediction could be achieved if the constitutive model were capable of independently fitting both the monotonic and saturated cyclic response of the material.
- ItemPrediction and measurement of weld residual stresses in thermally aged girth-welded austenitic steel pipes(American Society of Mechanical Engineers (ASME), 2012-07-15) Muránsky, O; Smith, MC; Bendeich, PJ; Hamelin, CJ; Edwards, LThe current paper describes finite element simulation of the complete manufacturing and service exposure history of girth-welded austenitic steel pipes fabricated from ESSHETE 1250 material for the STYLE Framework 7 project. The simulation campaign examines the impacts of prior quenching of pipe material, fabrication of closely adjacent welds, variation in mixed isotropic-kinematic hardening material constitutive models, and high temperature (650°C) service exposure (thermal ageing). The predicted residual stresses are validated using measurements made with the deep hole drilling (DHD) and incremental deep hole drilling (iDHD) techniques. Copyright © 2012 The American Society of Mechanical Engineers
- ItemA residual stress measurement and numerical analysis round robin on a three-pass slot nickel-base repair weld(Elsevier B. V., 2021) Arkivos, V; Smith, MC; Muránsky, O; Ohms, C; Youtsos, AGThe activities within a European network to develop accurate experimental and numerical methods to assess residual stresses (RS) in structural weldments are reported. The NeT Task Group 6 or 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 RS measurement and simulation round robins were performed. RS were measured using neutron diffraction at 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. TG6 gives a valuable insight into the real-world variability of diffraction-based RS measurements, and forms a reliable foundation against which to benchmark other measurement methods. The mean profile of measured RS was used to validate the accuracy achieved by the network on the prediction of RS. © 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
- ItemThe role of plasticity theory on the predicted residual stress field of weld structures(Materials Science Forum, 2014-11) Muránsky, O; Hamelin, CJ; Smith, MC; Bendeich, PJ; Edwards, LConstitutive plasticity theory is commonly applied to the numerical analysis of welds in one of three ways: using an isotropic hardening model, a kinematic hardening model, or a mixed isotropic-kinematic hardening model. The choice of model is not entirely dependent on its numerical accuracy, however, as a lack of empirical data will often necessitate the use of a specific approach. The present paper seeks to identify the accuracy of each formalism through direct comparison of the predicted and actual post-weld residual stress field developed in a three-pass 316LN stainless steel slot weldment. From these comparisons, it is clear that while the isotropic hardening model tends to noticeably over-predict and the kinematic hardening model slightly under-predict the residual post-weld stress field, the results using a mixed hardening model are quantitatively accurate. Even though the kinematic hardening model generally provides more accurate results when compared to an isotropic hardening formalism, the latter might be a more appealing choice to engineers requiring a conservative design regarding weld residual stress. © 2014, Trans Tech Publications.
- ItemSensitivity of predicted weld residual stresses in the NeT task group 1 single bead on plate benchmark problem to finite element mesh design and heat source characteristics(American Society of Mechanical Engineers (ASME), 2009-07-26) Bendeich, PJ; Smith, MC; Carr, DG; Edwards, LA single weld bead deposited on a flat plate is a deceptively simple problem that is, in practice, a significant challenge for both measurement and prediction of weld residual stresses. Task Group 1 of the NeT collaborative network has examined this problem in an extensive programme of measurement and simulation extending from 2002 to 2008. Thus, the NeT bead on plate forms an ideal benchmark problem for the development of weld residual stress simulation techniques. It is often difficult to separate the influence of different analysis variables in a large collaborative study such as NeT Task Group 1. This paper examines sensitivity to mesh design, element type, and heat source characteristics in a closely controlled study using several different mesh designs, element types (both tetrahedral and hexahedral), and heat sources, but the same material constitutive model and finite element analysis code. It complements a companion paper that varies material constitutive models. A dedicated heat source modelling tool with a semi-automatic interface to the ABAQUS finite element code has been used to vary the heat source characteristics, thus facilitating rapid and controlled sensitivity studies without the need for bespoke heat source coding within ABAQUS.
- ItemSpatially resolved materials property data from a uniaxial cross-weld tensile test(American Society of Mechanical Engineers (ASME), 2009-12) Turski, M; Smith, MC; Bouchard, PJ; Edwards, L; Withers, PJApplication of electronic speckle pattern interferometry (ESPI) is described to measure the spatial variation in monotonic tensile stress-strain properties along “cross-weld” specimens machined from a stainless steel three-pass welded plate. The technique, which could also be done with digital image correlation, was applied to quantify how the material 0.2%, 1%, 2%, 5%, 10%, and 20% proof stress varied with distance from the center-line of the weldment for parent and weld material associated with the first and final passes. The stress-strain curves measured by the ESPI method correlated closely with stress-strain data measured using conventional test specimens. The measured results are consistent with the hypothesis that thermo-mechanical cycles associated with the welding process work harden previously deposited (single-pass) weld metal and the surrounding parent material. The stress-strain response of the heat affected zone adjacent to the first weld pass is consistent with an accumulated (equivalent monotonic) plastic strain of 6.5% and that of the first pass weld bead was consistent with an accumulated plastic strain of approximately 4% greater than the state of the final pass weld metal. © 2009, American Society of Mechanical Engineers (ASME)
- ItemUsing advaced weld modelling to ensure the structural integrity of plant in the nuclear industry(Australian Nuclear Association, 2011-10-07) Muránsky, O; Bendeich, PJ; Smith, MC; Edwards, LNot available. Physical copy available in ANSTO Library at 621.48/17
- ItemValidation of a numerical model used to predict phase distribution and residual stress in ferritic steel weldments(Elsevier, 2014-08-15) Hamelin, CJ; Muránsky, O; Smith, MC; Holden, TM; Luzin, V; Bendeich, PJ; Edwards, LNumerical finite element analyses were combined with experimental observation of a single-pass autogenous beam weld in SA508 Gr.3 Cl.1 ferritic steel. Two weldment sets were prepared using different weld heat inputs, resulting in different post-weld residual stress and ferritic phase distributions. Neutron diffraction was employed to measure the residual stress distribution while microhardness measurements were used to measure the post-weld phase distribution in each weldment. In both cases, the numerical model accurately predicts the ferritic phase distribution and residual stress field. Model predictions illustrate how the higher cooling rates associated with a faster torch speed result in an increased martensite volume fraction within the weldment. Consideration of both the transformation kinetics and transformation plasticity are proven to significantly improve model accuracy when comparing measured and predicted residual stress profiles. © 2014, Acta Materialia Inc.