Browsing by Author "Edwards, L"

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    Advanced nuclear reactor materials research in Australia: high temperature properties, radiation effects and corrosion behaviour
    (IAEA, 2020-05) Muránsky, O; Edwards, L
    The Australian Nuclear Science and Technology Organisation (ANSTO) and its predecessor, the Australian Atomic Energy Commission has a long history in nuclear-based research and development. This is continuing through Australia’s recent membership of the Generation IV International Forum (GIF). As Australia’s implementing agent within GIF, ANSTO is focussing the majority of its research on nuclear materials engineering including structural performance evaluations in complex nuclear environments, advanced manufacturing, and system reliability assessment. Although this work concentrates on the Molten Salt Reactor (MSR) and Very High Temperature Reactor (VHTR) systems most of the research outcomes are applicable to a wide range of advanced nuclear reactor systems.
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    Application of a soil model in the numerical analysis of landmine interaction with protective structures
    (DEStech Publications, 2011) Saleh, M; Edwards, L
    Blast analysis using numerical techniques has become increasingly relevant to anticipate the material response of protective structures. Improvised explosive devices and land mines pose a significant threat to the occupants of armoured vehicles, it’s therefore important to increase the accuracy of the numerical analysis by incorporating more sophisticated material models whilst maintaining mathematical tractability. The current research employs an Arbitrary Lagrangian Eulerian (ALE) numerical technique in the hydrocode LS-DYNA for the analysis of the blast event. Further, incorporation of a soil model was carried out for the analysis of a TNT mine blast on a mild steel plate. The primary goals of the research are the implementation of an appropriate soil model and the use of multi-physics finite element analysis to model fluid structure interaction. The agreement with experimental result is very good and the methodology employed captured some important aspects of the blast-structure interaction.
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    Application of the work of indentation approach for the characterization of aluminium 2024-T351 and Al cladding by nanoindentation
    (Springer, 2009-02) Khan, MK; Hainsworth, SV; Fitzpatrick, ME; Edwards, L
    Nanoindentation has been used to characterize the mechanical properties of aerospace-grade Al2024-T351 with and without a clad layer of pure aluminium. The clad layer is introduced by means of a roll-bonding process which can cause significant work-hardening of the material in the clad layer. The hardness and Young’s modulus of the pure aluminium and the Al2024 have been determined by a number of methods, including the traditional Oliver and Pharr method, and a number of other methods, including direct measurement of the indentation by atomic force microscopy, and evaluation of the work of indentation. The Oliver and Pharr method was found to underestimate the area of contact as it did not include the area of piled-up material around the indentation periphery. This gave a corresponding overestimation of both hardness and modulus. The area of the indentation measured by atomic force microscopy was similarly found to underestimate the contact area owing to relaxation of material around the indent between indentation and imaging. The work of indentation approach was found to give good agreement between the hardness calculated by nanoindentation and those found in the literature. © 2009, Springer.
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    Australia’s participation in the Generation IV International Forum (GIF)
    (Australian Nuclear Science and Technology Organisation, 2017-10-06) Edwards, L
    On 14 September 2017, Australia deposited its instrument of accession to the Generation IV International Forum (GIF) Framework Agreement for International Collaboration on Research and Development of Generation IV Nuclear Energy Systems with the GIF secretariat at the OECD. The GIF is a co-operative international endeavour, which was established to carry out the research and development needed to establish the feasibility and performance capabilities of the next generation of nuclear energy systems. Australia became the 14th member of the GIF on 22 June 2016 when it signed the GIF Charter. Acceding to the Framework Agreement enables Australia to become actively engaged in R&D projects related to Generation IV 2 ANA2017 Conference, Sydney, NSW, 6 Oct 2017 systems, particularly in R&D projects on advanced materials. The story of Australia’s engagement with GIF will be described and the scope and nature of its contributions to future GIF R&D including which of the six GIF Advanced Reactor systems Australia will support will be described together with the role of ANSTO as Australia’s implementing agent within GIF.
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    Ballistic performance of multi-layered metallic plates impacted by a 7.62-mm APM2 projectile
    (Elsevier, 2011-12-01) Flores-Johnson, EA; Saleh, M; Edwards, L
    This paper presents a numerical investigation of the ballistic performance of monolithic, double- and triple-layered metallic plates made of either steel or aluminium or a combination of these materials, impacted by a 7.62-mm APM2 projectile in the velocity range of 775-950 m/s. Numerical models were developed using the explicit finite element code LS-DYNA. It was found that monolithic plates have a better ballistic performance than that of multi-layered plates made of the same material. This effect diminishes with impact velocity. It was also found that double-layered plates with a thin front plate of aluminium and thick back steel plate exhibit greater resistance than multi-layered steel plates with similar areal density. These predictions indicate that multi-layered targets using different metallic materials should be investigated for improved ballistic performance and weight-savings. Crown Copyright (C) 2011 Published by Elsevier Ltd.
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    Characterization of complex carbide–silicide precipitates in a Ni–Cr–Mo–Fe–Si alloy modified by welding
    (Elsevier B.V., 2015-07-01) Bhattacharyya, D; Davis, J; Drew, M; Harrison, RP; Edwards, L
    Nickel based alloys of the type Hastelloy-N™ are ideal candidate materials for molten salt reactors, as well as for applications such as pressure vessels, due to their excellent resistance to creep, oxidation and corrosion. In this work, the authors have attempted to understand the effects of welding on the morphology, chemistry and crystal structure of the precipitates in the heat affected zone (HAZ) and the weld zone of a Ni–Cr–Mo–Fe–Si alloy similar to Hastelloy-N™ in composition, by using characterization techniques such as scanning and transmission electron microscopy. Two plates of a Ni–Cr–Mo–Fe–Si alloy GH-3535 were welded together using a TiG welding process without filler material to achieve a joint with a curved molten zone with dendritic structure. It is evident that the primary precipitates have melted in the HAZ and re-solidified in a eutectic-like morphology, with a chemistry and crystal structure only slightly different from the pre-existing precipitates, while the surrounding matrix grains remained unmelted, except for the zones immediately adjacent to the precipitates. In the molten zone, the primary precipitates were fully melted and dissolved in the matrix, and there was enrichment of Mo and Si in the dendrite boundaries after solidification, and re-precipitation of the complex carbides/silicides at some grain boundaries and triple points. The nature of the precipitates in the molten zone varied according to the local chemical composition. © 2015 Elsevier Inc.
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    Characterization of complex carbide–silicide precipitates in a Ni–Cr–Mo–Fe–Si alloy modified by welding
    (Materials Australian and The Australian Ceramic Society, 2015-02-09) Bhattacharyya, D; Davis, J; Drew, M; Harrison, RP; Edwards, L
    Nickel based alloys of the type Hastelloy-N™ are ideal candidate materials for molten salt reactors, as well as for applications such as pressure vessels, due to their excellent resistance to creep, oxidation and corrosion. In this work, the authors have attempted to understand the effects of welding on the morphology, chemistry and crystal structure of the precipitates in the heat affected zone (HAZ) and the weld zone of a Ni–Cr–Mo–Fe–Si alloy similar to Hastelloy-N™ in composition, by using characterization techniques such as scanning and transmission electron microscopy. Two plates of a Ni–Cr–Mo–Fe–Si alloy GH-3535 were welded together using a TiG welding process without filler material to achieve a joint with a curved molten zone with dendritic structure. It is evident that the primary precipitates have melted in the HAZ and re-solidified in a eutectic-like morphology, with a chemistry and crystal structure only slightly different from the pre-existing precipitates, while the surrounding matrix grains remained unmelted, except for the zones immediately adjacent to the precipitates. In the molten zone, the primary precipitates were fully melted and dissolved in the matrix, and there was enrichment of Mo and Si in the dendrite boundaries after solidification, and re-precipitation of the complex carbides/silicides at some grain boundaries and triple points. The nature of the precipitates in the molten zone varied according to the local chemical composition. - Graphical abstract: Display Omitted - Highlights: • Ni-based alloy with Cr, Mo, Si, Fe and C was welded, examined with SEM, EBSD, and TEM. • Original Ni{sub 2}(Mo,Cr){sub 4}(Si,C) carbides changed from equiaxed to lamellar shape in HAZ. • Composition and crystal structure remained almost unchanged in HAZ. • Original carbides changed to lamellar Ni{sub 3}(Mo,Cr){sub 3}(Si,C) in some cases in weld metal. • Precipitates were mostly incoherent, but semi-coherent in some cases in weld metal.
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    Colloidal processing of zirconium diboride ultra-high temperature ceramics
    (John Wiley and Sons, 2013-05-21) Tallon, C; Chavara, DT; Gillen, AL; Riley, D; Edwards, L; Moricca, SA; Franks, GV
    Colloidal processing of the Ultra-High Temperature Ceramic (UHTC) zirconium diboride (ZrB2) to develop near−net-shaping techniques has been investigated. The use of the colloidal processing technique produces higher particle packing that ultimately enables achieving greater densification at lower temperatures and pressures, even pressureless sintering. ZrB2 suspension formulations have been optimized in terms of rheological behavior. Suspensions were shaped into green bodies (63% relative density) using slip casting. The densification was carried out at 1900°C, 2000°C, and 2100°C, using both hot pressing at 40 MPa and pressureless sintering. The colloidally processed materials were compared with materials prepared by a conventional dry processing route (cold pressed at 50 MPa) and subjected to the same densification procedures. Sintered densities for samples produced by the colloidal route are higher than produced by the dry route (up to 99.5% relative density by hot pressing), even when pressureless sintering is performed (more than 90% relative density). The promising results are considered as a starting point for the fabrication of complex-shaped components that can be densified at lower sintering temperatures without pressure. © 2013, The American Ceramic Society.
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    Combined experimental and finite element approach for determining mechanical properties of aluminium alloys by nanoindentation.
    (Elsevier, 2010-10) Khan, MK; Hainsworth, SV; Fitzpatrick, ME; Edwards, L
    Aluminium alloys for the aerospace industry are often clad by roll-bonded aluminium to improve corrosion resistance. The clad layer is of the order of 100 μm in thickness and it is difficult to determine the mechanical properties of this layer by conventional mechanical testing techniques. Nanoindentation is ideally suited to determining the elastic and plastic properties of such layers and here we report on a combined approach using experimental nanoindentation and finite element analysis to extract yield stress and strain hardening exponent for an Al-clad system. The approach used was calibrated against results for an Al 2024-T351 alloy, where conventional mechanical testing data was available. For the Al 2024-T351, a forward analysis was used for extraction of load–displacement curves at different indentation depths with the help of elastic–plastic properties obtained from tensile testing. For a 100 μm clad layer of pure aluminium on Al 2024-T351, reverse analysis was used for extraction of elastic–plastic properties from a single indentation test. A yield stress of 110–120 MPa and a value of 0.075–0.1 for the work hardening exponent was obtained for the Al cladding. Nanoindentation properties including maximum load of indentation, contact depth, area of contact and pile-up obtained from the forward and reverse analyses showed excellent agreement with the experimental results. © 2010, Elsevier Ltd.
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    A comparison of microstructural strengthening for thermal creep and radiation damage resistance of titanium aluminide alloys
    (Elsevier, 2013-07-01) Zhu, HL; Wei, T; Carr, DG; Harrison, RP; Edwards, L; Seo, DY; Maruyama, K
    Titanium aluminide (TiAl) alloys were initially developed for moderate temperature (600–850 °C) applications in the aerospace and automotive industries because they have high specific strength, low density, good corrosion, oxidation and creep resistance at elevated temperatures [1]. TiAl alloys have also received much attention as potential candidate materials for high temperature nuclear structural applications because of excellent radiation resistance and low neutron activation [2], [3], [4] and [5]. Moreover, the microstructure of TiAl alloys can be developed to be more complex than the up-to-now reported microstructures of other advanced structural materials. Various microstructures allow different combinations of properties for various extreme environments in advanced nuclear systems. The effects of microstructural features on creep behaviour of TiAl alloys have been intensively investigated over the last two decades [6], [7] and [8]. However, the effects of microstructural features on irradiation behaviour of TiAl alloys have rarely been studied. In the present short note, the microstructural strengthening for thermal creep and irradiation damage of TiAl alloys is compared. This provides useful guidance for further experiment work necessary to understand the irradiation behaviour of TiAl alloys. © 2013, Elsevier B.V.
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    Comprehensive 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, L
    The 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.
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    Determination of the residual stress field around scratches using synchrotron x-rays and nanoindentation.
    (Trans Tech Publications, 2009-11-10) Khan, MK; Fitzpatrick, ME; Edwards, L; Hainsworth, SV
    The residual strain field around the scratches of 125µm depth and 5µm root radius have been measured from the Synchrotron X-ray diffraction. Scratches were produced using different tools in fine-grained aluminium alloy AA 5091. Residual stresses up to +1700 micro-strains were measured at the scratch tip for one tool but remained up to only +1000 micro-strains for the other tool scratch. The load-displacement curves obtained from nanoindentation were used to determine the residual stresses around the scratches. It was found that the load-displacement curves are sensitive to any local residual stress field present and behave according to the type of residual stresses. This combination of nanoindentation and synchrotron X-rays has been proved highly effective for the study of small-scale residual stresses around the features such as scratches. © 2020 by Trans Tech Publications Ltd.
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    Effect of double ion implantation and irradiation by Ar and He ions on nano-indentation hardness of metallic alloys
    (Elsevier, 2013-07-01) Dayal, P; Bhattacharyya, D; Mook, WM; Fu, EG; Wang, YQ; Carr, DG; Anderogluc, O; Mara, NA; Misra, A; Harrison, RP; Edwards, L
    In this study, the authors have investigated the combined effect of a double layer of implantation on four different metallic alloys, ODS steel MA957, Zircaloy-4, Ti–6Al–4V titanium alloy and stainless steel 316, by ions of two different species – He and Ar – on the hardening of the surface as measured by nano-indentation. The data was collected for a large number of indentations using the Continuous Stiffness Method or “CSM” mode, applying the indents on the implanted surface. Careful analysis of the data in the present investigations show that the relative hardening due to individual implantation layers can be used to obtain an estimate of the relative hardening effect of a combination of two separate implanted layers of two different species. This combined hardness was found to lie between the square root of the sum of the squares of individual hardening effects, (ΔHA2 + ΔHB2)0.5 as the lower limit and the sum of the individual hardening effects, (ΔHA + ΔHB) as the upper limit, within errors, for all depths measured.© 2013, Elsevier B.V.
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    Effect of frequency on high-temperature fatigue crack growth in a silicon carbide reinforced silicon nitride composite
    (Elsevier, 2013-02-01) Moffatt, JE; Fitzpatrick, ME; Edwards, L
    A detailed study on a silicon nitride reinforced with silicon carbide whiskers, Si3N4SiCW, has been undertaken at elevated temperature during static and dynamic loading at increasing K and ΔK respectively. It is shown that cyclic sub-critical crack growth rates are lower than static crack growth rates. The increased crack growth rate during static far field loading is attributed to the stress relaxation of the inter-granular glass phase which allows time-dependent processes to occur ahead of the crack tip which lead to enhanced sub-critical crack growth rates. During cyclic fatigue the glass phase has insufficient time to relax and glassy ligaments are able to bridge the crack wake thereby shielding the crack tip from the full force of the applied load. Also, at particular temperatures, bridging between the surfaces of the crack wake by the inter-granular glass phase results in increased strength and fatigue retardation. The extent of ‘crack wake healing’ is shown to be time and temperature dependent. The viscosity of the glass phase is directly related to the temperature and the bonding force associated with glass phase bridging is observed to reduce with increasing temperature. The results from a previous study at room temperature are compared to those found during this investigation. © 2012, Elsevier Ltd.
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    Effect of tool profile and fatigue loading on the local hardness around scratches in clad and unclad aluminium alloy 2024.
    (Elsevier, 2009-12-15) Khan, MK; Fitzpatrick, ME; Hainsworth, SV; Edwards, L
    Nanoindentation has been used to study the hardness changes produced by scratching of aluminium alloy AA2024, with and without a clad layer of pure aluminium. The hardness was mapped around scratches made with diamond tools of different profiles. One tool produced significant plastic damage with associated hardening at the scratch root, whilst the other produced a ‘cleaner’ cut with no hardening. The different behaviours are attributed to whether the tool makes the scratch by a ‘cutting’ or a ‘ploughing’ mechanism. The degree of plastic damage around the scratches has been correlated with peak broadening data obtained using synchrotron X-ray diffraction. There was no change observed in the local hardness around the scratch with fatigue loading. © 2009, Elsevier Ltd.
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    Effect of weld residual stresses and their re-distribution with crack growth during fatigue under constant amplitude loading
    (Elsevier, 2010-04) Liljedahl, CDM; Zanellato, O; Fitzpatrick, ME; Lin, J; Edwards, L
    In this work the evolution of the residual stresses in a MIG-welded 2024-T3 aluminium alloy M(T) specimen during in situ fatigue crack growth at constant load amplitude has been measured with neutron diffraction. The plastic relaxation and plasticity-induced residual stresses associated with the fatigue loading were found to be small compared with the stresses arising due to elastic re-distribution of the initial residual stress field. The elastic re-distribution was modelled with a finite element simulation and a good correlation between the experimentally-determined and the modelled stresses was found. A significant mean stress effect on the fatigue crack growth rate was seen and this was also accurately predicted using the measured initial residual stresses. © 2010, Elsevier Ltd.
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    European Network on Neutron Techniques Standardization for Structural Integrity - NeT.
    (American Society of Mechanical Engineers (ASME), 2008-07-27) Ohms, C; Martins, RV; Uca, O; Youtsos, AG; Bouchard, PJ; Smith, M; Keavey, M; Bate, SK; Gilles, P; Wimpory, RC; Edwards, L
    This paper provides an overview over the work of the European Network on Neutron Techniques Standardization for Structural Integrity (NeT). The network involves some 35 organisations from industry and academia and these partners undertake the application of modern experimental and numerical techniques to problems related to the structural integrity of components, mainly relevant to nuclear applications. While being built around neutron scattering techniques, which are predominantly applied for analyses of welding residual stresses, one of the major strengths of the consortium is the diversity in available experimental and numerical techniques. In the residual stress area, for example, many types of materials characterizations testing, several methods for residual stress analysis, including neutron and X-ray diffraction, deep hole drilling, the contour method and others, and many different ways of numerical analysis employing several commercially available FEM codes can be covered by the partners. Currently the network has embarked on five different Task Groups. Four of these are dealing with welding residual stress assessment, and one applies Small Angle Neutron Scattering for studying thermal ageing processes in duplex stainless steels used for reactor core internals. The work already performed in the context of NeT and the envisaged investigations for the ongoing Task Groups are briefly outlined in this paper. The aim is to give the reader a comprehensive overview of the work of NeT and to shed some light on the potential present in this kind of collaborative effort. © The American Society of Mechanical Engineers
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    Evaluation of a hydrocode in modelling NATO threats against steel armour
    (International Symposium on Ballistics, 2010-01-01) Saleh, M; Edwards, L
    Having identified relevant constitutive models and the likely fracture mechanisms, a benchmarking study was undertaken to numerically compute a perforation solution based on the work by Børvik et al [1]. Material strength of ductile metals subjected to high strain phenomena is often described through the Johnson-Cook model [2] or the Zerilli-Armstrong [3] relation; both describe strain rate sensitivity, strain hardening and thermal softening albeit by different means. Phenomenological models like Johnson and Cook’s [2] and the associated fracture criterion by the same authors [4] have been extensively used [1,5-8] across a number of research areas. Whilst useful in capturing the main deformation and failure mechanisms, the author’s note the inherent deficiencies present in these models and resolve to calculating conservative solutions. The study also evaluates the blast response of an elasto-plastic plate using the commercial FEA code LS-DYNA[10]. The peak displacement of each plate is compared to literature [11] through two blast analysis techniques, namely the CONWEP blast code which is embedded in the hydrocode and the computationally expensive, but more accurate, technique of fluid structure coupling via a multi-material ALE formulation. The blast threat is a 6 kg TNT mine modelled using the steel pot test criteria set out by the NATO standard in AEP-55 Vol.2. The ALE formulation is competently described in [12] and we apply it to validate wether it’s applicable for near field blast analysis. We aim to shed some light on the nuances and the problems associated with modelling highly dynamic problems. In the words of Jean Lemaitre and Rodrigue Desmorat [14]: “Very accurate calculations are too often made with a very poor accuracy of the material parameters”
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    Evaluation of residual stresses in electron-beam welded Zr2.5Nb0.9Hf Zircadyne flange mock-up of a reflector vessel beam tube flange
    (Elsevier Science BV., 2013-07-01) Muránsky, O; Holden, TM; Kirstein, O; James, JA; Paradowska, AM; Edwards, L
    The dual-phase alloy Zr2.5Nb alloy is an important nuclear material, because of its use in current and possible use in future nuclear reactors. It is, however, well-known that Zr2.5Nb weldments can fail through a time-dependent mechanism called delayed hydride cracking which is typically driven by the presence of tensile residual stresses. With a view to understanding the development of residual stresses associated with Zr2.5Nb welds the current study focuses on the evaluation of the residual stresses in a mock-up of a reactor beam tube flange made from Zr2.5Nb0.9Hf. The present results suggests that, like ferritic welds which undergo a solid-state phase transformation upon welding, Zr2.5Nb0.9Hf welds also develop high tensile residual stresses in the heat-affected zone whereas the stresses closer to the weld tip are reduced by the effects of the beta -> alpha solid-state phase transformation. © 2013, Elsevier Ltd.
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    Evaluation of soil and fluid structure interaction in blast modelling of the flying plate test
    (Elsevier, 2015-04-15) Saleh, M; Edwards, L
    The influence of the soil properties on the structural integrity of impacted structures is important in light of the increased use of improvised explosive devices (IED’s) and buried explosives. The study deduces material parameters for the Federal Highway Authority (FHWA) soil model in LS-DYNA and comparisons are made with the ConWep and two commonly used soil models. The softening behaviour of semi-cohesive prairie soils due to pore pressure development and the reduction of the cohesion angle are highlighted. The flying plate test is used for validation with very good agreement found, capturing the plate’s kinematic and structural responses. © 2015, Elsevier Ltd.