Browsing by Author "Hoye, N"

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    Assessment of residual stress, hardness, and defect tolerance in a tee joint, as-welded and after post-weld heat treatment
    (Scientific Surveys Ltd, 2017-03-01) Law, M; Paradowska, AM; Hoye, N; Grace, P
    The risk of hydrogen-assisted cold cracking (HACC) is often conflated with the risk of brittle fracture. However, if delayed non-destructive testing (NDT) shows there are no defects, or defects below the critical crack size, then brittle fracture is not possible. Post-weld heat treatment (PWHT) is known to reduce the risk of HACC but is not always possible to perform. To assess the effects of PWHT, the residual stresses and hardness values were measured before and after PWHT to assess the effects of PWHT on HACC susceptibility and on the critical defect sizes. The residual stresses were lower than code-based estimates. PWHT reduced the residual stress and hardness, and increased the critical crack size. Copyright Scientific Surveys Ltd
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    Experimental investigation of welding stresses in MWIC weldability test
    (Materials Research Forum LLC, 2016-07-03) Alipooramirabad, H; Paradowska, AM; Ghomashchi, R; Hoye, N; Reid, M
    The use of high-strength steels in the manufacture of energy pipelines, coupled with the transition to larger pipe diameters and greater wall thicknesses, has led to an increased potential for cracking including hydrogen assisted cracking of energy pipelines due to higher constraint induced stresses. In the present study, a modified version of the Welding Institute of Canada (MWIC) restraint test was used to simulate the constraint conditions of full-scale girth welds on energy pipelines, allowing the influence of welding process parameters on crack formation to be assessed. MWIC test samples of X70 grade high-strength low alloy pipeline steel were manually welded using two different welding processes, namely shielded metal arc welding (SMAW) and modified short-arc welding (MSAW). Residual strains, and hence stresses, in these samples were analysed quantitatively using neutron diffraction technique. Overall, results indicate that the modified WIC restraint test produces significant residual stresses and so is effective in constraining the root run and in consequence studying the hydrogen assisted cracking of high-strength pipeline steels. © The Authors
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    Investigation of residual stresses in titanium aerospace components formed via additive manufacturing
    (Engineers Australia, 2014-01-01) Hoye, N; Li, HJ; Cuiuri, D; Paradowska, AM; Thorogood, KJ
    In the present study gas tungsten arc welding (GTAW) with automated wire addition was used to additively manufacture (AM) a representative thin-walled aerospace component from Ti-6Al-4V in a layer-wise manner. Residual strains, and hence stresses, were analysed quantitatively using neutron diffraction techniques on the KOWARI strain scanner at the OPAL research facility operated by the Australian Nuclear Science and Technology Organisation (ANSTO). Results showed that residual strains within such an AM sample could be measured with relative ease using the neutron diffraction method. Residual stress levels were found to be greatest in the longitudinal direction and concentrated at the interface between the base plate and deposited wall. Difficulties in measurement of lattice strains in some discrete locations within the deposited material were ascribed to the formation of localised grain orientation where α-Ti laths form in aligned colonies within prior β-Ti grain boundaries upon cooling. Neutron diffraction measurements of residual stress were cross-correlated using the contour method with results found to be in close agreement. Observations of microstructure reveal 'basket-weave' morphology typical of fusion welds in Ti-6Al-4V. Microhardness measurements show lower hardness in the deposited material compared to the base plate and a further small decrease in hardness in the top region of the deposit, indicating a dependence on thermal cycling from sequential weld deposition. © 2021 Informit
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    Measurement of residual stresses in titanium aerospace components formed via additive manufacturing
    (Trans Tech Publications Ltd, 2014-02) Hoye, N; Li, HJ; Cuiuri, D; Paradowska, AM
    In the present study gas tungsten arc welding (GTAW) with automated wire addition was used to additively manufacture (AM) a representative thin-walled aerospace component from Ti-6Al-4V in a layer-wise manner. Residual strains, and hence stresses, were analysed quantitatively using neutron diffraction techniques on the KOWARI strain scanner at the OPAL research facility operated by the Australian Nuclear Science and Technology Organisation (ANSTO). Results showed that residual strains within such an AM sample could be measured with relative ease using the neutron diffraction method. Residual stress levels were found to be greatest in the longitudinal direction and concentrated at the interface between the base plate and deposited wall. Difficulties in measurement of lattice strains in some discrete locations were ascribed to the formation of the formation of localised texturing where α-Ti laths form in aligned colonies within prior β-Ti grain boundaries upon cooling. Observations of microstructure reveal basket-weave morphology typical of welds in Ti-6Al-4V. Microhardness measurements show a drop in hardness in the top region of the deposit, indicating a dependence on thermal cycling from sequential welds. © 2014, Trans Tech Publications.
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    Neutron optics upgrades to the residual stress diffractometer, KOWARI
    (Materials Research Forum LLC, 2016-07-03) Reid, M; Olsen, SR; Luzin, V; New, M; Booth, N; Clowes, D; Nguyen, T; Franceschini, F; Ogrin, A; Pangelis, S; Paradowska, AM; Larkin, N; Pan, Z; Hoye, N; Suzuki, H
    In the last 5 years a number of significant enhancements have been implemented on the neutron beam strain scanner Kowari at the OPAL reactor in Sydney Australia. These changes have resulted in reduced beam time losses when conducting experiments due to sample and stage alignment, and optics and sample changes. There have been 3 projects, starting in 2011 with a new manual slit system design and collision recovery system, in 2013 with a series of radial collimators and finally with the delivery. © The Authors
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    Prediction of welding stresses in WIC test and its application in pipelines
    (Taylor & Francis, 2016-07-20) Alipooramirabad, H; Paradowska, AM; Ghomashchi, R; Kotousov, A; Hoye, N
    In the present study, the Welding Institute of Canada (WIC) restraint test was used to simulate the restraint conditions of full-scale girth welds on energy pipelines to ascertain the influence of welding process parameters on welding stresses. Finite element models are developed, and validated with neutron diffraction measurements, to evaluate the welding stresses for under-matched, matched and over-matched welds. The effects of heat input, wall thickness and variable restraint lengths of WIC sample are systematically investigated. As a practical outcome, this work can help in selection of the appropriate restraint length for WIC tests to simulate the specified stress conditions in the pipeline, and, ultimately, reduce the risk of Hydrogen Assisted Cold Cracking (HACC) in high strength low alloy. © 2021 Informa UK Limited
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    Residual stress and critical crack size before and after post-weld heat-treatment
    (Materials Research Proceedings, 2016-07-03) Law, M; Paradowska, AM; Hoye, N; Grace, P
    Post-weld heat-treatment (PWHT) is performed to reduce residual stress, but is not always possible to perform. The residual stresses on a thick section weld on a gas pipeline were determined before and after PWHT to assess residual stress and critical defect sizes. © The Authors
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    Residual stresses in titanium aerospace components formed via additive manufacture
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2013-12-02) Hoye, N; Li, H; Cuiuri, D; Paradowska, AM
    Additive manufacturing (AM) using arc-wire based metal deposition has been suggested as one method to reduce the costs associated with production of titanium components, particularly within the aerospace sector. In the present study gas tungsten arc welding (GTAW) with automated wire addition was used to additively manufacture (AM) a representative thin-walled aerospace component from Ti-6AI-4V in a layer-wise manner. Residual strains, and hence stresses, were analysed quantitatively using neutron diffraction techniques on the KOWARI strain scanner at the OPAL research facility operated by the Australian Nuclear Science and Technology Organisation (ANSTO). Results showed that residual strains within such an AM sample could be measured with relative ease using the neutron diffraction method. Residual stress levels were found to be greatest in the longitudinal direction and concentrated at the interface between the base plate and deposited wall. Difficulties in measurement of lattice strains in some discrete locations were ascribed to the formation of the formation of localised texturing where α-Ti laths form in aligned colonies within prior β-Ti grain boundaries upon cooling. Observations of microstructure reveal 'basket-weave' morphology typical of welds in Ti-6AI-4V. Microhardness measurements show a drop in hardness in the top region of the deposit, indicating a dependence on thermal cycling from sequential welds. Time-of-flight neutron diffraction has been proposed to analyse stresses in both the α-Ti and β-Ti phases simultaneously as well as inter-granular strains. This study forms part of a wider investigation into the suitability of arc-wire based deposition techniques for the additive manufacture of titanium components.
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    Stress in thin wall structures made by layer addivite manufacturing
    (Materials Research Forum LLC, 2016-07-03) Luzin, V; Hoye, N
    Manufacturing of thin wall structures is one of the main applications of additive manufacturing, where it has significant advantages over traditional milling and machining techniques or welded analogues. Such thin walled structures are common in structural aerospace components, and are also frequently made from titanium alloys. For such large-scale components, layer deposition strategy is more advantageous rather than a pixel-wise deposition approach due to the demand for high productivity and size requirements. Several techniques can be used to produce layer-wise build-ups, including laser-powered Direct Metal Deposition (DMD) process or gas tungsten arc welding (GTAW). Although, in the general case of arbitrary thin wall structures the stress distribution is complex, for some simple geometries, the stress state is simple and can be well characterized within a model by a single parameter representing a layer deposition stress in the steady-state regime. The model calculations were verified by experimental results on a thin-walled sample component that was manufactured from Ti-6Al-4V by GTAW with the residual stresses measured using KOWARI neutron strain scanner at the OPAL research reactor (ANSTO). © The Authors