Browsing by Author "Guo, Hua"

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    Influence of deposition strategies on residual stress in wire + arc additive manufactured titanium Ti-6Al-4V
    (MDPI, 2022-01-28) Ahmad, Bilal; Zhang, Xiang; Guo, Hua; Fitzpatrick, Michael E.; MacHado Santos Carvalho Neto, Leonor; Williams, Stewart
    Wire + arc additive manufacturing (WAAM) is a modern manufacturing process that has opened new possibilities for rapid builds and reductions in material wastage. This paper explores residual stress in WAAM Ti-6Al-4V walls built using three different deposition strategies: single bead, parallel path, and oscillation path. The effect of interlayer hammer peening and interlayer temperature was investigated for the single bead walls. We also examined the residual stress in compact-tension (C(T)) coupons extracted from large builds (walls) with crack orientation either parallel with or perpendicular to the build direction. This type of sample is often used for the measurement of the fatigue crack growth rate. The contour method was used for experimental determinations of residual stress. In addtion, residual stress in the C(T) coupons was estimated by finite element (FE) analysis. A good agreement was achieved between the contour method and FE analysis. The oscillation-path wall had the lowest residual stress values. For the single bead walls built with various process conditions, residual stress was significantly reduced after removing the substrate. A interlayer temperature of 110 °C resulted in much higher residual stress values in the wall (both tensile and compressive) compared to the continuous build, with much higher interlayer temperature.
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    Investigation of adhesive joining strategies for the application of a multi-material light rail vehicle
    (MDPI, 2021-11-18) Liu, Yiding; Carnegie, Craig; Ascroft, Helen; Li, Wenhao; Han, Xiao; Guo, Hua; Hughes, Darren J.
    To meet the high demand for lightweight energy-efficient and safe structures for transport applications, a current state-of-the-art light rail vehicle structure is under development that adopts a multi-material design strategy. This strategy creates the need for advanced multi-material joining technologies. The compatibility of the adhesive with a wide range of material types and the possibility of joining multi-material structures is also a key advantage to its success. In this paper, the feasibility of using either epoxy or polyurethane adhesive joining techniques applied to the multi-material vehicle structure is investigated. Importantly, consideration is given to the effect of variation in bond thickness for both families of structural adhesives. Multi-material adhesively bonded single lap joints with different adhesives of controlled bond thicknesses were manufactured and tested in order to experimentally assess the shear strength and stiffness. The torsional stiffness and natural frequency of the vehicle were modelled using a global two-dimensional finite element model (FEM) with different adhesive properties, and the obtained vehicle performances were further explained by the coupon-level experimental tests. The results showed that the vehicle using polyurethane adhesive with a target bond thickness of 1.0 mm allowed for optimal modal frequency and weight reduction.
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    Prediction of residual stress within linear friction welds using a computationally efficient modelling approach
    (Elsevier, 2017-11-08) Buhr, Clement; Ahmad, Bilal; Colegrove, Paul A.; McAndrew, Anthony R.; Guo, Hua; Zhang, Xiang
    Modelling the mechanical mixing occurring at the interface of a linear friction weld (LFW) is complex, making it difficult to study the development of residual stresses within real engineering workpieces. To address this, a sequentially-coupled numerical model of a Ti-6Al-4V LFW was developed, bypassing the modelling of the oscillations by applying the heat at the weld interface and sequentially removing rows of elements to account for the burn-off. Increasing the rubbing velocity was found to numerically increase the peak of residual stress while narrowing the distribution. Only small changes arose from increasing the applied pressure or changing the oscillation direction. Predictions suggested a strong correlation between the phase 3 temperature profile and the residual stress field subsequently created. Validation against neutron diffraction and contour method are also presented. This approach provides a computationally efficient technique to study the residual stress development within large 3D structures.