Browsing by Author "Proust, G"

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    Keynote: Modelling the quasi-static and high-strain rate deformation behaviour of magnesium alloy AZ31
    (Scientech, 2015-07-14) Proust, G; Li, L; Flores-Johnson, EA; Shen, LM; Muránsky, O
    In hexagonal close-packed (hcp) metals, plastic deformation is accommodated by different slip and twinning systems. Various factors affect the activation of the deformation mechanisms: alloy composition, grain size, temperature of deformation, strain rate and loading direction. The multiplicity of deformation mechanisms that can be activated and the dependence on loading conditions explain the observed asymmetry and anisotropy on the hardening behaviour and texture evolution. It is therefore important to be able to characterise these deformation mechanisms for specific loading conditions to gain a thorough understanding of the mechanical behaviour of hcp materials. Modern microscopy techniques, such as electron backscatter diffraction (EBSD), enable the quantitative analysis of twinning which is an important deformation mechanics for magnesium alloys. These characterisation techniques allow a better understanding of the way materials deform and provide valuable information for predicting their behaviour. For example using such techniques one can determine the different twinning modes that have contributed to deformation but also the volume fraction of material that has twinned. These microscopy techniques have enabled modellers to better understand the contribution of twinning in the hardening behaviour of the materials and to devise schemes to incorporate the effects of twinning on the hardening response or/and texture evolution of hcp materials. In this work we are investigating the deformation behaviour of magnesium alloys AZ31 under quasi-static and high-strain rate loading. The high-strain rate experiments were carried out using a Hopkinson bar and the microstructure of the deformed samples was measured using EBSD. The experimental results were used to calibrate and test the robustness of a strain-dependent visco-plastic self-consistent crystal plasticity model. © 2015 Scientech
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    Residual stress measurements of lean duplex stainless steel welded sections
    (Elsevier, 2021-08-08) Li, DX; Paradowska, AM; Uy, B; Wang, J; Proust, G; Azad, SK; Huang, YR
    Lean duplex stainless steel (LDSS) has been increasingly utilised in engineering applications due to its excellent durability, corrosion resistance, as well as superior structural and economic benefits. Moreover, compared to cold-form sections, welded members have significant structural advantages, and thus, have been widely used in many engineering practices. However, as one of the key factors affecting the performance of structural components, residual stresses of LDSS welded sections have not been sufficiently investigated. Therefore, square and H-shaped LDSS welded sections were considered in the present experimental programme. Accurate measurements of the tensile and compressive residual stresses were conducted through the non-destructive neutron diffraction method. As LDSS is a dual-phase material, neutron diffraction measurement was repeated twice for each specimen to obtain the individual phase residual stresses (ferrite-phase, α and austenite-phase, γ). Hardness analysis, as well as microstructural characterisation using optical microscopy and electron backscatter diffraction (EBSD) were thereafter performed to ascertain the volume fraction of each phase, based on which the residual stresses along the direction of interest were successfully converted. According to the obtained experimental results, the authors recommended analytical models for the LDSS fabricated square sections and proposed new models for the H-sections, through which the residual stress distributions for welded LDSS sections can be accurately predicted. In addition, the recommended/proposed analytical models for LDSS sections were further compared with their counterparts previously developed for high-strength steel (HSS) and ultra-high-strength steel (UHSS) welded sections. © 2021 Elsevier Ltd