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Muhammad W.,University of Waterloo | Mohammadi M.,University of Waterloo | Kang J.,CanmetMATERIALS | Mishra R.K.,General Motors | Inal K.,University of Waterloo
International Journal of Plasticity | Year: 2015

Abstract Deformation twinning and texture evolution in hexagonal close-packed (HCP) metals lead to evolving flow stress asymmetry/anisotropy and evolving plastic anisotropy. These phenomena cause a significant change in the shape of the yield surface with accumulated plastic deformation which cannot be modeled accurately with traditional hardening laws. In this paper, an anisotropic continuum-based plasticity model is proposed to capture the large strain cyclic hardening behavior of magnesium alloys. Key in the current formulation is the incorporation of distortional hardening to model the evolving asymmetric/anisotropic hardening response of magnesium alloys for both monotonic and reverse loading paths. The hardening behavior is classified into three deformation modes: Monotonic Loading [ML], Reverse Compression [RC], and Reverse Tension [RT]. The deformation modes correspond to the different loading regimes of the cyclic hardening curve. Specifically, the ML mode corresponds to the initial in-plane tension and the initial in-plane compression from the annealed state, the RC mode corresponds to the in-plane compression following previous tension and the RT mode corresponds to the in-plane tension following previous compression. Three separate hardening laws are used to define the hardening response within each deformation mode. Moreover, a multi-yield surface modeling approach is used where a CPB06 type anisotropic yield surface is assigned to each deformation mode. The evolution of the anisotropy coefficients involved in the expression of the yield function, is considered to model distortional hardening within each deformation mode. The evolving anisotropy parameters are found by minimizing the difference between the model predictions and the experiments, together with the interpolation technique proposed by Plunkett et al. (2006). The proposed model is calibrated using monotonic and reverse loading experimental data for AZ31B and ZEK100 magnesium alloys. A strain rate independent elasto-plastic formulation is used to implement the proposed constitutive model as a user material subroutine (UMAT) in the commercial finite element software LS-DYNA®. The predictions of the model are compared against the experimental monotonic and cyclic (CTC and TCT) flow stresses and r-values of AZ31B and ZEK100 sheets along different test directions. An excellent agreement is found between the simulated and experimental results. © 2015 Elsevier Ltd. All rights reserved. Source


Simha C.H.M.,CanmetMATERIALS | Adibi-Asl R.,University of Toronto
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2015

It is shown that the extended variational theorem of Mura et al. (1965, "Extended Theorems of Limit Analysis," Q. Appl. Math., 23(2), pp. 171-179) can be applied to structures subjected to more than one load and be used to compute lower bound limit load multipliers. In particular, the multiplier proposed by Simha and Adibi-Asl (2011, "Lower Bound Limit Load Estimation Using a Linear Elastic Analysis," ASME J. Pressure Vessel Technol., 134(2), p. 021207), which can be computed using an elastic stress field, is shown to be a lower bound. Furthermore, it is demonstrated that lower bound limit load for cracked structures may also be computed using a subvolume selection method. No iterations or elastic modulus adjustment are required. Several analytical and numerical examples that illustrate the procedure are presented. Copyright © 2015 by ASME. Source


Shokrollahi Yancheshmeh M.,Laval University | Radfarnia H.R.,CanmetMATERIALS | Iliuta M.C.,Laval University
Journal of Natural Gas Science and Engineering | Year: 2016

Calcium looping process, on the basis of the reversible reaction between CaO and CO2, is a promising technology for capture of CO2 from different gas streams. The performance of CO2 sorbents could be easily influenced by the gas stream composition. As the exhaust gas stream generally contains a considerable amount of steam, a good understanding of its side effects on the performance of CaO-based sorbents is essential. However, there is not consensus on the mechanism with which the presence of steam during carbonation influences the CO2 capture performance and contradictory results have been reported regarding the effect of steam addition during calcination. This work aims to investigate the effect of steam addition during either carbonation or calcination on the reactivity of a home-made synthetic CaO sorbent containing 78 wt% CaO and 22 wt% Ca9Al6O18. Various concentrations of steam up to 9.5 vol% were provided during either carbonation or calcination for 15 carbonation-calcination cycles (carbonation: 650 or 550 °C; calcination: 800 °C). The morphology changes of the sorbent after cyclic carbonation-calcination experiments were studied in detail at different operating conditions. It was concluded that the sorbent reactivity was significantly increased for all concentrations of steam injected during carbonation step, due to the accelerated solid-state diffusion and steam catalysis. In case of steam addition during calcination, the carbonation performance was affected negatively or positively depending on the concentration of steam in the gas stream. For 2.3 vol% steam injection, the sorbent reactivity was worsened, while the presence of 9.5 vol% steam increased the CO2 capture capacity during 9 initial cycles. Such behavior was attributed to the intensified material sintering in the presence of steam during calcination step, which results in the formation of large pores and the decrease of specific surface area. © 2016 Elsevier B.V. Source


Hosokawa A.,Japan National Institute of Materials Science | Wilkinson D.S.,McMaster University | Kang J.,CanmetMATERIALS | Kobayashi M.,Toyohashi University of Technology | Toda H.,Toyohashi University of Technology
International Journal of Fracture | Year: 2013

The influences of work hardening behavior of materials on ductile fracture, and especially on void growth and coalescence, have been investigated in model materials by in-situ X-ray computed tomography (XCT) coupled with tensile deformation. The model materials contain an artificial void array embedded in a metal matrix. By producing such materials with different metal matrices (pure copper, brass, Glidcop = copper strengthened by Al2O3 nanoparticles), the influences of the work hardening behaviors on void growth and coalescence/linkage process are analyzed. This set of experiments were performed at Japanese synchrotron radiation facility SPring-8 BL20XU beamline, whereby the X-ray tomography setup with one of the highest spatial resolution in the world is available. This beamline however provides less brilliant X-rays compared to the ESRF ID15 beamline where the our previous experiments were performed Hosokava et al. (Acta Mater, 60:2829-2839, 2012), (Acta Mater, 61:1021-1036, 2013). To compensate for the X-ray absorption problems, the specimens to be tested have to be much smaller, making the experiments more difficult. Nevertheless, the growth and linkage behaviors of the artificial voids were successfully visualized, and the plastic strain whereby the linkage takes place (referred to as the linkage strain, hereafter) were quantitatively captured. The models for void coalescence developed by Thomason and by Pardoen and Hutchinson both predict coalescence rather well for both brass and Glidcop, even though the linkage events were found to be dominated by the meso/macro shear localization process. © 2013 Springer Science+Business Media Dordrecht. Source


Zeng Y.,CanmetMATERIALS | Guzonas D.,Chalk River Laboratories
JOM | Year: 2016

The supercritical water-cooled reactor (SCWR) is an innovative next generation reactor that offers many promising features, but the high-temperature high-pressure coolant introduces unique challenges to the long-term safe and reliable operation of in-core components, in particular the fuel cladding. To achieve high thermal efficiency, the Canadian SCWR concept has a coolant core outlet temperature of 625°C at 25 MPa with a peak cladding temperature as high as 800°C. International and Canadian research programs on corrosion issues in supercritical water have been conducted to support the SCWR concept. This paper provides a brief review of corrosion in supercritical water and summarizes the Canadian corrosion assessment work on potential fuel cladding materials. Five alloys, SS 347H, SS310S, Alloy 800H, Alloy 625 and Alloy 214, have been shown to have sufficient corrosion resistance to be used as the fuel cladding. Additional work, including tests in an in-reactor loop, is needed to confirm that these alloys would work as the fuel cladding in the Canadian SCWR. © 2015, Her Majesty the Queen in Right of Canada. Source

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