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Corrosion and self-healing behaviour of AZ91D magnesium alloy in ethylene glycol/water solutions / L. Wang in Materials and corrosion, Vol. 63 N° 8 (Août 2012) 

Public ISBD [article]  in Materials and corrosion > Vol. 63 N° 8 (Août 2012) . - pp. 713–719 Titre : Corrosion and self-healing behaviour of AZ91D magnesium alloy in ethylene glycol/water solutions Type de document : texte imprimé Auteurs : L. Wang, Auteur ; T. Zhou, Auteur ; J. Liang, Auteur Année de publication : 2013 Article en page(s) : pp. 713–719 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : AZ91D  magnesium  alloys;  corrosion  behaviour;  ethylene  glycol;  self-healing  behaviour Résumé : Corrosion behaviour of magnesium alloy-based engine parts in cooling system is an urgent fundamental issue in automotive field where magnesium alloys are increasingly used. In the present work, the corrosion behaviour of AZ91D magnesium alloys in various ethylene glycol/water solutions was studied by electrochemical measurements and immersion tests at room temperature. The surfaces of the samples after immersion tests were examined using scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that the corrosion rates of AZ91D magnesium alloys decreased with the increase of ethylene glycol concentration in ethylene glycol/water solutions and the corrosion process was dominated by pitting corrosion. A continuous protective film transferred from corrosion products was formed on the corroded surface after sufficient immersion duration in ethylene glycol/water solutions, which is able to heal the corrosion pits. The self-healing behaviour inhibited the further corrosion of AZ91D magnesium alloy. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201106131/abstract [article] Corrosion and self-healing behaviour of AZ91D magnesium alloy in ethylene glycol/water solutions [texte imprimé] / L. Wang, Auteur ; T. Zhou, Auteur ; J. Liang, Auteur . - 2013 . - pp. 713–719. Génie mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 63 N° 8 (Août 2012) . - pp. 713–719 Mots-clés : AZ91D  magnesium  alloys;  corrosion  behaviour;  ethylene  glycol;  self-healing  behaviour Résumé : Corrosion behaviour of magnesium alloy-based engine parts in cooling system is an urgent fundamental issue in automotive field where magnesium alloys are increasingly used. In the present work, the corrosion behaviour of AZ91D magnesium alloys in various ethylene glycol/water solutions was studied by electrochemical measurements and immersion tests at room temperature. The surfaces of the samples after immersion tests were examined using scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that the corrosion rates of AZ91D magnesium alloys decreased with the increase of ethylene glycol concentration in ethylene glycol/water solutions and the corrosion process was dominated by pitting corrosion. A continuous protective film transferred from corrosion products was formed on the corroded surface after sufficient immersion duration in ethylene glycol/water solutions, which is able to heal the corrosion pits. The self-healing behaviour inhibited the further corrosion of AZ91D magnesium alloy. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201106131/abstract

Deformation of oxide scales on Fe-20Cr alloy under compressive stress / C. H. Zhou in Materials and corrosion, Vol. 61 N° 8 (Août 2010) 

Public ISBD [article]  in Materials and corrosion > Vol. 61 N° 8 (Août 2010) . - pp. 676–680 Titre : Deformation of oxide scales on Fe-20Cr alloy under compressive stress Type de document : texte imprimé Auteurs : C. H. Zhou, Auteur ; H. T. Ma, Auteur ; L. Wang, Auteur Année de publication : 2010 Article en page(s) : pp. 676–680 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Compressive  stress;  deformation;  gain  boundary  sliding;  oxide  scale;  slip Résumé : The behavior of oxide scales on Fe-20Cr alloy was investigated in constant load at 1173 K in air. The objective was to understand the effect of mechanical loading on the deformation of oxide scales. It was carried out mainly by comparison of surface morphologies of oxidized specimens observed by scanning electronic microscope (SEM). In all cases, the oxide scales formed on specimens without stress showed a flat surface. However, oxide scales formed on specimens after 20 h of oxidation under a stress of 8 MPa (strain 3.07%) showed slip band characteristics. Furthermore, for longer oxidation time up to 65 h, slip bands formed under a low stress of 2 MPa (strain 1.19%), and grain boundary sliding became the main surface feature for the specimens subjected to a stress of 5 MPa (strain 2.53%). Two typical deformation forms are illustrated in the work. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.200905292/abstract [article] Deformation of oxide scales on Fe-20Cr alloy under compressive stress [texte imprimé] / C. H. Zhou, Auteur ; H. T. Ma, Auteur ; L. Wang, Auteur . - 2010 . - pp. 676–680. Génie mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 61 N° 8 (Août 2010) . - pp. 676–680 Mots-clés : Compressive  stress;  deformation;  gain  boundary  sliding;  oxide  scale;  slip Résumé : The behavior of oxide scales on Fe-20Cr alloy was investigated in constant load at 1173 K in air. The objective was to understand the effect of mechanical loading on the deformation of oxide scales. It was carried out mainly by comparison of surface morphologies of oxidized specimens observed by scanning electronic microscope (SEM). In all cases, the oxide scales formed on specimens without stress showed a flat surface. However, oxide scales formed on specimens after 20 h of oxidation under a stress of 8 MPa (strain 3.07%) showed slip band characteristics. Furthermore, for longer oxidation time up to 65 h, slip bands formed under a low stress of 2 MPa (strain 1.19%), and grain boundary sliding became the main surface feature for the specimens subjected to a stress of 5 MPa (strain 2.53%). Two typical deformation forms are illustrated in the work. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.200905292/abstract

Dilatancy of the interface between a structure and gravelly soil / G. Zhang in Géotechnique, Vol. LXI N° 1 (Janvier 2011) 

Public ISBD [article]  in Géotechnique > Vol. LXI N° 1 (Janvier 2011) . - pp. 75–84 Titre : Dilatancy of the interface between a structure and gravelly soil Type de document : texte imprimé Auteurs : G. Zhang, Auteur ; L. Wang, Auteur ; J.-M. Zhang, Auteur Année de publication : 2011 Article en page(s) : pp. 75–84 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Gravels  Soil/structure  interaction  Constitutive  relations  Laboratory  tests  Shear  strength Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Dilatancy is one of the key properties of the soil–structure interface. A number of monotonic and cyclic shear tests were analysed to derive the rules and the dilatancy mechanism of the interface between a structure and a gravelly soil; diverse influential factors were considered, such as soil type, roughness of the structure and normal stress. The volumetric change due to the dilatancy consists of a reversible and irreversible dilatancy component, each of which has different mechanisms, different rules and different control factors. The reversible dilatancy component is strongly dependent on the direction of the applied shear after an initial application of shear loading. The irreversible dilatancy component gradually increases owing to the continued application of shear and exhibits a close relationship with the evolution of the physical state. The volumetric change that is due to the dilatancy mainly depends on part of the tangential displacement which corresponds to the deformation of the soil that is constrained by the structure; such a part of the tangential displacement is significantly dependent on the state of the entire tangential displacement, on the normal stress and on the features of both the structure and the soil. The roughness of the structure, the behaviour of the soil and the normal stress have significant effects on the dilatancy behaviour of the interface. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.051 [article] Dilatancy of the interface between a structure and gravelly soil [texte imprimé] / G. Zhang, Auteur ; L. Wang, Auteur ; J.-M. Zhang, Auteur . - 2011 . - pp. 75–84. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. LXI N° 1 (Janvier 2011) . - pp. 75–84 Mots-clés : Gravels  Soil/structure  interaction  Constitutive  relations  Laboratory  tests  Shear  strength Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Dilatancy is one of the key properties of the soil–structure interface. A number of monotonic and cyclic shear tests were analysed to derive the rules and the dilatancy mechanism of the interface between a structure and a gravelly soil; diverse influential factors were considered, such as soil type, roughness of the structure and normal stress. The volumetric change due to the dilatancy consists of a reversible and irreversible dilatancy component, each of which has different mechanisms, different rules and different control factors. The reversible dilatancy component is strongly dependent on the direction of the applied shear after an initial application of shear loading. The irreversible dilatancy component gradually increases owing to the continued application of shear and exhibits a close relationship with the evolution of the physical state. The volumetric change that is due to the dilatancy mainly depends on part of the tangential displacement which corresponds to the deformation of the soil that is constrained by the structure; such a part of the tangential displacement is significantly dependent on the state of the entire tangential displacement, on the normal stress and on the features of both the structure and the soil. The roughness of the structure, the behaviour of the soil and the normal stress have significant effects on the dilatancy behaviour of the interface. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.051

Effect of residual stresses on the onset of yielding in a Zr-based metallic glass / L. Wang in Acta materialia, Vol. 59 N° 20 (Décembre 2011) 

Public ISBD [article]  in Acta materialia > Vol. 59 N° 20 (Décembre 2011) . - pp. 7627–7633 Titre : Effect of residual stresses on the onset of yielding in a Zr-based metallic glass Type de document : texte imprimé Auteurs : L. Wang, Auteur ; H. Bei, Auteur ; Y.F. Gao, Auteur Année de publication : 2012 Article en page(s) : pp. 7627–7633 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Residual  stresses  Onset  of  yielding  Metallic  glasses  Nanoindentation  Glass  transition Résumé : Indentation experiments were performed on as-cast and elastically-bent-and-constrained Zr-based metallic glass samples to investigate the effect of strain rate and residual stresses on the onset of yielding in the material. The critical shear stress for the onset of yielding in the as-cast sample was found to be insensitive to the applied strain rate. By contrast, in the elastically-stressed sample, the maximum contact pressure from the Hertzian stress field at the onset of yielding was found to largely decrease under tensile residual stress, but only slightly increase under compressive residual stress. Despite the different residual stresses, the effective shear stress, i.e. the superimposition of residual and Hertzian stress fields, for the onset of yielding in the Zr-based metallic glass was essentially a constant. The constancy of the effective stress for the onset of yielding was discussed in light of a critical excess volume associated with the atomic structure upon loading. ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645411006665 [article] Effect of residual stresses on the onset of yielding in a Zr-based metallic glass [texte imprimé] / L. Wang, Auteur ; H. Bei, Auteur ; Y.F. Gao, Auteur . - 2012 . - pp. 7627–7633. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 59 N° 20 (Décembre 2011) . - pp. 7627–7633 Mots-clés : Residual  stresses  Onset  of  yielding  Metallic  glasses  Nanoindentation  Glass  transition Résumé : Indentation experiments were performed on as-cast and elastically-bent-and-constrained Zr-based metallic glass samples to investigate the effect of strain rate and residual stresses on the onset of yielding in the material. The critical shear stress for the onset of yielding in the as-cast sample was found to be insensitive to the applied strain rate. By contrast, in the elastically-stressed sample, the maximum contact pressure from the Hertzian stress field at the onset of yielding was found to largely decrease under tensile residual stress, but only slightly increase under compressive residual stress. Despite the different residual stresses, the effective shear stress, i.e. the superimposition of residual and Hertzian stress fields, for the onset of yielding in the Zr-based metallic glass was essentially a constant. The constancy of the effective stress for the onset of yielding was discussed in light of a critical excess volume associated with the atomic structure upon loading. ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645411006665

Improved multiple point nonlinear genetic algorithm based performance adaptation using least square method / Y. G. Li in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 3 (Mars 2012) . - 10 p. Titre : Improved multiple point nonlinear genetic algorithm based performance adaptation using least square method Type de document : texte imprimé Auteurs : Y. G. Li, Auteur ; M. F. Abdul Ghafir, Auteur ; L. Wang, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Engines  Gas  turbine  power  stations  Genetic  algorithms  Least  squares  approximations  Regression  analysis  Shafts Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : At off-design conditions, engine performance model prediction accuracy depends largely on its component characteristic maps. With the absence of actual characteristic maps, performance adaptation needs to be done for good imitations of actual engine performance. A nonlinear multiple point genetic algorithm based performance adaptation developed earlier by the authors using a set of nonlinear scaling factor functions has been proven capable of making accurate performance predictions over a wide range of operating conditions. However, the success depends on searching the right range of scaling factor coefficients heuristically, in order to obtain the optimum scaling factor functions. Such search ranges may be difficult to obtain and in many off-design adaption cases, it may be very time consuming due to the nature of the trial and error process. In this paper, an improvement on the present adaptation method is presented using a least square method where the search range can be selected deterministically. In the new method, off-design adaptation is applied to individual off-design point first to obtain individual off-design point scaling factors. Then plots of the scaling factors against the off-design conditions are generated. Using the least square method, the relationship between each scaling factor and the off-design operating condition is generated. The regression coefficients are then used to determine the search range of the scaling factor coefficients before multiple off-design points performance adaptation is finally applied. The developed adaptation approach has been applied to a model single-spool turboshaft engine and demonstrated a simpler and faster way of obtaining the optimal scaling factor coefficients compared with the original off-design adaptation method. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000003 [...] [article] Improved multiple point nonlinear genetic algorithm based performance adaptation using least square method [texte imprimé] / Y. G. Li, Auteur ; M. F. Abdul Ghafir, Auteur ; L. Wang, Auteur . - 2012 . - 10 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 3 (Mars 2012) . - 10 p. Mots-clés : Engines  Gas  turbine  power  stations  Genetic  algorithms  Least  squares  approximations  Regression  analysis  Shafts Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : At off-design conditions, engine performance model prediction accuracy depends largely on its component characteristic maps. With the absence of actual characteristic maps, performance adaptation needs to be done for good imitations of actual engine performance. A nonlinear multiple point genetic algorithm based performance adaptation developed earlier by the authors using a set of nonlinear scaling factor functions has been proven capable of making accurate performance predictions over a wide range of operating conditions. However, the success depends on searching the right range of scaling factor coefficients heuristically, in order to obtain the optimum scaling factor functions. Such search ranges may be difficult to obtain and in many off-design adaption cases, it may be very time consuming due to the nature of the trial and error process. In this paper, an improvement on the present adaptation method is presented using a least square method where the search range can be selected deterministically. In the new method, off-design adaptation is applied to individual off-design point first to obtain individual off-design point scaling factors. Then plots of the scaling factors against the off-design conditions are generated. Using the least square method, the relationship between each scaling factor and the off-design operating condition is generated. The regression coefficients are then used to determine the search range of the scaling factor coefficients before multiple off-design points performance adaptation is finally applied. The developed adaptation approach has been applied to a model single-spool turboshaft engine and demonstrated a simpler and faster way of obtaining the optimal scaling factor coefficients compared with the original off-design adaptation method. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000003 [...]

Modeling wall film formation and breakup using an integrated interface-tracking/discrete-phase approach / M. Arienti in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 3 (Mars 2011) 

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Nonlinear multiple points gas turbine off-design performance adaptation using a genetic algorithm / Y. G. Li in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 7 (Juillet 2011) 

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