Documents disponibles écrits par cet auteur

Effect of particle properties on particle percolation behaviour in a packed bed / H.P. Zhu in Minerals engineering, Vol. 22 N° 11 (Octobre 2009) 

Public ISBD [article]  in Minerals engineering > Vol. 22 N° 11 (Octobre 2009) . - pp. 961–969 Titre : Effect of particle properties on particle percolation behaviour in a packed bed Type de document : texte imprimé Auteurs : H.P. Zhu, Auteur ; M. Rahman, Auteur ; A. B. Yu, Auteur Année de publication : 2009 Article en page(s) : pp. 961–969 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Discrete  element  modelling  Particle  size  Mineral  processing  Process  control Résumé : Spontaneous inter-particle percolation is a very important phenomenon related to the mixing/segregation of particulate materials. Many studies have been conducted to understand the mechanisms governing the percolation behaviours in the past. However, previous work has a lack of systematic investigation on the effect of particle properties. In this work, a layer of small particles passing through a packed bed under gravity is analysed by means of the discrete element method. Percolation behaviour in terms of percolation velocity and radial dispersion is studied. The effect of percolating particle properties, including sliding friction and damping coefficients between percolating and packing particles, density and diameter ratios of percolating to packing particles and Young’s modulus of percolating particles, on the percolation behaviour is considered. It is observed that the damping coefficient and diameter ratio are the two dominant parameters that significantly affect the percolation behaviour. In particular, increasing the damping coefficient or decreasing the diameter ratio would increase the percolation velocity and decrease the radial dispersion. The sliding friction coefficient, Young’s modulus and density ratio have limited effects on the percolation behaviour. Two formulas have been, respectively, proposed to describe the dependences of percolation velocity and interaction force between percolating and packing particles on damping coefficient and diameter ratio. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509000788 [article] Effect of particle properties on particle percolation behaviour in a packed bed [texte imprimé] / H.P. Zhu, Auteur ; M. Rahman, Auteur ; A. B. Yu, Auteur . - 2009 . - pp. 961–969. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 22 N° 11 (Octobre 2009) . - pp. 961–969 Mots-clés : Discrete  element  modelling  Particle  size  Mineral  processing  Process  control Résumé : Spontaneous inter-particle percolation is a very important phenomenon related to the mixing/segregation of particulate materials. Many studies have been conducted to understand the mechanisms governing the percolation behaviours in the past. However, previous work has a lack of systematic investigation on the effect of particle properties. In this work, a layer of small particles passing through a packed bed under gravity is analysed by means of the discrete element method. Percolation behaviour in terms of percolation velocity and radial dispersion is studied. The effect of percolating particle properties, including sliding friction and damping coefficients between percolating and packing particles, density and diameter ratios of percolating to packing particles and Young’s modulus of percolating particles, on the percolation behaviour is considered. It is observed that the damping coefficient and diameter ratio are the two dominant parameters that significantly affect the percolation behaviour. In particular, increasing the damping coefficient or decreasing the diameter ratio would increase the percolation velocity and decrease the radial dispersion. The sliding friction coefficient, Young’s modulus and density ratio have limited effects on the percolation behaviour. Two formulas have been, respectively, proposed to describe the dependences of percolation velocity and interaction force between percolating and packing particles on damping coefficient and diameter ratio. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509000788

The evolution of crack-tip stresses during a fatigue overload event / A. Steuwer in Acta materialia, Vol. 58 N° 11 (Juin 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 11 (Juin 2010) . - pp. 4039–4052 Titre : The evolution of crack-tip stresses during a fatigue overload event Type de document : texte imprimé Auteurs : A. Steuwer, Auteur ; M. Rahman, Auteur ; A. Shterenlikht, Auteur Année de publication : 2011 Article en page(s) : pp. 4039–4052 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Plasticity-induced  closure  Stress  intensity  factor  Crack-tip  stress  field  Overload  Retardation Résumé : The mechanisms responsible for the transient retardation or acceleration of fatigue crack growth subsequent to overloading are a matter of intense debate. Plasticity-induced closure and residual stresses have often been invoked to explain these phenomena, but closure mechanisms are disputed, especially under conditions approximating to generalised plane strain. In this paper we exploit synchrotron radiation to report very high spatial resolution two-dimensional elastic strain and stress maps at maximum and minimum loading measured under plane strain during a normal fatigue cycle, as well as during and after a 100% overload event, in ultra-fine grained AA5091 aluminium alloy. These observations provide direct evidence of the material stress state in the vicinity of the crack-tip in thick samples. Significant compressive residual stresses were found both in front of and behind the crack-tip immediately following the overload event. The effective stress intensity at the crack-tip was determined directly from the local stress field measured deep within the bulk (plane strain) by comparison with linear elastic fracture mechanical theory. This agrees well with that nominally applied at maximum load and 100% overload. After overload, however, the stress fields were not well described by classical K fields due to closure-related residual stresses. Little evidence of overload closure was observed sometime after the overload event, in our case possibly because the overload plastic zone was very small. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410001588 [article] The evolution of crack-tip stresses during a fatigue overload event [texte imprimé] / A. Steuwer, Auteur ; M. Rahman, Auteur ; A. Shterenlikht, Auteur . - 2011 . - pp. 4039–4052. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 11 (Juin 2010) . - pp. 4039–4052 Mots-clés : Plasticity-induced  closure  Stress  intensity  factor  Crack-tip  stress  field  Overload  Retardation Résumé : The mechanisms responsible for the transient retardation or acceleration of fatigue crack growth subsequent to overloading are a matter of intense debate. Plasticity-induced closure and residual stresses have often been invoked to explain these phenomena, but closure mechanisms are disputed, especially under conditions approximating to generalised plane strain. In this paper we exploit synchrotron radiation to report very high spatial resolution two-dimensional elastic strain and stress maps at maximum and minimum loading measured under plane strain during a normal fatigue cycle, as well as during and after a 100% overload event, in ultra-fine grained AA5091 aluminium alloy. These observations provide direct evidence of the material stress state in the vicinity of the crack-tip in thick samples. Significant compressive residual stresses were found both in front of and behind the crack-tip immediately following the overload event. The effective stress intensity at the crack-tip was determined directly from the local stress field measured deep within the bulk (plane strain) by comparison with linear elastic fracture mechanical theory. This agrees well with that nominally applied at maximum load and 100% overload. After overload, however, the stress fields were not well described by classical K fields due to closure-related residual stresses. Little evidence of overload closure was observed sometime after the overload event, in our case possibly because the overload plastic zone was very small. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410001588