Discontinuously reinforced aluminium matrix composites are fast emerging as engineering materials and competing with common metals and alloys. They are gaining significant acceptance because of higher specific strengt...Discontinuously reinforced aluminium matrix composites are fast emerging as engineering materials and competing with common metals and alloys. They are gaining significant acceptance because of higher specific strength, specific modulus and good wear resistance as compared to ordinary unreinforced alloys. Reinforcing particles or short fibers normally used are silicon carbide and alumina which are added externally. Recently it has been shown that alumina particles can be produced in-situ by reaction with metallic oxides reduced by aluminium. Alumina particles thus produced are dispersed in the aluminium matrix and the elementary metal gives solid solution strengthening of the matrix. In-situ particulate composites in comparison with conventional cast particulate composites produced by external addition promote cleaner interface, eliminates interface incompatibility of the matrices with the reinforcements, help to achieve greater thermodynamic stability of reinforcement particles in the matrix at elevated temperature and also increase the possibility of developing coherency between the matrix and particles formed in-situ. The morphology and the distribution of particles strongly influence the physical and mechanical properties of composites. In the present investigation, iron ore was added to molten aluminium, aluminium-magnesium and aluminium-silicon alloys by vortex method. The iron oxides present in the iron ore are observed to react with aluminium, magnesium resulting in production of Al2O3, MgO and metallic iron which dissolved in liquid aluminium. The composites thus produced were cast into cast iron die. The mechanical properties of the composites were evaluated. The dry sliding wear behavior of the cast composites was studied at different loads and different sliding velocities using Pin-On-Disk configuration wear testing machine. The worn surfaces and the wear debris were also analyzed using optical microscope and scanning electron microscope.展开更多
Fluid-particle systems as commonly encountered in chemical, metallurgical and petroleum industries are mostly polydisperse in nature. However, the relations used to describe fluid-particle interactions are originally ...Fluid-particle systems as commonly encountered in chemical, metallurgical and petroleum industries are mostly polydisperse in nature. However, the relations used to describe fluid-particle interactions are originally derived from monodisperse systems, with ad hoc modifications to account for polydispersity. In previous work it was shown that for bidisperse systems with moderate diameter ratios of 1：2 to 1：4, this approach leads to discrepancies, and a correction factor is needed. In this work we demonstrate that this correction factor also holds for more extreme diameter ratios of 1：5, 1：7 and 1： 10, although the force on the large particles is slightly overestimated when using the correction factor. The main origin of the correction is that the void surrounding the large particles becomes less in case ofa bidisperse mixture, as compared to a monodisperse system with the same volume fraction. We further investigated this discrepancy by calculating the volume per particle by means of Voronoi tessellation.展开更多
In this talk I report on recent work related to the dynamical generation of baryonic resonances, some made up from pseudoscalar meson-baryon, others from vector meson-baryon and a third type from two meson-one baryon ...In this talk I report on recent work related to the dynamical generation of baryonic resonances, some made up from pseudoscalar meson-baryon, others from vector meson-baryon and a third type from two meson-one baryon systems. We can establish a correspondence with known baryonic resonances, reinforcing conclusions previously drawn and bringing new light on the nature of some baryonic resonances of higher mass.展开更多
文摘Discontinuously reinforced aluminium matrix composites are fast emerging as engineering materials and competing with common metals and alloys. They are gaining significant acceptance because of higher specific strength, specific modulus and good wear resistance as compared to ordinary unreinforced alloys. Reinforcing particles or short fibers normally used are silicon carbide and alumina which are added externally. Recently it has been shown that alumina particles can be produced in-situ by reaction with metallic oxides reduced by aluminium. Alumina particles thus produced are dispersed in the aluminium matrix and the elementary metal gives solid solution strengthening of the matrix. In-situ particulate composites in comparison with conventional cast particulate composites produced by external addition promote cleaner interface, eliminates interface incompatibility of the matrices with the reinforcements, help to achieve greater thermodynamic stability of reinforcement particles in the matrix at elevated temperature and also increase the possibility of developing coherency between the matrix and particles formed in-situ. The morphology and the distribution of particles strongly influence the physical and mechanical properties of composites. In the present investigation, iron ore was added to molten aluminium, aluminium-magnesium and aluminium-silicon alloys by vortex method. The iron oxides present in the iron ore are observed to react with aluminium, magnesium resulting in production of Al2O3, MgO and metallic iron which dissolved in liquid aluminium. The composites thus produced were cast into cast iron die. The mechanical properties of the composites were evaluated. The dry sliding wear behavior of the cast composites was studied at different loads and different sliding velocities using Pin-On-Disk configuration wear testing machine. The worn surfaces and the wear debris were also analyzed using optical microscope and scanning electron microscope.
基金funded by the Nederlandse Organisatievoor Wetenschappelijk Onderzoek(Netherlands Organization forScientific Research,NWO)
文摘Fluid-particle systems as commonly encountered in chemical, metallurgical and petroleum industries are mostly polydisperse in nature. However, the relations used to describe fluid-particle interactions are originally derived from monodisperse systems, with ad hoc modifications to account for polydispersity. In previous work it was shown that for bidisperse systems with moderate diameter ratios of 1：2 to 1：4, this approach leads to discrepancies, and a correction factor is needed. In this work we demonstrate that this correction factor also holds for more extreme diameter ratios of 1：5, 1：7 and 1： 10, although the force on the large particles is slightly overestimated when using the correction factor. The main origin of the correction is that the void surrounding the large particles becomes less in case ofa bidisperse mixture, as compared to a monodisperse system with the same volume fraction. We further investigated this discrepancy by calculating the volume per particle by means of Voronoi tessellation.
基金Supported by EU contract No. MRTN-CT-2006-035482 (FLAVIAnet)contracts FIS2006-03438 FIS2008-01661 from MICINN(Spain)+1 种基金Generalitat de Catalunya contract 2005SGR-00343support of the European Community-Research Infrastructure Integrating Activity 'Study of Strongly Interacting Matter' (HadronPhysics2, Grant Agreement n. 227431)under the Seventh Framework Programme of EU
文摘In this talk I report on recent work related to the dynamical generation of baryonic resonances, some made up from pseudoscalar meson-baryon, others from vector meson-baryon and a third type from two meson-one baryon systems. We can establish a correspondence with known baryonic resonances, reinforcing conclusions previously drawn and bringing new light on the nature of some baryonic resonances of higher mass.
