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Andreas Mortensen - One of the best experts on this subject based on the ideXlab platform.
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Capillarity in pressure infiltration: improvements in characterization of high-temperature systems
Journal of Materials Science, 2012Co-Authors: Alain Léger, N. R. Calderon, Raphaël Charvet, Willy Dufour, C. Bacciarini, Ludger Weber, Andreas MortensenAbstract:In the pressure infiltration of metal matrix composites, molten metal is injected under external pressure into a porous preform of the reinforcing material. Equilibrium capillary parameters characterizing wetting for this process are summarized in plots of metal saturation versus applied pressure, also known as drainage curves. Such curves can be measured in our laboratory during a single experiment with an infiltration apparatus designed to track the rate of metal penetration into porous preforms under conditions characteristic of metal matrix composite processing (temperatures in excess of 1000 °C and pressures in the order of 10 MPa). For such measurements to be valid, infiltration of the preform with molten metal must be mechanically quasi-static, i.e., the metal must flow at a rate sufficiently low for the metal pressure to be essentially uniform across the preform at all times. We examine this requirement quantitatively, using a finite-difference model that simulates the unsaturated unidirectional ingress of molten metal into a Ceramic Particle preform of finite width. We furthermore present improvements in the experimental apparatus developed in our laboratory to measure the entire drainage curve in a single experiment. We compare numerical results with new experimental data for the copper/alumina system to show (i) that pressurization rates sufficiently low for quasi-static infiltration can be produced with this apparatus, and (ii) that taking the relative permeability equal to the saturation yields better agreement with experiment than does the expression originally proposed by Brooks and Corey.
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fracture of high volume fraction Ceramic Particle reinforced aluminium under multiaxial stress
Acta Materialia, 2010Co-Authors: Aude Hauert, A. Rossoll, Andreas MortensenAbstract:Circumferentially notched cylindrical bars of high volume fraction Al2O3 Particle reinforced aluminium are tested in tension to probe the role of tensile stress triaxiality on damage and failure of such materials. The transverse strain is monitored with a specially designed video extensometer. A significant dependence of the peak average stress and failure strain on notch radius is observed. Finite-element simulations of the tests are conducted on the basis of a micromechanical model derived from earlier studies of damage and failure of these composites under uniaxial tensile deformation (Journal of the Mechanics and Physics of Solids 2009;57:1781). The simulations show that stress and strain distributions within the notched composite samples deviate significantly from predictions of Bridgman’s simplified analysis. Comparison with data shows that, whereas calculations capture satisfactorily the evolution of the average composite flow stress as a function of notch radius at small strains, the notched samples damage faster and fail at strains lower than predicted. Two phenomena may explain the discrepancy, namely (i) damage coalescence beyond a threshold level, and (ii) the incapacity of the matrix to sustain large hydrostatic stresses, which results from the presence of internal surfaces (cracked Particles and possibly matrix voiding).
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Particle fracture in high-volume-fraction Ceramic-reinforced metals: Governing parameters and implications for composite failure
Journal of the Mechanics and Physics of Solids, 2009Co-Authors: Aude Hauert, A. Rossoll, Andreas MortensenAbstract:Abstract Weibull parameters of angular alumina Particles are determined from experimental tensile test data on high-Ceramic-content metal matrix composites using a micromechanical model that accounts for internal damage in the form of Particle cracking, the dominant damage mode in these composites. The fraction of broken Particles is assessed from the drop of Young's modulus and Particle fracture is assumed to be stress controlled. Two extreme load-sharing modes, namely a purely local and a global load-sharing mode, are considered to account for the load redistribution due to Particle fracture. Consistent powder strength parameters can be thus “back-calculated” for Particles that are embedded in different Al–Cu matrices. On the other hand, this calculation fails for pure Al matrix composites, which exhibit a much larger strain to failure than Al–Cu matrix composites. It is shown that for Al matrix composites, the role of plastic (composite) strain on Particle fracture constitutes a second parameter governing Particle damage. This finding is rationalized by Particle–Particle interactions in these tightly packed Ceramic Particle-reinforced composites, and by the increase of matrix stress heterogeneity that is brought with increasing plastic strain. Failure of the alloyed matrix composites is well described by the (lower bound) local load-sharing micromechanical model, which predicts a catastrophic failure due to an avalanche of damage. The same model predicts failure of pure aluminium matrix composites to occur at the onset of tensile instability, also in agreement with experimental results once the role of plastic strain on damage accumulation is accounted for.
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investigation of crack tip plasticity in high volume fraction particulate metal matrix composites
Engineering Fracture Mechanics, 2004Co-Authors: Ali Miserez, A. Rossoll, Andreas MortensenAbstract:Crack-tip strain fields in high volume fraction Ceramic Particle reinforced metal matrix composites are assessed using photoelastic measurements. It is shown that the size of the significant crack-tip plastic zones that form in these materials depends on the type and diameter of the reinforcement and on the matrix material. This plastic zone size correlates well with the macroscopic toughness values assessed through J -integral testing. The composites are thus ‘‘metallic’’ in the sense that their toughness is mostly composed of plastic energy dissipation around the crack tip. Plastic deformation also induces marked constraint effects that influence the shape of the surface strain fields. It is shown that finite element analysis must be three-dimensional to describe these strain fields, as two-dimensional plane-stress analysis fails to reproduce the experimental data. � 2004 Elsevier Ltd. All rights reserved.
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quantification of microdamage phenomena during tensile straining of high volume fraction Particle reinforced aluminium
Acta Materialia, 2001Co-Authors: M Kouzeli, L Weber, San C Marchi, Andreas MortensenAbstract:Particle reinforced composites are produced by infiltrating Ceramic Particle beds with 99.99% Al. Resulting materials feature a relatively high volume fraction (40-55 vol. pet) of homogeneously distributed reinforcement. The evolution of damage during tensile straining of these composites is monitored using two indirect methods; namely by tracking changes in density and in Young's modulus. Identification and quantification of the active damage mechanisms is conducted on polished sections of failed tensile specimens: Particle fracture and void formation in the matrix are the predominant damage micromechanisms in these materials. The damage parameter derived from the change in density at a given strain is found to be one to two orders of magnitude smaller than the parameter based on changes in Young's modulus. A simple micromechanical analysis inspired by the observed damage micromechanisms is used to correlate the two indirect measurements of damage. The predictions of this analysis are in good agreement with experiment. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. AII rights reserved.
Zhenfang Zhang - One of the best experts on this subject based on the ideXlab platform.
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wear of Ceramic Particle reinforced metal matrix composites part i wear mechanisms
Journal of Materials Science, 1995Co-Authors: Zhenfang Zhang, Liangchi Zhang, Yiuwing MaiAbstract:Pin-on-disc dry sliding tests were carried out to study the wear mechanisms in a range of metal-matrix composites. 6061-aluminium alloys reinforced with 10 and 20 vol % SiC and Al 2 O 3 Particles were used as pin materials, and a mild steel disc was used as a counterface. A transition from mild wear to severe wear was found for the present composites; the wear rate increased by a factor of 10 2 . The effects of the Ceramic Particles on the transition load and wear with varying normal pressure were thoroughly investigated. Three wear mechanisms were identified: abrasion in the running-in period, oxidation during steady wear at low load levels, and adhesion at high loads. A higher Particle volume fraction raised the transition load but increased the wear rate in the abrasion and adhesion regimes. Increase of Particle size was more effective than increase of volume fraction to prolong the transition from mild wear to adhesive wear. The reasons for different wear mechanisms were determined by analyses of the worn surfaces and wear debris
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wear of Ceramic Particle reinforced metal matrix composites
Journal of Materials Science, 1995Co-Authors: Zhenfang Zhang, Liangchi Zhang, Yiuwing MaiAbstract:Wear experiments have shown that when the applied normal stress exceeds a critical value, a transition occurs from the regime of mild wear to that of adhesive wear. As a result, the wear rate of Particle-reinforced aluminium composites increases by a hundred-fold. Based on dislocation and delamination theories, a criterion is proposed for determining the critical transition load, and a quantitative model is developed for adhesive wear in a wear system of a steel disc sliding against aluminium matrix composite pins. Experimental results of four kinds of metal-matrix composites confirm the validity of the criterion and the model.
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wear of Ceramic Particle reinforced metal matrix composites
Journal of Materials Science, 1995Co-Authors: Zhenfang Zhang, Liangchi Zhang, Yin Wing MaiAbstract:Pin-on-disc dry sliding tests were carried out to study the wear mechanisms in a range of metal-matrix composites. 6061-aluminium alloys reinforced with 10 and 20 vol% SiC and Al2O3 Particles were used as pin materials, and a mild steel disc was used as a counterface. A transition from mild wear to severe wear was found for the present composites; the wear rate increased by a factor of 102. The effects of the Ceramic Particles on the transition load and wear with varying normal pressure were thoroughly investigated. Three wear mechanisms were identified: abrasion in the running-in period, oxidation during steady wear at low load levels, and adhesion at high loads. A higher Particle volume fraction raised the transition load but increased the wear rate in the abrasion and adhesion regimes. Increase of Particle size was more effective than increase of volume fraction to prolong the transition from mild wear to adhesive wear. The reasons for different wear mechanisms were determined by analyses of the worn surfaces and wear debris.
Yiuwing Mai - One of the best experts on this subject based on the ideXlab platform.
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wear of Ceramic Particle reinforced metal matrix composites
Journal of Materials Science, 1995Co-Authors: Zhenfang Zhang, Liangchi Zhang, Yiuwing MaiAbstract:Wear experiments have shown that when the applied normal stress exceeds a critical value, a transition occurs from the regime of mild wear to that of adhesive wear. As a result, the wear rate of Particle-reinforced aluminium composites increases by a hundred-fold. Based on dislocation and delamination theories, a criterion is proposed for determining the critical transition load, and a quantitative model is developed for adhesive wear in a wear system of a steel disc sliding against aluminium matrix composite pins. Experimental results of four kinds of metal-matrix composites confirm the validity of the criterion and the model.
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wear of Ceramic Particle reinforced metal matrix composites part i wear mechanisms
Journal of Materials Science, 1995Co-Authors: Zhenfang Zhang, Liangchi Zhang, Yiuwing MaiAbstract:Pin-on-disc dry sliding tests were carried out to study the wear mechanisms in a range of metal-matrix composites. 6061-aluminium alloys reinforced with 10 and 20 vol % SiC and Al 2 O 3 Particles were used as pin materials, and a mild steel disc was used as a counterface. A transition from mild wear to severe wear was found for the present composites; the wear rate increased by a factor of 10 2 . The effects of the Ceramic Particles on the transition load and wear with varying normal pressure were thoroughly investigated. Three wear mechanisms were identified: abrasion in the running-in period, oxidation during steady wear at low load levels, and adhesion at high loads. A higher Particle volume fraction raised the transition load but increased the wear rate in the abrasion and adhesion regimes. Increase of Particle size was more effective than increase of volume fraction to prolong the transition from mild wear to adhesive wear. The reasons for different wear mechanisms were determined by analyses of the worn surfaces and wear debris
Hellwig Christian - One of the best experts on this subject based on the ideXlab platform.
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A Mixed Ceramic-Metal Sphere-Pac Concept
'Informa UK Limited', 2015Co-Authors: Pouchon, Manuel A., Nakamura Masahiro, Hellwig ChristianAbstract:Particle bed arrangements (e.g. sphere-pac and vipac) are considered as alternative fuel-forms for nuclear fission of actinides. The fuel material is potentially UO2, MOX or an Inert Matrix such as yttria-stabilized zirconia. A disadvantage of Ceramic Particle fuel is its low thermal conductivity at startup. The macroscopic structure of a Particle bed (e.g. spherical Particles in sphere-pac) hinders heat transport prior to sintering. To remedy this situation, a novel cer-met concept is proposed and studied in this work. In the sphere-pac model with two well differing size fractions, one material can be distributed evenly into the other one. In this case, the Ceramic material (e.g. yttria stabilized zirconia) and the metallic component (e.g. zirconium) are the large and small size fractions respectively. Calculations for this initial fuel configuration show a significant enhancement of the thermal conductivity. Sintering occurs following startup and especially at the center of the fuel. The macroscopic sphere-pac arrangement then transforms into a porous-pellet-like structure. Sintering experiments have been performed to investigate these effects. In the cer-met arrangement the restructuring was enhanced. Therefore heat transport improves even as the metallic component becomes oxidized
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a mixed Ceramic metal sphere pac concept
Journal of Nuclear Science and Technology, 2002Co-Authors: Pouchon A Manuel, Nakamura Masahiro, Hellwig ChristianAbstract:Particle bed arrangements (e.g. sphere-pac and vipac) are considered as alternative fuel-forms for nuclear fission of actinides. The fuel material is potentially UO2, MOX or an Inert Matrix such as yttria-stabilized zirconia. A disadvantage of Ceramic Particle fuel is its low thermal conductivity at startup. The macroscopic structure of a Particle bed (e.g. spherical Particles in sphere-pac) hinders heat transport prior to sintering. To remedy this situation, a novel cer-met concept is proposed and studied in this work. In the sphere-pac model with two well differing size fractions, one material can be distributed evenly into the other one. In this case, the Ceramic material (e.g. yttria stabilized zirconia) and the metallic component (e.g. zirconium) are the large and small size fractions respectively. Calculations for this initial fuel configuration show a significant enhancement of the thermal conductivity. Sintering occurs following startup and especially at the center of the fuel. The macroscopic sph...
Liangchi Zhang - One of the best experts on this subject based on the ideXlab platform.
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wear of Ceramic Particle reinforced metal matrix composites part i wear mechanisms
Journal of Materials Science, 1995Co-Authors: Zhenfang Zhang, Liangchi Zhang, Yiuwing MaiAbstract:Pin-on-disc dry sliding tests were carried out to study the wear mechanisms in a range of metal-matrix composites. 6061-aluminium alloys reinforced with 10 and 20 vol % SiC and Al 2 O 3 Particles were used as pin materials, and a mild steel disc was used as a counterface. A transition from mild wear to severe wear was found for the present composites; the wear rate increased by a factor of 10 2 . The effects of the Ceramic Particles on the transition load and wear with varying normal pressure were thoroughly investigated. Three wear mechanisms were identified: abrasion in the running-in period, oxidation during steady wear at low load levels, and adhesion at high loads. A higher Particle volume fraction raised the transition load but increased the wear rate in the abrasion and adhesion regimes. Increase of Particle size was more effective than increase of volume fraction to prolong the transition from mild wear to adhesive wear. The reasons for different wear mechanisms were determined by analyses of the worn surfaces and wear debris
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wear of Ceramic Particle reinforced metal matrix composites
Journal of Materials Science, 1995Co-Authors: Zhenfang Zhang, Liangchi Zhang, Yiuwing MaiAbstract:Wear experiments have shown that when the applied normal stress exceeds a critical value, a transition occurs from the regime of mild wear to that of adhesive wear. As a result, the wear rate of Particle-reinforced aluminium composites increases by a hundred-fold. Based on dislocation and delamination theories, a criterion is proposed for determining the critical transition load, and a quantitative model is developed for adhesive wear in a wear system of a steel disc sliding against aluminium matrix composite pins. Experimental results of four kinds of metal-matrix composites confirm the validity of the criterion and the model.
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wear of Ceramic Particle reinforced metal matrix composites
Journal of Materials Science, 1995Co-Authors: Zhenfang Zhang, Liangchi Zhang, Yin Wing MaiAbstract:Pin-on-disc dry sliding tests were carried out to study the wear mechanisms in a range of metal-matrix composites. 6061-aluminium alloys reinforced with 10 and 20 vol% SiC and Al2O3 Particles were used as pin materials, and a mild steel disc was used as a counterface. A transition from mild wear to severe wear was found for the present composites; the wear rate increased by a factor of 102. The effects of the Ceramic Particles on the transition load and wear with varying normal pressure were thoroughly investigated. Three wear mechanisms were identified: abrasion in the running-in period, oxidation during steady wear at low load levels, and adhesion at high loads. A higher Particle volume fraction raised the transition load but increased the wear rate in the abrasion and adhesion regimes. Increase of Particle size was more effective than increase of volume fraction to prolong the transition from mild wear to adhesive wear. The reasons for different wear mechanisms were determined by analyses of the worn surfaces and wear debris.