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Material Porosity (material + porosity)

Distribution by Scientific Domains

Engineering	75%

Selected Abstracts

Short Communication: application of a surrogate material in assessing the impact of porosity on re-ignition of wood-based materials

FIRE AND MATERIALS, Issue 2 2002
Behdad Moghtaderi
Re-ignition behaviour of charred solid fuels after extinction by water is studied. In this communication the effect of material porosity on re-ignition is investigated. A surrogate ceramic material is used so as to separate the pyrolysis and combustion processes from those associated with heat transfer. Experimental data are reported for different sample thickness and porosity, and varying heat flux and water application time. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Coupled damage and plasticity modelling in transient dynamic analysis of concrete

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 1 2002
Fabrice Gatuingt
Abstract In a concrete structure subjected to an explosion, for example a concrete slab, the material is subjected to various states of stress which lead to many modes of rupture. Closer to the explosive, a state of strong hydrostatic compression is observed. This state of stress produces an irreversible compaction of the material. Away from the zone of explosion, confinement decreases and the material undergoes compression with a state of stress, which is slightly triaxial. Finally, the compression wave can be reflected on a free surface and becomes a tensile wave, which by interaction with the compression wave, produces scabbing. We present, in this paper, a model aimed at describing these three failure modes. It is based on visco-plasticity and rate dependent damage in which a homogenization method is used in order to include the variation of the material porosity due to compaction. The model predictions are compared with several experiments performed on the same concrete. Computations of split Hopkinson tests on confined concrete, a tensile test with scabbing, and an explosion on a concrete slab are presented. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Numerical modelling of fluid flow in microscopic images of granular materials

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 1 2002
E. Masad
Abstract A program for the simulation of two-dimensional (2-D) fluid flow at the microstructural level of a saturated anisotropic granular medium is presented. The program provides a numerical solution to the complete set of Navier,Stokes equations without a priori assumptions on the viscous or convection components. This is especially suited for the simulation of the flow of fluids with different density and viscosity values and for a wide range of granular material porosity. The analytical solution for fluid flow in a simple microstructure of porous medium is used to verify the computer program. Subsequently, the flow field is computed within microscopic images of granular material that differ in porosity, particle size and particle shape. The computed flow fields are shown to follow certain paths depending on air void size and connectivity. The permeability tensor coefficients are derived from the flow fields, and their values are shown to compare well with laboratory experimental data on glass beads, Ottawa sand and silica sands. The directional distribution of permeability is expressed in a functional form and its anisotropy is quantified. Permeability anisotropy is found to be more pronounced in the silica sand medium that consists of elongated particles. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Neue Methoden zur Beurteilung der Betriebsfestigkeit im Fahrzeugauslegungs- und -absicherungsprozess

MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 10 2008
M. Brune
Fatigue strength; design and validation process; method development; load data simulation; lightweight design; short fibre reinforced polymers; material porosity; die casted aluminium Abstract Der moderne Auslegungs- und Absicherungsprozess in der Automobilindustrie beinhaltet experimentelle, messtechnische und auch rechnerische Methoden. Dieser Beitrag erläutert anhand von Beispielen neue Entwicklungen in der Betriebsfestigkeitsauslegung, insbesondere auf dem Gebiet der virtuellen Methoden. Dies bezieht sich zum einen auf die virtuelle Lastdatenermittlung, zum anderen auf die Verbesserung der rechnerischen Lebensdauerabschätzung. Hier werden zwei aktuelle Beispiele der Methodenentwicklung erläutert. Das erste Beispiel behandelt die Berücksichtigung von Werkstoffinhomogenitäten bei der Berechnung von Aluminium-Gussbauteilen, das zweite Beispiel beschreibt die Vorgehensweise der Auslegung von Bauteilen aus kurzfaserverstärkten Kunststoffen mittels eines neuen Berechnungsverfahrens. Advanced durability evaluation in vehicle design and validation process The modern process of evaluation and validation conducted in the automotive industry uses experimental, metrological, and calculation-based methods. Offering various examples, the present paper describes new developments in the determination and evaluation of operating strength, particularly in terms of virtual methods and their application in practice. The first point considered is the virtual determination of load data, the second is the improvement of calculated fatigue life. Two current examples in the development of methods are presented in this context: The first example examines the inhomogeneity of materials in calculating aluminium castings. The second example describes the approach taken in the configuration of components made of short-fibre-reinforced polymers, applying a new method of calculation. [source]