Squeezing Flow of Suspensions: Flow Regime Evaluation from Energy Approach

International audienceThe squeezing flow geometry is here used to investigate the properties of concentrated suspensions. The suspensions consist in idealized system of smooth hard spheres dispersed in a yield stress colloidal gel. During the squeezing action, the material structure evolves with energy variation due to particle displacement and interaction. The goal of our study is to evaluate the energy evolution from a Fourier analysis as a function of solid volume fraction and compression velocity

On the optimisation of a texture analyser in squeeze flow geometry

The original contribution is available at http://www.sciencedirect.com/science/article/pii/S0263224106000327International audienceThis paper describes how the range of application of a texture analyser, used for mechanical tests of solids and liquids in the food and cosmetics industry, can be extended to reproduce squeeze flow geometry. It describes the necessary optimisation of the device to ensure parallelism and thermal regulation of the plates during tests. The error on the load cell and the instrument compliance are evaluated. The influence of these artefact measurements is investigated in terms of interpretation of rheological properties of materials

The Back Extrusion Test as a Technique for Determining the Rheological and Tribological Behaviour of Yield Stress Fluids at Low Shear Rates

The original contribution is available at http://www.ar.ethz.ch/International audienceA new method is developed to determine the rheological and tribological behaviour of viscoplastic fluids using a back extrusion test. In back extrusion geometry, the material is forced to flow in the gap between the inner and the outer cylinder. Such a flow is modelled by a Bingham constitutive law under different wall boundary conditions (stick, slip with friction and perfect slip). When steady-state flow is reached, an apparent shear rate is computed. The analysis of the inner cylinder penetration force versus the penetration depth helps us to develop a method to identify the fluid rheological and tribological properties. This method is based on an inverse analysis to identify the fluid behaviour parameters from experiments performed at different ram velocities and with different apparatus geometries. In order to study more complex fluids (Herschell-bulkley rheological behaviour, for example), an equivalent flow curve is plotted from tests characterized by different average shear rates. The tribological behaviour is identified using different wall boundary conditions, varying the surface roughness of the cylinders. The method is applied to oil/sugar suspension and plasticine. Rheological and tribological behaviours are identified and results are compared with those obtained under steady state shear flow. The obtained rheological parameters are close to those provided by the common rheological methods (difference lower than 15 %)

Use of ram extruder as a combined rheo-tribometer to study the behaviour of high yield stress fluids at low strain rate

International audienceWe propose in this work to provide an efficient and simple extruder device able to evaluate the rheological and tribological behaviour of high yield stress fluids, such as extrudible materials. An extruder able to measure simultaneously both the friction force acting on the extruder wall and the total extrusion force is developed. Based on previous studies, an efficient and accurate method of data analysis is then proposed and applied in order to obtain both a flow curve and a tribological law. Experimental tests are performed on soft modelling clay, kaolin paste and cement-based materials. Results are compared to conventional rheometry measurements. This comparison helps to evaluate the accuracy of the proposed experimental device and procedure

Kinetics of internal structure evolution in gypsum board exposed to standard fire

International audienceGypsum is often used as passive fire protection. Indeed, its latent heat effect reduces heat transfer through the structure. To improve composition and physical properties of such material, it is necessary to model its behaviour. Heat and mass transfer have to be considered in the model. For a better understanding of phenomena occurring during a fire event, it is important to study the porosity. In this study, a porosity measurement protocol is developed. The porosity distribution along the thickness of large board sample subjected to standard fire (ISO 834) on one face is studied. In addition, scale effect is taken into account. Finally, the effect of temperature and microstructure are analysed

Experimental study of thermo-chemical behaviour of gypsum based material under standard ISO 834 fire condition

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Structuration de panneaux de gypse Etude en condition incendie

ISBN 978-2-915913-28-6International audienc

Mortar physical properties evolution in extrusion flow

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Evolution des propriétés d'un mortier durant son extrusion

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Le test de compression simple : mise en œuvre et exploitation en présence de fluides alimentaires

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