Damien Rangeard

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

We 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.

Study of tribological behaviour of fresh mortar against a rigid plane wall

The interaction between a fresh cement-based material and a solid wall represents a considerable consumption of energy during an extrusion proces. In this article, the tribological behaviour of extrudible mortar and rigid wall friction is studied using a tribometer especially developed in the laboratory. Dynamic friction coefficient is highlighted. For fixed wall roughness, the friction velocity effect is analysed. Then, for fixed friction velocity, the roughness effect is analysed. Finally, the material structure evolution near the wall and the material erosion are analysed. L,interaction de matériaux à base cimentaire frais et une paroi solide représente une consommation énergétique importante dans les procédés d,extrusion. Dans cet article, le comportement tribologique d,un mortier extrudable et d,une paroi rigide est étudié au moyen d,un tribomètre développé et mis au point au laboratoire. Dans les travaux, le coefficient de frottement dynamique est tout d,abord mis en évidence. Pour une paroi de rugosité fixée, l,effet de la vitesse de frottement est ensuite analysé. Dans une partie suivante, à vitesse de frottement fixée, l,effet de la rugosité de la paroi est analysé. Enfin, l,évolution de la structure du matériau au voisinage de la paroi est présentée et discutée ainsi que l,érosion.

Extrusion Flow Modelling of Concentrated Mineral Suspensions

This study deals with the stability of the flow of cement-based materials induced by the extrusion forming process. Recently, such process has gained much interest because of its involvement in 3D printing process. The occurrence of the relative filtration of the fluid through the solid part of the material is governed by a competition between the permeability of the granular skeleton and the velocity of the extrusion process. Based on extrusion tests, two types of plastic behavior are proposed to describe the extrusion properties. The extrusion flow are tested under different conditions, such as sand proportion, ram velocity, die diameter, etc. The moisture contents on extrudates are calculated to describe the fluid filtration and the development of solid volume fraction. The experimental results are to be compared with the model prediction of the extrusion tests.