Effect of moisture on the behaviour of an extruded clay paste

16th ESAFORM Conference on Material Forming (ESAFORM 2013), Univ Aveiro, Aveiro, PORTUGAL, APR 22-24, 2013International audienceIn the industrial process, the moisture of the clay sheet obtained by extrusion and pressed to form a tile varies in time. It depends on the nature and the mixing of the raw materials during the production. In order to model and understand the influence of the moisture on the pressing step, it is necessary to determine the parameters of the rheological and tribological laws. A study of the rheological behaviour, based on free compression tests on cylinder samples, allowed to use an elasto-visco-plastic behaviour for the extruded clay paste. The different constitutive parameters were estimated by an inverse analysis based on the experimental force/displacement curves. The identification was performed with the optimisation algorithm implemented in the commercial software Forge 2009. The influence of the water content in the paste on the rheological parameters was identified and fitted using linear models. To understand the influence of the moisture, we simulated a compression test, using Forge involving the shaping of a tile lug. This geometry is representative of the state of stress during the pressing of the tile, in an area currently subjected to defects. The numerical model shows that an increase of eighteen percent of the moisture, allows to decrease by half the pressing force