EXPERIMENTAL AND FEM – SUPPORTED INVESTIGATION OF WET CERAMIC CLAY EXTRUSION FOR THE DETERMINATION OF STRESS DISTRIBUTIONS ON THE APPLIED TOOLS ’ SURFACES

Aiming at assessing the stress distribution on the surface of a die mandrel during the extrusion of ceramic products, the flow of wet ground clay was simulated both in a ram extrusion device and by a FEM based model, considering the von Mises crite-rion for the flow stress, the associative flow rule and the rigid-viscoplastic constitu-tive equation. The friction between clay and die is approached by the Tresca bound-ary condition, which proves a more realistic approach than the Coulomb friction law for the contact conditions between a plastically deforming material and a rigid sur-face. The Tresca friction factor and the material parameters of the constitutive model are determined through comparison of experimental and theoretical results. The dis-tributions of clay sliding velocity and normal and frictional stress on the mandrel sur-face are then assessed through the numerical simulation model. It is found that no sticking areas appear on the mandrel surface