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 criterion for the flow stress, the associative flow rule and the rigid-viscoplastic constitutive equation. The friction between clay and die is approached by the Tresca boundary condition, which proves a more realistic approach than the Coulomb friction law for the contact conditions between a plastically deforming material and a rigid surface. The Tresca friction factor and the material parameters of the constitutive model are determined through comparison of experimental and theoretical results. The distributions of clay sliding velocity and normal and frictional stress on the mandrel surface are then assessed through the numerical simulation model. It is found that no sticking areas appear on the mandrel surface.