DEFORMATION-BEHAVIOR OF CERAMIC SLABS BY NONUNIFORM DRYING

The present paper is to study the transient deformation characteristic s of molded ceramics undergoing nonuniform drying. The linear viscoela sticity was assumed for the strain-stress analysis. Three dimensional equations of the strain-stress as well as heat and moisture transfer w ere solved numerically by the Galerkin finite element method using iso parametric parameters of twenty-nodes so to allow easily the applicati on to any feature of ceramics. Both the analysis and experiments were carried out to be compared on the behaviors of drying and deformation for a slab clay in preheating and constant drying rate periods. When t he bottom surface of the slab was shielded to model the nonuniform dry ing, a warp phenomenon to the opposite side of the shielded surface wa s observed experimentally as drying by hot air heating proceeds. The b ehavior could be successively simulated by the present theoretical mod el. The degree of warp became remarkable with a rise in air temperatur e or nonuniformity of drying. The surface area exposed to the atmosphe re was subjected to a comparatively large tensional stress through dry ing. The tensile stresses on the top surface were significantly larger than on the bottom surface.