Deformation Behavior of Ceramic Slabs by Nonuniform Drying

Abstract

ABSTRACT The presenr paper is to study the transient deformation characteristics of molded ceramics undergoing nonunifom drying. The linear viscoelasticity was assumed for the strain-stress analysis. Three dimensional equations of the strain-stress as well as heat and moisture transfer werc solved numerically by the Galerkln finlle element melhod using isoparametric parameters of twenty-nodes so to allow easily the application to any feature of ceramics. Both the analysis and experiments were carried out to be compared on the behavior of drying and deformation for a slab clay in preheating and constant drying rare periods. When the bottom surface of the slab uras shielded to model the nonuniform drying. a warp phenomrnon to the opposite side of the shielded surface was observed experimentally as drying by hot air heating proceeds. The behavior could be successively simulaled by the present theoretical model. The degree of warp became rcmarkabel with a rise in air temperature or nonuniformity of drying. The surface area exposed to the atmosphere was subjected to a comparatively large tensional stress through drying. The tensile sltresses on the top surface were significantly larger than on the bottom surface. Keywords and Phrases: clayconvective dryingdrying shrinkageheat and mass transferhygro-smin and stressmoldingviscoelasticity