FUNDAMENTAL-STUDY ON SHRINKAGE OF FORMED CLAY DURING DRYING - VISCOELASTIC STRAIN-STRESS AND HEAT MOISTURE TRANSFER

The theoretical analysis was developed to predict the deformation characteristic of formed clay during a drying process in a ceramic production. The three dimensional strain-stress distribution as well as heat and moisture transfer in a slab shape of clay were simultaneously analyzed by a finite element method. Linear viscoelasticity was assumed for the strain-stress analysis to account the effect of creep. The calculated result agreed well with an experimental result performed for a slab clay heated by hot air flow during the preheating and constant drying rate periods. A large tensional stress, which may generate a crack, was observed initially around the surface area. It was also found that the time behavior of the volume change of the formed clay is significantly influenced on the drying conditions and/or the drying rate.