Stresses and Strains in Elastic, Viscoelastic, and Plastic Materials during Drying

The mechanistic theory of drying is developed for the purpose of stress and strain analysis in wet clay-like materials subjected to convective drying. The aim of these studies is to show the difference in stress and strain patterns for cases when the material is considered to be elastic, viscoelastic, or elastic-plastic. Such an analysis is justified by the fact that many materials under drying, e. g., clay-like or woody materials, reveal different mechanical properties and safer, mostly inelastic deformations. In addition, inelastic models are able to describe some additional phenomena as, for example, stress reverse that often appears in dried materials. It is displayed through comparison of the experimental measurements with the numerical results obtained on the basis of inelastic constitutive equations applied to drying materials. These results show that drying models that include inelastic deformations are more realistic and present more natural stress and strain patterns than the purely elastic model. The analysis is presented on an example of kaolin-clay plate subjected to convective drying. The numerical results concerning inelastic deformations are visualized on plots and photographs taken from the samples tested experimentally.