THERMOMECHANICAL APPROACH TO SHRINKING AND CRACKING PHENOMENA IN DRYING

Abstract

Abstract The thermomechanics of partly saturated porous materials is presented as a basis for the construction of mechanistic theory of drying. Based on the balance of mass, momentum, energy, entropy, and the thermodynamics of irreversible processes the constitutive laws for heat and mass transfer and the physical relations between stresses, strains, moisture content and the temperature are developed. Using the London-Heitler's formulas for cohesion and the Condon-Morse curve performing the bond energy of two atoms versus their distance, a theoretical strength of material during drying process is estimated. By analogy to Griffith's concept, a fracture criterion is formulated. Finally, the acoustic emission as a possible method for detection of fracture process in dried materials is discussed. Keywords: DeformationsDrying aspectExperimental evidenceFractureMaterial strengthModelingSaturated mediaStresses ACKNOWLEDGMENT This work was carried out as a part of research project No. TO9C 005 12 sponsored by the Polish State Committee for Scientific Research in the year 1999.