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Theoretical Study of Stress Reversal Phenomena in Drying of Porous Media
Author(s) -
Kowalski Stefan Jan
Publication year - 2002
Publication title -
developments in chemical engineering and mineral processing
Language(s) - English
Resource type - Journals
eISSN - 1932-2143
pISSN - 0969-1855
DOI - 10.1002/apj.5500100404
Subject(s) - acoustic emission , materials science , viscoelasticity , capillary action , stress (linguistics) , porous medium , porosity , composite material , ceramic , mechanics , physics , philosophy , linguistics
Drying of capillary porous materials may generate internal stresses, the magnitude of which depends on both the drying techniques and the mechanical properties of dried materials. Acoustic emission (EA), a method to monitor for damage control during drying, shows an enhanced emission of acoustic impulses and energy from the material in some stages of drying. A particularly interesting phenomenon is the occurrence of enhanced emission of the acoustic impulses at the final stage of drying, that is, at the time when the drying induced stresses are expected to disappear. This phenomenon is explained by the stress reversal, i.e. the change of stress signs from negative (compressive) inside the material at the beginning to the positive (tensional) at the final stage of drying. A theoretical analysis is presented in this paper using the viscoelastic model. Stress reversal was predicted and analyzed from drying cylinders of ceramics‐like material and wood.