Sorptive stress estimation: an important key to the mechano-sorptive effect in wood
Houška, Mladen (Author), Koc, Pino (Author)

URLURL - Presentation file, Visit http://dx.doi.org/10.1023/A:1009897822196 This link opens in a new window

The mechano-sorptive effect (MSE) can be classified as a very interesting, but not yet completely explained phenomenon of wood behaviour. We therefore decided to try to discover its most relevant mechanisms, by conducting two independent series of measurements: accurate measurements of bending deflections on small, clear specimens of spruce wood in changeable climate conditions; and average moisture content (MC) in three parts of the cross-section of unloaded dummy samples. The paper emphasises on the sorptive part of MSE. A computer simulation of the wetting experiment is done to determine the space and time-dependent MC field in the cross-section of the sample. Using a so-called inverse problem identification method, where the equivalence of the computed and measured responses of the numerical model and real sample is imposed, we identified unknown material properties. The solution of the inverse problem enabled us simultaneously to estimate the moisture diffusion coefficients and to determine the MC field. Two kinds of boundary conditions were used in simulations. To estimate the magnitude of sorption stresses a numerical analysis using Finite Element Method (FEM) was done. The sorptive stresses resulting from the nonhomogeneous MC distribution in the sample were obtained. The decisive factor is the gradient of moisture content and resulting sorptive stresses must be taken into account because their magnitude is of the same order as the load induced bending stresses. Our experiments and the calculations following enabled us to conclude that the reason for MS behaviour could be the simultaneous action of permanent load stresses and the transient triaxial sorptive stress state.

Keywords:mehanika, obnašanje lesa, mehano-sorptivni učinek, sorptivna napetost, nestacionarni vlažnostni gradienti, mechanics, wood behaviour, sorptive stresses, changeable moisture content, inverse identification method, mechano-sorptive effect, MSE, numerical simulation
Work type:Not categorized (r6)
Tipology:1.01 - Original Scientific Article
Organization:FS - Faculty of Mechanical Engineering
Number of pages:str. 81-98
Numbering:Vol. 4, no. 1
ISSN on article:1385-2000
COBISS.SI-ID:3749659 Link is opened in a new window
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Record is a part of a journal

Title:Mechanics of time-dependent materials
Shortened title:Mech. time-depend. mater.
COBISS.SI-ID:3749403 This link opens in a new window

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