Approaches to the Moisture Content Monitoring Intimber Elements: Development of a Resistive Method

Abstract:

The scope of this work is based on the use of resistive method to quantify the water content in timber elements. For an in-depth mapping, we adapted a multiplexed technique derived from geophysics based on a maximum crossing of current lines to obtain topography of measures sweeping the space boundary conditions being defined by the sample. The calibration of these measures is completed by a gammadensimetry laboratory method which allows access to water profiles along a preferred direction. Nevertheless, the resistive method is penalized by logarithmic laws linking moisture and resistivity. So, we develop a hybrid method for coupling the data obtained to diffusion models: it will provide complementary information where resistivity and gammadensimetry are no longer effective. The developed experimental protocol allows employing the selected method and optimizing the diffusion properties (diffusion coefficient and convective exchange coefficient) injected into a characterization algorithm (Nelder-Mead’s simplex inversion method) based on a finite difference method for the Fick’s diffusion law determination integrating orthotropic and non- linear properties. Overlap between electric field and density measurements and the numerical simulation tool are possible.

• Periodical: Advanced Materials Research (Volume 778)
• Pages: 335-341
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.778.335
• Online since: September 2013
• Authors: Tuan Anh N'Guyen, Nicolas Angellier, Sabine Caré, Laurent Ulmet, Frédéric Dubois
• Keywords: Diffusion Model, Gammadensimetry, Resistivity, Wood Moisture

References

[1] Dubois, F., Petit, C., Sauvat, N., Peuchot, B., Cremona, C., Fournely, E., 2004. A Study about the mechanic behaviour of the timber bridge of Merle. 8th Word Conference on Timber Engineering WCTE2004, June 14-17 Lahti.

[2] Da Rocha, M.C., Da Silva, L.M., Appoloni, C.R., Portezan Filho, O., Lopes, F., Melquiades, F.L., et al., 2001. Moisture profile measurements of concrete samples in vertical water flow by gamma ray transmission method. Radiat Phys Chem, 61 (3-6): 567-9.

DOI: 10.1016/s0969-806x(01)00334-6

[3] Villain, G and Thierry, M., 2006. Gammadensimetry: a method to determine drying and carbonation profiles in concrete. ND&E Int. 39 (4) 328-337.

DOI: 10.1016/j.ndteint.2005.10.002

[4] Loke M.H. and Barker R.D. 1996b. Practical techniques for 3D resistivity surveys and data inversion. Geophysical Prospecting, 44, 499-524.

DOI: 10.1111/j.1365-2478.1996.tb00162.x

[5] Lasserre B., Modélisation thermo-hygro-mécanique du comportement différé de poutres de structure en bois, PhD Thesis, University of Bordeaux I, (2000).

[6] Nedler J.A., Downhill simplex method, Computer Journal, 7: 308-313, (1965).

[7] Kouchade A.C., Détermination en routine de la diffusivité massique dans le bois par méthode inverse à partir de la mesure électrique en régime transitoire, PhD Thesis, Engref, Nancy, (2004).