DETERMINARE SI CUANTIFICARE NEDISTRUCTIVA A PROCESELOR DE DIFUZIUNE IN LEMN CU AJUTORUL METODEI IMAGISTICE CU NEUTRONI

David MANNES
Dr. - Department of Civil, Environmental and Geomatic Engineering, Institute for Building Materials (ETH) Adresa: 8093 Zurich, Switzerland
Tel: +41 44 632 3228. Fax: +41 44 632 1174.
E-mail: dmannes@ethz.ch

Walter SONDEREGGER
Eng. - Department of Civil, Environmental and Geomatic Engineering,
Institute for Building Materials (ETH)
E-mail: wsonderegger@ethz.ch

Stefan HERING
Eng. - Department of Civil, Environmental and Geomatic Engineering,
Institute for Building Materials (ETH)
E-mail: shering@ethz.ch

Eberhard LEHMANN
Dr. - Spallation Neutron Source (ASQ), Paul Scherrer Institute (PSI)
Adresa: 5232 Villigen, Switzerland
E-mail: eberhard.lehmann@psi.ch

Peter NIEMZ
Prof.Dr. - Dept. of Civil, Environmental and Geomatic Engineering
Institute for Building Materials (ETH)
E-mail: niemzp@ethz.ch

Rezumat:
         Procesele de difuziune in epruvetele de fag (Fagus sylvatica L.) si molid (Picea abies [L.] Karst.) au fost determinate si cuantificate cu ajutorul metodei imagistice cu neutroni (NI). Experimentele s-au efectuat la sediul NEUTRA al Institutului Paul Scherrer (PSI) din Villigen (Elvetia) utilizand un spectru termic cu neutroni. NI este o metoda de testare nedistructiva si neinvaziva, cu o mare senzitivitate pentru hidrogen si astfel pentru apa. Ca scop al acestui studiu, s-au stabilit procesele de difuziune in directie longitudinala la epruvete de lemn masiv expuse in diferite conditii (uscat-umed).Cu ajutorul NI a fost posibila determinarea distrubutiei locale si prin urmare cantitatea totala de apa absorbita de epruvete. Valorile calculate difera relativ putin fata de cele stabilite prin cantarire (= 3%). Metoda da profilul continutului de apa al intregii epruvete, permitand astfel analiza locala si temporala a proceselor de difuziune in cuprinsul epruvetei in aceeasi directie de transport (longitudinala). In baza acestor profiluri a fost posibil sa se calculeze coeficientii de difuziune in directia fibrelor respectand legea a doua a lui Fick.

Cuvinte cheie: difuziune, coeficient de difuziune, umiditate, imagistica cu neutroni, testare nedistructiva, lemn.

Bibliografie:
ALKAN, S., ZHANG, Y.L., LAM, F. (2007). Moisture Distribution Changes and Wetwood Behavior in Subalpine Fir Wood During Drying Using High X-Ray Energy Industrial CT. Drying Techn. 25:483-488.
BAETTIG, R., REMOND, R., PERRE, P. (2006). Measuring Moisture Content Profiles In A Board During Drying: A Polychromatic X-Ray System Interfaced With A Vacuum/Pressure Laboratory Kiln. Wood Sci. Techn. 40:261-274.
CAI, Z.Y. (2008). A New Method Of Determining Moisture Gradient In Wood. Forest Prod. J. 58:41-45
CRANK, J. - The Mathematics of Diffusion. Clarendon Press, Oxford, 1956
FRANDSEN, H.L., DAMKILDE, L., SVENSON, S. (2007). A Revised Multi-Fickian Moisture Transport Model To Describe Non-Fickian Effects In Wood. Holzforschung 61:563-572
HASSANEIN, R. (2006). Correction Methods for the Quantitative Evaluation of Thermal Neutron Tomography. Dissertation ETH Zurich, Zurich.
KOC, P., HOUSKA, M., STOK, B. (2003). Computer Aided Identification Of The Moisture Transport Parameters In Spruce Wood. Holzforschung 57:533-538.
LEHMANN, E., VONTOBEL, P., SCHERRER, P., NIEMZ, P. (2001a). Application of Neutron Radiography As Method In The Analysis Of Wood. Holz Roh- Werkst. 59 (6):463-471.
LEHMANN, E.H., VONTOBEL, P., WIEZEL, L. (2001b). Properties of the Radiography Facility NEUTRA at SINQ and its Potential for Use as European Reference Facility. Nondestructive Testing and Evaluation 16:191-202.
LEHMANN, E.H., FREI, G., KUHNE, G., BOILLAT, P. (2007). The Micro-Setup For Neutron Imaging: A Major Step Forward To Improve The Spatial Resolution. Nucl. Instrum. Meth. A 576:389-396.
MANNES, D., JOSIC, L., LEHMANN, E., NIEMZ, P. (2009) Neutron Attenuation Coefficients For Non-Invasive Quantification Of Wood Properties. Accepted for publication in Holzforschung.
MERELA, M., OVEN, P., SERSA, I., MIKAC U. (2009). A Single Point NMR Method for an Instantaneous Determination of the Moisture Content of Wood. Holzforschung 63:348-351.
MOUCHOT, N., THIERCELIN, F., PERRE, P., ZOULALIAN, A. (2006). Characterization Of Diffusional Transfers Of Bound Water And Water Vapor In Beech And Spruce. Maderas, ciencia y tecnología 8 (3):139-147.
NIEMZ, P., LEHMANN, E., VONTOBEL, P., HALLER, P., HANSCHKE, S. (2002). Investigations Using Neutron Radiography For Evaluations Of Moisture Ingress Into Corner Connections Of Wood. Holz Roh- Werkst. 60:118-126
OLEK, W., PERRE, P., WERES, J. (2005). Inverse Analysis Of The Transient Bound Water Diffusion In Wood. Holzforschung 59:38-45
PFRIEM, A. (2007). Untersuchungen zum Materialverhalten thermisch modifizierter Holzer fur deren Verwendung im Musikinstrumentenbau. Dissertation TU Dresden, Dresden.
PLAGGE, R., FUNK, M., SCHEFFLER, G., GRUNEWALD, J. (2006). Experimentelle Bestimmung der hygrischen Sorptionsisotherme und des Feuchtetransportes unter instationären Bedingungen. Bauphysik 28 (2):81-87.
SCHEEPERS, G., MOREN, T., RYPSTRA, T. (2007). Liquid Water Flow in Pinus Radiata During Drying. Holz Roh- Werkst. 65:275-283.
SIAU, J. F. (1995). Wood: Influence of Moisture on Physical Properties. Virginia Polytechnic Institute and State University, Keene NY.
SKAAR, C. (1988). Wood-Water Relations. Springer-Verlag Berlin/Heidelberg/New York.
WADSO, L. (1994). Unsteady-State Water Vapor Adsorption In Wood: An Experimental Study. Wood Fiber Sci 26(1):36-50
WATANABE, K., SAITO, Y., AVRAMIDIS, S., SHIDA, S. (2008). Non-Destructive Measurement Of Moisture Distribution In Wood During Drying Using Digital X-Ray Microscopy. Drying Techn. 26:590-595.
WIBERG P., MOREN T.J. (1999). Moisture Flux Determination in Wood During Drying Above Fibre Saturation Point Using CT-Scanning and Digital Image Processing. Holz Roh- Werkst. 57:137-144.
ZILLIG, W., DEROME, D., DIEPENS, J., CARMELIET, J. (2007). Modelling Hysteresis of Wood. Proceedings of the 12th Symposium for Building Physics, 29th to 31st March 2007, Dresden.