TAILIEUCHUNG - Báo cáo lâm nghiệp: "Reduction of wood hygroscopicity and associated dimensional response by repeated humidity cycles"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài:"Reduction of wood hygroscopicity and associated dimensional response by repeated humidity cycles" | Ann. For. Sci. 62 2005 275-284 INRA EDP Sciences 2005 DOI forest 2005020 275 Original article Reduction of wood hygroscopicity and associated dimensional response by repeated humidity cycles Luis García EsTEBANa Joseph GRiLb Paloma DE Palacios de PALACiosa Antonio Guindeo CASASÚSa a Cátedra de Tecnología de la Madera Departamento de Ingeniería Forestal Escuela Técnica Superior de Ingenieros de Montes Universidad Politécnica de Madrid Ciudad Universitaria s n 28040 Madrid Spain b Laboratoire de Mécanique et Génie Civil Université Montpellier 2 France Received 14 April 2003 accepted 31 August 2004 Abstract - The reduction of wood response to variations of ambient humidity described as kind of ageing has been studied from both points of view of moisture uptake and dimensional changes. Clearwood specimens from 3 gymnosperms Pinus sylvestris L. Pinus pinaster Ait. Pinus insignis Dougl. and 4 angiosperms Populus spp. Quercuspyrenaica Willd. Entandrophragma cylindricum Sprague Chlorophora excelsa Benth. Hook f. were subjected to five wet-dry cycles and their moisture content and dimensional changes in radial and tangential direction at three increasing levels of relative humidity and were measured before and after the treatment. For a given increase of relative humidity a coefficient of hygroscopic ageing was defined as the relative decrease of moisture uptake and the coefficient of dimensional ageing as the difference of swelling strain before and after ageing. All species exhibited a clear ageing effect much stronger in the wet range than in the dry range. Calculation of swelling coefficients suggested that in some cases the relation between swelling strain and moisture content is no longer linear in aged wood. wood sorption hygroscopicity swelling ageing Résumé - Reduction de l hygroscopicite du bois et des variations dimensionnelles associées au moyen de cycles d humidite répétés. La reduction de la réponse du bois aux variations d humidité .

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