TAILIEUCHUNG - Báo cáo khoa học: "Tree mechanics and wood mechanics: relating hygrothermal recovery of green wood to the maturation process"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài:"Tree mechanics and wood mechanics: relating hygrothermal recovery of green wood to the maturation process. | 329 Ann Sci For 1994 51 329-338 Elsevier INRA Original article Tree mechanics and wood mechanics relating hygrothermal recovery of green wood to the maturation process J Gril B Thibaut Laboratoire de Mécanique et Génie Civil URA 1214 du CNRS University de Montpellier II place Eugène-Bataillon CP 081 34095 Montpellier Cedex 5 France Received 24 December 1992 accepted 13 July 1993 Summary Growth stress can be approached from the point of view of the mechanical standing of trees as well as that of the loading history applied to the material before tree felling. Stress originates in wood maturation causing both rigidification and expansion to the cell-wall material. Locked-in strains are partially released by cutting specimens from the tree and more completely by boiling them in a green state so as to exceed to softening point of lignin. It has been supposed that the rheological conditions during such hygrothermal recovery might be similar to those existing during maturation when lignification of the secondary cell wall occurred. A rheological model of wood in the process of formation is proposed to support this hypothesis and derive information on the average maturation rigidity. wood rheology I viscoelasticity growth stress I hygrothermal recovery cell wall Resume Mécanique de I arbre et mécanique du bois. Relation entre la recouvrance hygro-thermique du bois vert et le processus de maturation. Les contraintes de croissance peuvent être abordées du double point de vue de la tenue mécanique des arbres et de I histoire du chargement appli-qué surle matériau jusqu a I abattage de I arbre. Elies trouvent leur origine dans la maturation du bois qui provoque à la fols la rigidification et expansion de la matière constitutive des parois. Les deformations bloquées sont partiellement relâchées lorsque des échantillons sont extraits de I arbre elles le sont plus complètement si ceux-ci sont chauffes à 1 état vert au-dessus de la temperature de transition de la lignine. On a .

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