TAILIEUCHUNG - Báo cáo lâm nghiệp: "Mesures des déformations bloquées dans un disque de bois vert. Méthode de la fermeture"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế, đề tài:"Mesures des déformations bloquées dans un disque de bois vert. Méthode de la fermeture. | 955 Ann Sci For 1996 53 955-966 Elsevier INRA Article original Mesures des deformations bloquées dans un disque de bois vert. Methode de la fermeture D Jullien J Gril Laboratoire ơe mécanique etgénie civil université de Montpellier-Il cc 81 place Eugène-Batailton 34095 Montpellier cedex 5 France Reẹu to 6 mars 1995 accepté le 12juiltot 1995 Summary - Measurement of locked-in strains in a green crosscut. The closing method. Initiation and propagation of heart checks at log ends after tree felling lead to serious problems for wood exploitation. This phenomenon is caused by the release of strains locked-in during cell maturation and is triggered by steaming its understanding requires an improved knowledge of residual strains in logs particularly transversally to fibers. A procedure completing the longitudinal measurements at tree periphery is presented based on the instantaneous closing of green crosscuts caused by a radial opening followed by the hygrothermal closing provoked by boiling fig 3 . The relative displacement of two pins nailed near periphery is measured using a special device fig 1 and divided by girth to give a global transverse strain p. Local measurements of the radial strain Er and the tangential strain Er performed using the same device fig 2 showed that p partially expressed the strain anisotropy E -Er fig 8 . Instantaneous values of obtained on 132 chestnuts Castanea sativa Mill were weakly correlated to longitudinal strains fig 10 . Hygrothermal strains reached after 30 min at 80 C correctly expressing splitting trends the more wood cracked tangentially the less it did radially the potiential transverse strain remaining for all rupture modes fig 12 . chestnut wood mechanics transverse strain hygrothermal recovery heart check Resume - L apparition et la propagation de fentes radiales en bout de grume suite à I abattage d un arbre entraĩnent de sérieux problèmes pour exploitation du bois. On salt que ce phenomena est provoqué par la .

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