Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài:" Viscoelastic behaviour of green wood across the grain. Part I. Thermally activated creep tests up to 120 °C" | Ann. For. Sci. 62 2005 707-716 INRA EDP Sciences 2005 DOI forest 2005067 707 Original article Viscoelastic behaviour of green wood across the grain. Part I. Thermally activated creep tests up to 120 C Joelle Passard Patrick PERRÉ Laboratory of Wood Science LERMAB UMR 1093 INRA ENGREF Université H. Poincaré Nancy 1 ENGREF 14 rue Girardet 54042 Nancy Cedex France Received 31 July 2004 accepted 31 May 2005 Abstract - In this work we present an improved experimental set-up capable of performing creep tests on water-saturated samples up to 120 C. A typical test consists of three phases a linear increase in temperature up to the desired value a plateau at this temperature level during 15 h and a cooling period. For each species spruce and oak and each direction across the grain radial and tangential a whole set of creep tests is available at different plateau temperatures 65 C 85 C 105 C and 120 C. The modulus of elasticity MOE measured at room temperature on green wood confirms expected results it is almost twice as high in radial direction and more than twice as high for oak average values of 253 and 119 MPa for Spruce and 687 and 398 MPa for Oak in radial and tangential direction respectively. In the case of oak the MOE of tension wood can also be distinguished from normal wood its modulus is smaller in spite of a higher density. The creep tests reveal the importance of the temperature level on the thermal activation the apparent MOE might loss more than two orders of magnitude after a test at 120 C. This effect is more pronounced and starts at lower temperature values for oak than for spruce while its is almost the same in relative value in radial and tangential directions. wood viscoelastic Kelvin s element thermal activation model identification inverse method Résumé - Comportement viscoélastique du bois vert dans le plan transverse. Partie I tests de fluage thermo-activés jusqu a 120 C. Dans ce travail nous présentons un dispositif amélioré permettant d .
