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Representation of the linear viscoelastic behaviour of wood with a constitutive theory based on fractional time derivatives
Author(s) -
Ranz T.,
Lion A.
Publication year - 2007
Publication title -
pamm
Language(s) - English
Resource type - Journals
ISSN - 1617-7061
DOI - 10.1002/pamm.200700925
Subject(s) - viscoelasticity , creep , rheology , anisotropy , fractional calculus , constitutive equation , kelvin–voigt material , representation (politics) , materials science , phenomenological model , mechanics , mathematics , mathematical analysis , physics , composite material , thermodynamics , optics , statistics , finite element method , politics , political science , law
Like many other materials used in mechanical and civil engineering, wood shows a pronounced history‐dependent mechanical material behaviour. Due to its anisotropy its rheological behaviour is strongly dependent on the direction. In this research project, the material behaviour is represented with a phenomenological theory of anisotropic fractional viscoelasticity. In order to identify the material functions and parameters, the time‐dependent creep compliances are measured in three orthogonal directions under tension and shear. As a result of the developed constitutive approach, the experimentally observed creep data is described by several power functions. In the second part of the presentation, some differences between classical models of viscoelasticity which are based on Kelvin‐Voigt or Maxwell elements and the fractional approach are presented. The assets and drawbacks with respect to wood are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)