Mechanics of Time-Dependent Materials

, Volume 9, Issue 4, pp 1–21 | Cite as

Three Dimensional Creep Model for Wood Under Variable Humidity-Numerical Analyses at Different Material Scales

  • P. Chassagne
  • E. Bou Saïd
  • J. F. Jullien
  • P. Galimard
Article

Abstract

This paper presents a qualitative explanation of the creep phenomenon based on the physical and chemical mechanisms that occur at micro and ultra-structural levels of wood during moisture diffusion. This part is then completed by the formulation of a 3-dimensional non linear hydro-visco-elastic model, combined with hygro-expansion effects, and able to describe creep and recovery phenomena under variable humidity conditions. The constitutive relation is based on a generalised Maxwell model whose relaxation time functions depend on the moisture content rate, the history of accumulated moisture variations and the stress level. The model was implemented in a Finite Element (FE) program. Several applications based on external experimental tests and with creep periods ranging from 1 to 2735 days were carried out in order to prove the relevance of the approach at different structure scales. A local strain energy density criterion, associated with a flow law, allows the representation of the rupture phase initiated by the tertiary creep and is incorporated into the model in order to open up new horizons for the service life estimation of timber structures.

Key words

wood material Finite Element Method rheological model delayed deformations mechanosorption failure criterion inverse parameters identification multi-scale validations 

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Copyright information

© Springer Science + Business Media, Inc. 2006

Authors and Affiliations

  • P. Chassagne
    • 1
  • E. Bou Saïd
    • 1
  • J. F. Jullien
    • 1
  • P. Galimard
    • 2
  1. 1.Laboratory of Contact and Solid MechanicsINSA LyonVilleurbanne CedexFrance
  2. 2.Laboratory of Wood Rheology of BordeauxCestas GazinetFrance

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