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A global rheological model of wood cantilever as applied to wood drying

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Abstract

In the process of wood drying inevitable stresses are induced. This often leads to checking and undesired deformations that may greatly affect the quality of the dried product. The purpose of this study was to propose a new rheological model representation capable to predict the evolution of stresses and deformations in wood cantilever as applied to wood drying. The rheological model considers wood shrinkage, instantaneous stress–strain relationships, time induced creep, and mechano-sorptive creep. The constitutive law is based on an elasto–viscoplastic model that takes into account the moisture content gradient in wood, the effect of external load, and a threshold viscoplastic (permanent) strain which is dependent on stress level and time. The model was implemented into a numerical program that computes stresses and strains of wood cantilever under constant load for various moisture content conditions. The results indicate that linear and nonlinear creep behavior of wood cantilever under various load levels can be simulated using only one Kelvin element model in combination with a threshold-type viscoplastic element. The proposed rheological model was first developed for the identification of model parameters from cantilever creep tests, but it can be easily used to simulate drying stresses of a piece of wood subjected to no external load. It can therefore predict the stress reversal phenomenon, residual stresses and maximum stress through thickness during a typical drying process.

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Acknowledgments

The authors are grateful for the financial support of this research from Natural Sciences and Engineering Research Council of Canada (No. 224297) and Forintek Canada Corp.

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Authors and Affiliations

  1. Centre de recherche sur le bois (CRB), Département des sciences du bois et de la forêt, Université Laval, Québec, QC, Canada, G1K 7P4

    Mohssine Moutee & Yves Fortin

  2. Département de génie civil, Université Laval, Québec, QC, Canada, G1K 7P4

    Mario Fafard

Authors
  1. Mohssine Moutee
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  2. Yves Fortin
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  3. Mario Fafard
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Correspondence to Yves Fortin.

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Moutee, M., Fortin, Y. & Fafard, M. A global rheological model of wood cantilever as applied to wood drying. Wood Sci Technol 41, 209–234 (2007). https://doi.org/10.1007/s00226-006-0106-5

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  • DOI: https://doi.org/10.1007/s00226-006-0106-5

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