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Modelling of growth stress generation and timber distortions related to log sawing and forced drying
Technical University of Denmark, Denmark.ORCID iD: 0000-0001-5591-1045
Lund University, Sweden.
2008 (English)In: 8th World Congress on Computational Mechanics and 5th European Congress on Computational Methods in Applied Sciences and Engineering, 2008Conference paper, Published paper (Refereed)
Abstract [en]

Growth stresses can cause fibre collapse in living trees (often in combination with strong wind loading), internal checking resulting in end-splitting of logs, and instantaneous board distortions when the log is split into timber. How much the growth rate and growth stresses affect the final shape stability of solid timber products is not fully understood. For trees with abnormal growth conditions resulting in eccentric growth and generation of reaction wood, it is very complicated to estimate how timber products made of such material will behave during moisture variation. To study this behaviour a finite element analysis in which stress formation during normal and abnormal tree growth was simulated with the aim of better understanding of the growth stress formation.

The model for progressive growth stress generation in trees with normal growth conditions is formulated as a one dimensional axisymmetric general plane strain model of the tree stem. The trunk is considered as a very long solid cone with zero shear stresses. In the model, each new (and stress free) annual ring is progressively added to the stem during the analysis. Thereafter the cell maturation is assumed to start, i.e. the crystallization of the cellulose leads to longitudinal shrinkage of the new annual ring whereas the lignification process results in transversal expansion of the fibres. Since the maturing annual ring is attached to the old and already matured rings, a strain constraint develops in the stem. The new annual ring becomes stretched longitudinally and compressed tangentially, whereas the matured rings are exposed to the opposite stress conditions. The material model used is based on the assumption of small strains and the biological maturation strains are used as a driving force for the growth stress evolutions. The aim here is also to take into account viscous effects of the wood material. ......

Place, publisher, year, edition, pages
2008.
Keyword [en]
Growth Stress, Board Distortion, Wood, Numerical Simulation.
National Category
Engineering and Technology Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
URN: urn:nbn:se:lnu:diva-41207OAI: oai:DiVA.org:lnu-41207DiVA: diva2:800327
Conference
8th World Congress on Computational Mechanics and 5th European Congress on Computational Methods in Applied Sciences and Engineering,June 30 – July 5, 2008 Venice, Italy
Note

Ej belagd 20150820

Available from: 2015-04-02 Created: 2015-03-22 Last updated: 2016-05-03Bibliographically approved

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CiteExportLink to record
Permanent link

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Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf