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Numerical study of how creep and progressive stiffening affect the growth stress formation in trees

Ormarsson, Sigurdur; Dahlblom, Ola LU and Johansson, Marie (2010) In Trees 24(1). p.105-115
Abstract
It is not fully understood how much growth stresses affect the final quality of solid timber products in terms of, e.g. shape stability. It is, for example, difficult to predict the internal growth stress field within the tree stem. Growth stresses are progressively generated during the tree growth and they are highly influenced by climate, biologic and material-related factors. To increase the knowledge of the stress formation, a finite element model was created to study how the growth stresses develop during the tree growth. The model is an axisymmetric general plane strain model where material for all new annual rings is progressively added to the tree during the analysis. The material model used is based on the theory of small strains... (More)
It is not fully understood how much growth stresses affect the final quality of solid timber products in terms of, e.g. shape stability. It is, for example, difficult to predict the internal growth stress field within the tree stem. Growth stresses are progressively generated during the tree growth and they are highly influenced by climate, biologic and material-related factors. To increase the knowledge of the stress formation, a finite element model was created to study how the growth stresses develop during the tree growth. The model is an axisymmetric general plane strain model where material for all new annual rings is progressively added to the tree during the analysis. The material model used is based on the theory of small strains (where strains refer to the undeformed configuration which is good approximation for strains less than 4%) where so-called biological maturation strains (growth-related strains that form in the wood fibres during their maturation) are used as a driver for the stress generation. It is formulated as an incremental material model that takes into account elastic strain, maturation strain, viscoelastic strain and progressive stiffening of the wood material. The results clearly show how the growth stresses are progressively generated during the tree growth. The inner core becomes more and more compressed, whereas the outer sapwood is subjected to slightly increased tension. The parametric study shows that the growth stresses are highly influenced by the creep behaviour and evolution of parameters such as modulus of elasticity, micro-fibril angle and maturation strain. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Creep, Wood, Finite element simulations, Growth stresses, Trees, Distortions
in
Trees
volume
24
issue
1
pages
105 - 115
publisher
Springer
external identifiers
  • wos:000273481700011
  • scopus:73649091723
ISSN
1432-2285
DOI
10.1007/s00468-009-0383-3
language
English
LU publication?
yes
id
a9233af6-5ef0-46d7-a33f-353a29c4fbb5 (old id 1547446)
date added to LUP
2010-02-23 14:08:26
date last changed
2018-09-30 03:45:15
@article{a9233af6-5ef0-46d7-a33f-353a29c4fbb5,
  abstract     = {It is not fully understood how much growth stresses affect the final quality of solid timber products in terms of, e.g. shape stability. It is, for example, difficult to predict the internal growth stress field within the tree stem. Growth stresses are progressively generated during the tree growth and they are highly influenced by climate, biologic and material-related factors. To increase the knowledge of the stress formation, a finite element model was created to study how the growth stresses develop during the tree growth. The model is an axisymmetric general plane strain model where material for all new annual rings is progressively added to the tree during the analysis. The material model used is based on the theory of small strains (where strains refer to the undeformed configuration which is good approximation for strains less than 4%) where so-called biological maturation strains (growth-related strains that form in the wood fibres during their maturation) are used as a driver for the stress generation. It is formulated as an incremental material model that takes into account elastic strain, maturation strain, viscoelastic strain and progressive stiffening of the wood material. The results clearly show how the growth stresses are progressively generated during the tree growth. The inner core becomes more and more compressed, whereas the outer sapwood is subjected to slightly increased tension. The parametric study shows that the growth stresses are highly influenced by the creep behaviour and evolution of parameters such as modulus of elasticity, micro-fibril angle and maturation strain.},
  author       = {Ormarsson, Sigurdur and Dahlblom, Ola and Johansson, Marie},
  issn         = {1432-2285},
  keyword      = {Creep,Wood,Finite element simulations,Growth stresses,Trees,Distortions},
  language     = {eng},
  number       = {1},
  pages        = {105--115},
  publisher    = {Springer},
  series       = {Trees},
  title        = {Numerical study of how creep and progressive stiffening affect the growth stress formation in trees},
  url          = {http://dx.doi.org/10.1007/s00468-009-0383-3},
  volume       = {24},
  year         = {2010},
}