lnu.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • 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
Three-dimensional orthotropic nonlinear transient moisture simulation for wood: analysis on the effect of scanning curves and nonlinearity
Linnaeus University, Faculty of Technology, Department of Building Technology.ORCID iD: 0000-0001-7322-7052
Linnaeus University, Faculty of Technology, Department of Building Technology.ORCID iD: 0000-0003-1638-1023
Linnaeus University, Faculty of Technology, Department of Building Technology.ORCID iD: 0000-0003-4054-462X
Linnaeus University, Faculty of Technology, Department of Building Technology.ORCID iD: 0000-0001-5591-1045
2020 (English)In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 54, p. 1197-1222Article in journal (Refereed) Published
Abstract [en]

This paper introduces, with the development of user-subroutines in the finite-element software Abaqus FEA (R), a new practical analysis tool to simulate transient nonlinear moisture transport in wood. The tool is used to revisit the calibration of moisture simulations prior to the simulation of mechanical behaviour in bending subjected to climate change. Often, this calibration does not receive sufficient attention, since the properties and mechanical behaviour are strongly moisture dependent. The calibration of the moisture transport simulation is made with the average volumetric mass data experimentally obtained on a paired specimen of Norway spruce (Picea abies) with the dimensions 30x15x640 mm(3). The data, from a 90-day period, were measured under a constant temperature of 60 degrees C and systematic relative humidity cycles between 40 and 80%. A practical method based on analytical expressions was used to incorporate hysteresis and scanning behaviour at the boundary surface. The simulation tool makes the single-Fickian model and Neumann boundary condition readily available and the simulations more flexible to different uses. It also allows for a smoother description of inhomogeneity of material. The analysis from the calibration showed that scanning curves associated with hysteresis cannot be neglected in the simulation. The nonlinearity of the analysis indicated that a coherent set of moisture dependent diffusion and surface emission coefficient is necessary for the correct description of moisture gradients and mass transport.

Place, publisher, year, edition, pages
Springer, 2020. Vol. 54, p. 1197-1222
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
URN: urn:nbn:se:lnu:diva-98160DOI: 10.1007/s00226-020-01210-4ISI: 000559655700001Scopus ID: 2-s2.0-85089399972OAI: oai:DiVA.org:lnu-98160DiVA, id: diva2:1470459
Available from: 2020-09-24 Created: 2020-09-24 Last updated: 2024-06-17Bibliographically approved
In thesis
1. Moisture-induced stress and distortion of wood: A numerical and experimental study of wood's drying and long-term behaviour
Open this publication in new window or tab >>Moisture-induced stress and distortion of wood: A numerical and experimental study of wood's drying and long-term behaviour
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

With the current advances made in three-dimensional modelling of wood, it is possible to provide an overall picture of moisture flow, and moisture-induced stress and deformations, whereas previously, experiments only provided local measurements. The main aim of the doctoral thesis is to investigate the possibilities of the developed three-dimensional numerical model to predict the behaviour of wood when simultaneously exposed to a mechanical load and a particular climate. Three applications in the fields of wood drying and long-term behaviour of wood are considered: 1) the effect of green-state moisture content on the drying behaviour of timber boards, 2) the calibration of the numerical model based on a long-term four-point bending tests using small wood beams subjected to a constant temperature and systematic relative humidity (RH) changes, and 3) the validation of the numerical model by means of a long-term four-point bending test on solid timber beams subjected to Northern European climate. As part of the second application, an experimental methodology and analytical method were designed. The numerical model was developed in finite element software Abaqus FEA® and consists of several user-subroutines to include material orientation (i.e. annual ring pattern, conical shape and spiral grain), and the selected constitutive behaviour and required boundary conditions. To simulate the moisture flow, a nonlinear single-Fickian approach was combined with a nonlinear Neumann boundary condition, which describes the flux normal to the exchange surface based on a moisture and temperature dependent surface emission coefficient. A strain relation was used that accounts for hygro-expansion, and the elastic, creep and mechano-sorptive behaviour. The analytical method describes the elastic and creep deflection in the constant moment area of the four-point bending setup, and was used to isolate and assess the mechano-sorption deflection in the cumulative moisture content domain. The results show that the three-dimensional character of the numerical model contributed to the analysis and visualisation of the different stress states and deformations that are affected by material properties that vary (i.e. from pith to bark, between heartwood and sapwood, and due to temperature and moisture content), fibre orientation and climate. The simulations made on timber boards clarified phenomena, such as stress reversal and casehardening associated with wood drying, and showed that the green-state moisture content affected the time, size and frequency with which extremes in tangential tensile stress developed inside the timber during drying. The results of the calibration and validation indicated that the numerical model is able to describe moisture change and gradients in the considered temperature and relative humidity ranges (between -2-60℃ and 40-80% RH), as well as the deflection. The experimental methodology and analytical method led to a successful identification of each deflection component and isolation of the mechano-sorptive deflection curves. The experimental methodology benefitted the calibration of the numerical model. In conclusion, the presented three-dimensional numerical model compatible with Abaqus FEA® provides a powerful tool for scientists and timber engineers to study the combined effect of load and climate on stress state and deformations of various timber products in a wide field of applications.

Place, publisher, year, edition, pages
Växjö: Linnaeus University Press, 2021. p. 198
Series
Linnaeus University Dissertations ; 407
Keywords
analytical method, calibration, controlled climate, creep, distortion, experimental methodology, FEM, fibre orientation, mechano-sorption, moisture transport, natural climate, Norway spruce, numerical model, three-dimensional, timber beam, validation, wood
National Category
Wood Science Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering; Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-101602 (URN)9789189283435 (ISBN)9789189283442 (ISBN)
Public defence
2021-03-04, N1017, Hus N, Växjö, 10:00 (English)
Opponent
Supervisors
Available from: 2021-03-15 Created: 2021-03-13 Last updated: 2024-03-04Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textScopus

Authority records

Florisson, SaraVessby, JohanMmari, WinstonOrmarsson, Sigurdur

Search in DiVA

By author/editor
Florisson, SaraVessby, JohanMmari, WinstonOrmarsson, Sigurdur
By organisation
Department of Building Technology
In the same journal
Wood Science and Technology
Wood Science

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 295 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • 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