Springer Berlin Heidelberg
Berlin/Heidelberg
Springer
226
10.1007/226.1432-5225
0043-7719
1432-5225
Wood Science and Technology
Journal of the International Academy of Wood Science
Wood Sci Technol
Life Sciences
Wood Science & Technology
Ceramics, Glass, Composites, Natural Materials
Operating Procedures, Materials Treatment
Biomedical and Life Sciences
52
52
6
3
3
17
2018
4
13
2018
4
13
2018
5
2018
Springer-Verlag GmbH Germany, part of Springer Nature
2018
993
10.1007/s00226-018-0993-2
12
Rheological behavior of wood in stress relaxation under compression
Original
793
808
2018
2
3
2017
10
4
2018
2
9
The Author(s)
2018
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Sabina
Huč
sabina.huc@hb.se
Tomaž
Hozjan
Staffan
Svensson
0000 0000 9477 7523
grid.412442.5
Faculty of Textiles, Engineering and Business
University of Borås
501 90
Borås
Sweden
0000 0004 1936 9457
grid.8993.b
Ångström Laboratory, Division of Applied Mechanics
Uppsala University
751 21
Uppsala
Sweden
0000 0001 0721 6013
grid.8954.0
Faculty of Civil and Geodetic Engineering
University of Ljubljana
1000
Ljubljana
Slovenia
Abstract
Rheological behavior of wood under uniaxial compression along and perpendicular to the grain in constant environment was examined. Tests with constant deformation rate until failure and stress relaxation tests with constant deformation applied stepwise were carried out. The experimental results of stress relaxation showed nonlinear material behavior over time that got more prominent under high deformation levels. Considerable amount of stress relaxed during applying the deformation. Wood experienced greater stress relaxation along the grain than perpendicular to it. Three rheological models for orthotropic material were calibrated to the experimentally determined stress–time curves in longitudinal and transverse directions simultaneously. Small deformation levels assuming linear strains were accounted for in the models. Required elastic material parameters were determined from the tests with constant deformation rate. A model including the highest number of viscoelastic material parameters was the most successful in predicting stress relaxation of wood under stepwise deformation. Modeling indicated that wood behavior was very close to linear viscoelastic in relaxation under small deformation. The obtained material parameters made the model suitable for predicting rheological behavior of wood comprehensively, under sustained deformation or load in constant conditions.
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