Abstract
Wood specimens have been tested for compressive loading in the longitudinal direction. Planar deformation was recorded by means of video extensometry on the specimen surfaces. A post processing routine was developed to calculate stress and strain values from the sampled data. The routine made use of mathematical framework used in the finite element method. Material parameters were detected by means of an optimization algorithm, and the determined linear elastic parameters were in general found to be in good agreement with values given in literature. The utilized method offers simultaneous average values for active, passive and shear strains from the measured area. Moduli of elasticity, Poisson’s ratios and shear deformation can thus be evaluated. In addition, the variation of the three strain components over the area is measured. The results can therefore be used for quantification of material inhomogeneity and are further suitable for direct comparison with numerically computed strains comprising non-uniform strain fields. Since video extensometry does not require any physical contact with the specimen, measurements can be undertaken until failure. The present method offers thus an efficient and relatively accurate way to measure and evaluate the material characteristics of anisotropic and inhomogeneous materials like wood.
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References
Choi D, Thorpe JL, Hanna RB (1991) Image analysis to measure strain in wood and paper. Wood Sci Technol 25:251–262
Reiterer A, Stanzl-Tschegg SE (2001) Compressive behaviour of softwood under uniaxial loading at different orientations to the grain. Mech Mater 33:705–715. doi:10.1016/S0167-6636(01)00086-2
Ukyo S, Masuda M (2004) Investigation of the true stress–strain relation in shear using the digital image correlation method. Journal of Wood Science-Official Journal of the Japan Wood Research Society 50(3):146–150
Ukyo S, Masuda M (2006) A new method for measuring the true shear strength of wood. 9th World Conference on Timber Engineering, Portland USA
Sinha A, Gupta R, Muszyński L (2006) Strain profile in wood frame shear walls—preliminary results. 9th World Conference on Timber Engineering, Portland USA
Franke S, Franke B, Ratuenstrauch K (2007) Strain analysis of wood components by close range photogrammetry. Mat Struct 40:37–46
European Committee for Standardization NSF (2003) NS-EN 338 Structural timber strength classes, 2nd edn. p 7
European Committee for Standardization NSF (2003) NS-EN 408 Timber structures–structural timber and glued laminated timber. Determination of some physical and mechanical properties, 2nd edn. p 27
Dinwoodie JM (2000) Timber. Its nature and behaviour, 2nd edn. E & FN SPON, London, p 257
Dept. of Forestry, Agricultural University of Norway SKOGFORSK (1992) Skandinaviske normer for testing av små feilfrie prøver av heltre, SKANORM, p 104
Sunde FF (2005) Strength properties of small, clear wood specimens of Norway spruce (in Norwegian). Institutt for naturforvaltning, Norwegian University of Life Sciences. Master thesis, p 53
Minitab (2006) Minitab help. Minitab Inc. Statistical Software, State College, Pennsylvania
Larsen RJ, Marx ML (1990) Statistics. Prentice-Hall Inc., New Jersey, p 829
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Dahl, K.B., Malo, K.A. Planar Strain Measurements on Wood Specimens. Exp Mech 49, 575–586 (2009). https://doi.org/10.1007/s11340-008-9162-0
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DOI: https://doi.org/10.1007/s11340-008-9162-0