European Journal of Wood and Wood Products

, Volume 73, Issue 1, pp 17–27 | Cite as

Local variation of modulus of elasticity in timber determined on the basis of non-contact deformation measurement and scanned fibre orientation

  • Min HuEmail author
  • Marie Johansson
  • Anders Olsson
  • Jan Oscarsson
  • Bertil Enquist


During the last decade, the utilization of non-contact deformation measurement systems based on digital image correlation (DIC) has increased in wood related research. By measuring deformations with DIC systems, surface strain fields can be calculated. The first aim of this study concerns the possibility to detect detailed strain fields along the entire length of a wooden board subjected to pure bending and the potential of using such strain fields to determine a bending modulus of elasticity (MOE) profile along a board. Displacements were measured over 12 subareas along a flat surface of the board. For each such area, a separate local coordinate system was defined. After the transformation of locally measured coordinates to a global system, high resolution strain fields and a corresponding bending MOE profile were calculated. A second method in establishing bending MOE profiles is to use fibre angle information obtained from laser scanning and a calculation model based on integration of bending stiffness over board cross sections. Such profiles have recently been utilized for accurate strength grading. A second aim of this study was to investigate the accuracy of the bending MOE profiles determined using the latter method involving fibre angle information. Bending MOE profiles determined using the two described methods agree rather well. However, for some patterns of knot clusters, the local bending MOE, calculated on the basis of fibre angles and integration of bending stiffness, is overestimated. Hence, this research adds knowledge that may be utilized to improve the newly suggested strength grading method.


Digital Image Correlation Fibre Orientation Wood Surface Fibre Angle Load Stage 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols


MOE in the local longitudinal fibre direction


MOE in the global x-direction, i.e. the direction of the board


Average bending MOE over cross-sections along the global x-direction, also referred to as bending MOE


Bending stiffness over cross sections with respect to the global z-direction


Normal strain in the global x-direction


Normal strain in the global y-direction


Shear strain in the global xy-plane


Conflict of interest

The authors declare that they have no conflict of interest.


  1. Hu M, Johansson M, Olsson A, Bengtsson C, Brandt A (2011) Grading of sawn timber using the vibration technique—locating imperfections based on flexural mode shapes. In: Divos F Proceedings of the 17th international nondestructive testing and evaluation of wood symposium, 1, University of West Hungary, Sopron Hungary, September 14–16, pp 269–276Google Scholar
  2. Lundström T, Heiz U, Stoffel M, Stöckli V (2007) Fresh-wood bending: linking the mechanical and growth properties of a Norway spruce stem. Tree Physiol 27(9):1229–1241PubMedCrossRefGoogle Scholar
  3. GOM mbH (2007) ARAMIS user manual—software, version 6.1Google Scholar
  4. Nyström J (2003) Automatic measurement of fibre orientation in softwoods by using the tracheid effect. Comput Electron Agric 41(1):91–99CrossRefGoogle Scholar
  5. Olsson A, Oscarsson J, Serrano E, Källsner B, Johansson M, Enquist B (2013) Prediction of timber bending strength and in-member cross-sectional stiffness variation on the basis of local wood fibre orientation. Eur J Wood Prod 71(3):319–333CrossRefGoogle Scholar
  6. Orosz I (1976) Relationship between apparent modulus of elasticity, gauge length, and tensile strength of timber. Wood Sci Technol 10(4):273–291Google Scholar
  7. Oscarsson J (2014) Strength grading of structural timber and EWP laminations of Norway spruce—development potentials and industrial applications. Doctoral dissertation, Department of Building Technology, ISBN: 978-91-87427-84-8, Linnaeus University, Växjö, SwedenGoogle Scholar
  8. Petersson H (2010) Use of optical and laser scanning techniques as tools for obtaining improved FE-input data for strength and shape stability analysis of wood and timber. In: Proceedings of the IV European conference on computational mechanics, Paris, May 16–21Google Scholar
  9. Sjödin J, Serrano E, Enquist B (2006) Contact-free measurements and numerical analyses of the strain distribution in the joint area of steel-to-timber dowel joints. Holz Roh Werkst 64:497–506CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Min Hu
    • 1
    Email author
  • Marie Johansson
    • 1
  • Anders Olsson
    • 1
  • Jan Oscarsson
    • 2
  • Bertil Enquist
    • 1
  1. 1.Department of Building TechnologyLinnaeus UniversityVäxjöSweden
  2. 2.SP Wood Technology, SP Technical Research Institute of SwedenVäxjöSweden

Personalised recommendations