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Journal of Wood Science

Official Journal of the Japan Wood Research Society

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Strain analysis of lumber containing a knot during tensile failure

Journal of Wood Science volume 57, pages 114–118 (2011)Cite this article

Abstract

We analyzed the strain distribution of lumber containing a knot under a tensile load. The local tensile strain near the knot was measured using the digital image correlation method. Fracture often initiated near the knot where the fiber orientation changed in a three-dimensional manner. The fiber direction in this zone was different from that in the clear part, coinciding with the thickness direction and not with the longitudinal direction of the specimen. Our results disagree with those of previous models that assumed the longitudinal direction of lumber as the direction of crack propagation. Strain analysis showed that a nonlinear region existed around the knot just before ultimate fracture occurred. The results indicated that nonlinear characterization is necessary to determine the failure mechanism of lumber containing a knot, despite the brittleness fracture at the macroscopic scale.

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Authors and Affiliations

  1. Division of Forest and Biomaterials Science, Graduate School of Agriculture, Kyoto University, Kitashirakawa, Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan

    Hiroaki Nagai, Koji Murata & Takato Nakano

Authors
  1. Hiroaki Nagai
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  2. Koji Murata
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  3. Takato Nakano
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Correspondence to Hiroaki Nagai.

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Nagai, H., Murata, K. & Nakano, T. Strain analysis of lumber containing a knot during tensile failure. J Wood Sci 57, 114–118 (2011). https://doi.org/10.1007/s10086-010-1154-x

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  • DOI: https://doi.org/10.1007/s10086-010-1154-x

Key words

  • Strain distribution analysis
  • Knot
  • Digital image correlation