Research Output

The non-destructive evaluation of Sitka spruce mechanical properties using acoustic methods.

  The need for improved timber grading is key to improving Scottish forestry: the
majority (80%) of the sustainable softwood population in Scotland is Sitka spruce
of variable quality. Current visual assessment of strength and stiffness is
inaccurate, and machine stress grading in sawmills is little better due to incorrect
assumptions regarding consistency within softwood species and between trees of
the same stand. The author develops and evaluates non-destructive test (NOT)
methods for Scottish Sitka spruce based upon impact-e9ho testing across a range
of scales from plank, to log, to standing tree.
Correlations between harmonic wave propagation velocity and elastic modulus of
0.62 ::; R2 ::; 0.71 were possible in Sitka spruce under a range of conditions
including: genotype progeny, variable height and radial position in stem, and
variable knot content. In achieving this correlation, the research also investigated
acoustic parameters such as: time of flight velocity, damping ratio, and resonant
peak behaviour with regard to their influence on dynamically derived moduli of
elasticity. Examination of variation in wood properties (including static elastic
modulus, knot content, simulated decay, density, and grain alignment) on these
acoustic parameters was conducted on semi-controlled specimens of differing
homogeneities. The consequences of these results should influence the
development of timber NOT tools.
In addition to the development of an NOT method, the author has provided the first
large-scale derivation of reference values for dynamic stiffness and other acoustic
properties for 35 year old logs and beams of Sitka spruce in Scotland.

  • Type:

    Thesis

  • Date:

    31 May 2009

  • Publication Status:

    Unpublished

  • Library of Congress:

    TH Building construction

  • Dewey Decimal Classification:

    674 Lumber processing, wood products & cork

Citation

MacKenzie, R. The non-destructive evaluation of Sitka spruce mechanical properties using acoustic methods. (Thesis)

Keywords

Scottish forestry; timber grading; Sitka spruce; sustainability; non-destructive test (NDT);

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