Quantification of knots in dimension lumber using a single-pass X-ray radiation

Oh, Jung-Kwon; Shim, Kug-Bo; Kim, Kwang-Mo; Lee, Jun-Jae

doi:10.1007/s10086-009-1031-7

Cited by 17 publications

(13 citation statements)

References 5 publications

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“…With its help, it is possible to estimate the knots depth ratio (KDR), which represents the local knot thickness divided by the board's one (Oh et al 2009). A first image processing step is used to separate knotty areas to clear wood ones, and the average clear wood density (ρ CW ) can consequently be determined.…”

Section: Samples Description and Destructive Testsmentioning

confidence: 99%

“…A first image processing step is used to separate knotty areas to clear wood ones, and the average clear wood density (ρ CW ) can consequently be determined. For each board, it was assumed that knots density (ρ KN ) is constant and proportional to ρ CW (Oh et al 2009). Finally, the local KDR value is defined by the Equation 4, and will be later used in our strength grading model.…”

Section: Samples Description and Destructive Testsmentioning

confidence: 99%

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Improving strength grading of timber by grain angle measurement and mechanical modeling

Viguier

Jehl

Collet

et al. 2014

Wood Material Science & Engineering

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Timber strength grading has become a major issue in the European Union during the last years, due to the introduction of the Eurocode 5 and all its related standards. Currently, the most performing strength grading machines are able to locally detect the boards' knots sizes and positions and interpret this information through adapted grading models. The best lead to improve their accuracy seems to be the introduction of new information about the boards and adapt the mechanical model to take them in account. Small grain angle causes high reduction of clear wood's mechanical properties; local value of slope of grain appears to be of high interest. The aim of this study is to quantify the additional accuracy that grain angle information can bring to an optical scanner used as a strength grading machine. A specific grading model has been developed accordingly, and the results obtained for different machine/model/loading combinations are presented. These results show that slope of grain measurement can significantly improve the accuracy of the optical scanner, for both modulus of elasticity and modulus of rupture estimations.

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Section: Samples Description and Destructive Testsmentioning

confidence: 99%

Section: Samples Description and Destructive Testsmentioning

confidence: 99%

Improving strength grading of timber by grain angle measurement and mechanical modeling

Viguier

Jehl

Collet

et al. 2014

Wood Material Science & Engineering

View full text Add to dashboard Cite

show abstract

“…However, wood presents significant variability in terms of its mechanical properties, mainly due to factors such as wood species, tree growth rate, density, local singularities (knots, cracks, slope of grain), etc. Machines can be used to perform the mechanical grading of wood, in accordance with the relevant European standards [2][3][4][5].Wood grading machines are based on various principles, such as density measurement, vibrational measurement of the MOE [6][7][8] or singularity detection using optical means, X-rays, or scattering measurement techniques [9][10][11]. To predict bending strength, most of these grading techniques are extremely dependent on the correlation between the MOR and the density or the MOE, and thus only partially take into account local singularities.…”

Section: Introductionmentioning

confidence: 99%

Automatic measurement of wood fiber orientation and knot detection using an optical system based on heating conduction

Daval¹,

Pot²,

Belkacemi³

et al. 2015

Opt. Express

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. Abstract:In this paper, a new approach to computing the deviation of wood grain is proposed. To do this, the thermal conduction properties of timber are used (higher conduction in the fiber direction). Exciting the surface of the wood with a laser and capturing the thermal conduction using a thermal camera, an ellipse can be observed. Using a method similar to the tracheid effect, it is possible to extract information from this ellipse, such as the slope of grain and the presence of knots. With this method it is therefore possible to extend the mechanical model (assessing the mechanical properties of timber) to take certain singularities into account. Using this approach, the slope of grain can be estimated for any wood species, either hardwood or softwood, which was not possible with the existing tracheid effect. References and links

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“…As a result, clear heartwood resulted a 30% heavier than clear sapwood; and differences between wood with defects were even higher (45%). In addition to heartwood formation, the observed higher presence of defects in heartwood, knots particularly, may also contribute to explain such differences (Oh et al, 2009); including a higher presence of compression wood that is formed around knots (e.g. Bengtsson, 2000).…”

Section: Resultsmentioning

confidence: 99%

Physico-mechanical properties of Spanish juniper wood considering the effect of heartwood formation and the presence of defects and imperfections

et al. 2014

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Aim of study: Determining the main physical and mechanical properties of Spanish juniper wood from Soria (Spain) considering the effects of heartwood formation and the presence of defects and imperfections; and comparing the resulting characteristics with similar existing data for other regional softwood species of commercial interest. Area of study: Berlanga de Duero (Soria, Castilla y León), Spain.Material and Methods: Wood physico-mechanical performance was determined by Spanish UNE standards in order to provide proper comparisons to other regional softwood species. An individual tree representing average plot characteristics was selected in all eight 10 m radius circular plots that were established well-representing the heterogeneity of this woodland. The age of every tree was determined reading the number of growth rings at the base of each sampled tree. Every physico-mechanical property was assessed at least 4 times for every wood sample type (sapwood and heartwood, whether clear or with the presence of defects) of each tree. Two-way ANOVA was run to assess significant differences in the results. Post hoc all pairwise comparisons were performed using Tukey's test (p < 0.05).Research highlights: Spanish juniper wood resulted harder than other regional commercial conifers, and showed semi-heavyweight heartwood and lightweight sapwood; whereas shrinkage figures remarked its great dimensional stability. The high presence of knots within heartwood made it even heavier, harder, and more resistant to compression parallel to grain. A commercial use of this rare precious wood may contribute to juniper forests preservation in the frame of forest sustainable management plans. Key words: heartwood effect; Juniperus thurifera L.; physico-mechanical wood properties; wood classification; wood defects.

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Quantification of knots in dimension lumber using a single-pass X-ray radiation

Cited by 17 publications

References 5 publications

Improving strength grading of timber by grain angle measurement and mechanical modeling

Improving strength grading of timber by grain angle measurement and mechanical modeling

Automatic measurement of wood fiber orientation and knot detection using an optical system based on heating conduction

Physico-mechanical properties of Spanish juniper wood considering the effect of heartwood formation and the presence of defects and imperfections

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