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Performance of strength grading methods based on fibre orientation and axial resonance frequency applied to Norway spruce (Picea abies L.), Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) and European oak (Quercus petraea (Matt.) Liebl./Quercus robur L.)
Linnaeus University, Faculty of Technology, Department of Building Technology.ORCID iD: 0000-0002-6410-1017
LaBoMaP, France.
LaBoMaP, France.
LaBoMaP, France.
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2018 (English)In: Annals of Forest Science, ISSN 1286-4560, E-ISSN 1297-966X, Vol. 75, no 4, article id 102Article in journal (Refereed) Published
Abstract [en]

Key messageMachine strength grading of sawn timber is an important value adding process for the sawmilling industry. By utilizing data of local fibre orientation on timber surfaces, obtained from laser scanning, more accurate prediction of bending strength can be obtained compared to if only axial vibratory measurements are performed. However, the degree of improvement depends on wood species and on board dimensions. It is shown that a model based on a combination of fibre orientation scanning and axial vibratory measurement is very effective for Norway spruce (Picea abiesL.) and Douglas fir (Pseudotsuga menziesii(Mirb.) Franco). For European oak (Quercus petraea(Matt.) Liebl./Quercus roburL.) boards of narrow dimensions, axial vibratory measurements are ineffective whereas satisfactory results are achieved using a model based on fibre orientation.ContextMachine strength grading of sawn timber is an important value adding process for the sawmilling industry.AimsThe purpose of this paper has been to compare the accuracy of several indicating properties (IPs) to bending strength when applied to Norway spruce (Picea abies L.), Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) and European oak (Quercus petraea (Matt.) Liebl./Quercus robur L.).MethodsThe IPs were determined for a set of data comprising scanned high-resolution information of fibre orientation on board surfaces, axial resonance frequency, mass and board dimensions.ResultsWhereas dynamic axial modulus of elasticity (MoE) gave good prediction of bending strength of Norway spruce (R-2=0.58) and Douglas fir (R-2=0.47), it did not for narrow dimension boards of oak (R-2=0.22). An IP based on fibre orientation gave, however, good prediction of bending strength for all three species and an IP considering both dynamic axial MoE and local fibre orientation for prediction of bending strength gave very good accuracy for all species (Norway spruce R-2=0.72, Douglas fir R-2=0.62, oak R-2=0.59). Comparisons of results also showed that scanning of fibre orientation on all four sides of boards resulted in more accurate grading compared to when only the two wide faces were scanned.ConclusionData of local fibre orientation on wood surfaces give basis for accurate machine strength grading. For structural size timber of Norway spruce and Douglas fir, excellent grading accuracy was achieved combining such data with data from vibratory measurements. The improvements achieved enable substantial increase of yield in high-strength classes.

Place, publisher, year, edition, pages
Springer, 2018. Vol. 75, no 4, article id 102
Keywords [en]
Grain angle, Fibre direction, Tracheid effect, Structural timber, Longitudinal vibrations, Grade determining property
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
URN: urn:nbn:se:lnu:diva-79603DOI: 10.1007/s13595-018-0781-zISI: 000451958200001Scopus ID: 2-s2.0-85057618631OAI: oai:DiVA.org:lnu-79603DiVA, id: diva2:1280461
Available from: 2019-01-18 Created: 2019-01-18 Last updated: 2019-10-17Bibliographically approved

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Olsson, AndersOscarsson, Jan

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