Discussion of common and new indicating properties for the strength grading of wooden boards

Lukacevic, Markus; Füssl, Josef; Eberhardsteiner, Josef

doi:10.1007/s00226-015-0712-1

Cited by 35 publications

(17 citation statements)

References 17 publications

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“…Such data is determined using the tracheid effect which is based on the fact that fibres in wood spread concentrated light, such as laser light, better in the longitudinal direction of the fibres than across (Matthews and Beech 1976). Since strength and stiffness properties are far better in the longitudinal fibre direction than in perpendicular directions (Kollman and Côté 1968;Hatayama 1984), even a small angle between fibre direction and longitudinal board direction implies a substantial decrease of local stiffness and strength of a board. Based on information about fibre orientation, axial dynamic MoE, basic material wood properties and cross-sectional integration schemes, a novel IP for bending strength of Norway spruce (Picea abies L.) was defined by Olsson et al (2013) as the lowest calculated local edgewise bending MoE found along the board.…”

Section: Introductionmentioning

confidence: 99%

“…An investigation carried out by Olsson and Oscarsson (2017) and comprising more than 900 boards of Norway spruce gave evidence of the performance of the method and this IP. Research aiming at utilization of fibre orientation data for machine strength grading has also been presented by Jehl (2012), Viguier et al (2015), Viguier et al (2017) andLukacevic et al (2015).…”

Section: Introductionmentioning

confidence: 99%

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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.)

Olsson

Pot

Viguier

et al. 2018

Annals of Forest Science

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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.)Abstract & Key message Machine 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 abies L.) and Douglas fir (Pseudotsuga menziesii (Mirb.) Franco). For European oak (Quercus petraea (Matt.) Liebl./Quercus robur L.) boards of narrow dimensions, axial vibratory measurements are ineffective whereas satisfactory results are achieved using a model based on fibre orientation. & Context Machine strength grading of sawn timber is an important value adding process for the sawmilling industry. & Aims The 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.). & Methods The 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. & Results Whereas 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.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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.)

Olsson

Pot

Viguier

et al. 2018

Annals of Forest Science

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“…Among these is a research group at TU Wien which, on the basis of X-ray and reconstruction of knots in 3D, recently has suggested new IPs for strength grading, for example, Lukacevic et al (2015). Another group, based in France and involving several universities and institutes, has suggested grading on the basis of X-ray in combination with fibre orientation information from tracheid effect scanning, for example Viguier et al (2015).…”

Section: Introductionmentioning

confidence: 99%

Strength grading on the basis of high resolution laser scanning and dynamic excitation: a full scale investigation of performance

Olsson

Oscarsson

2016

Eur. J. Wood Prod.

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Effective utilization of structural timber requires grading and indicating properties (IPs) that are able to predict strength with high accuracy and machines that are able to measure the underlying board properties at a speed that corresponds to the production speed of sawmills. The aim of this research is to assess the performance of a new machine strength grading method/procedure which was recently approved for the European market and to compare the performance of it with the performance of other available techniques. The novel method is based on laser scanning utilizing the tracheid effect, in combination with data from dynamic excitation and weighing. Applied indicating properties are defined in detail and results presented include assessment of the repeatability, coefficients of determination between IPs and grade determining properties, and examples of the yield achieved in different strength classes and combinations of strength classes. The investigated sample comprised more than 900 pieces of timber of Norway spruce (Picea abies) from Sweden, Norway and Finland. For this sample the coefficient of determination between the IP to bending strength and the measured bending strength was as high as R 2 = 0.69, while the coefficient of determination between dynamic modulus of elasticity (MOE) and measured bending strength was R 2 = 0.53. The yield in high strength classes, C35 and above, becomes about twice as high using the new method/ procedure compared to machines using dynamic MOE as IP. A comparison of the performance with what has been presented for machines that are based on X-ray in combination with dynamic excitation indicates that the new method/procedure will surpass such machines as well.

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“…c After the regrouping procedure has been applied, only the most important knot groups are retained in the model. The resulting stiffness profiles using the approach outlined in (Kandler et al 2015) as well as the 3D FE approach (Lukacevic and Füssl 2014) for each knot group are displayed in d. In e, different strength profiles according to IPs 1 to 4 are displayed presented in Lukacevic et al (2015), different combinations of the following parameters were considered: -Knot-area-ratio (KAR), which is the ratio between the knot area of all knots of a knot group projected on the cross section and the cross section area. -Knot area, which denotes the knot area visible on the surface of the board.…”

Section: Strength Profilesmentioning

confidence: 99%

Experimental study on glued laminated timber beams with well-known knot morphology

2018

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Nowadays, the impact of knots on the failure behaviour of glued laminated timber (GLT) beams is considered by subjecting the single lamellas to a strength grading process, where, i.a., tracheid effect-based laser scanning is used to obtain information about knot properties. This approach single-handedly defines the beam's final strength properties according to current standards. At the same time, advanced production processes of such beams would allow an easy tracking of a scanned board's location, but, at this point, previously obtained detailed information is already disregarded. Therefore, the scanning data is used to virtually reconstruct knot geometries and group them into sections within GLT beams. For this study, a sample of 50 GLT beams of five different configuration types was produced and tested under static four-point-bending until failure. As for each assembled lamella the orientation and position within the corresponding GLT beam is known, several parameters derived from the reconstructed knots can be correlated to effective GLT properties. Furthermore, the crack patterns of the tested beams are manually recorded and used to obtain measures of cracks. A detailed analysis of the generated data and their statistical evaluation show that, in the future, dedicated mechanical models for such timber elements must be developed to realistically predict their strength properties. A potential approach, using fluctuating section-wise effective material properties, is proposed.

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Discussion of common and new indicating properties for the strength grading of wooden boards

Cited by 35 publications

References 17 publications

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.)

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.)

Strength grading on the basis of high resolution laser scanning and dynamic excitation: a full scale investigation of performance

Experimental study on glued laminated timber beams with well-known knot morphology

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