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

Daval, Vincent; Pot, Guillaume; Belkacemi, M.; Mériaudeau, Fabrice; Collet, Robert

doi:10.1364/oe.23.033529

Cited by 29 publications

(16 citation statements)

References 16 publications

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“…[5] Measured the length of ellipse minor and major axes on Japanese beech (Fagus crenata Blume) and sugi (Cryptomeria japonica D.Don) on sawn and planed wood surfaces, while rotating samples. They showed that, for both species, the grain angle measurement error on the planed samples was lower than on rough-sawn samples (maximum error of 4.6° for rough-sawn sugi), which is in accordance with [9] on Douglas fir. In [5], no analysis was provided regarding the major and minor axis length for the two species and two surface machining, and only one laser dot was used [10].…”

Section: Introductionsupporting

confidence: 64%

Influence of wood anatomy on fiber orientation measurement obtained by laser scanning on five European species

et al. 2020

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In order to obtain high production rates of sawn timber, the sawmilling industry can use laser scanning, allowing knot detection and machine strength grading. In particular, laser scanners measure grain angle using the so-called tracheid effect on wood surface where an elliptic scattering of the laser light can be observed. This paper aims to describe the light scattering obtained by a laser beam projection on wood surface and to assess the accuracy of such fiber orientation measurement on five European species. Firstly, fiber orientation measurement error was assessed by rotating samples. Secondly, the description of the scattering effect was done considering ellipse axis ratios and areas. This was studied according to several parameters such as wood surface machining, moisture content, and orthotropic planes of symmetry. Fiber orientation measurement was successfully performed on all the tested species. The measurement error was below 1.6°, except for oak longitudinal–radial (LR) plane showing an error up to 3.1°. For most of the species, the error was higher in LR plane because of the influence of medullary rays. Despite the observation of major variabilities in laser light scattering, it was possible to measure the grain angles with a good accuracy for all investigated species.

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Section: Introductionsupporting

confidence: 64%

Influence of wood anatomy on fiber orientation measurement obtained by laser scanning on five European species

et al. 2020

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“…The resolution of the fibre orientation data obtained was 1 mm in the direction along the board and 4 mm in the transversal direction of the board. It is worth noting that because of the rough sawn surface of the Norway spruce and Douglas fir boards, the fibre orientation data was somewhat noisy, as described by Daval et al (2015). Figure 1 shows four wood surfaces (a-d) of a 150-mmlong part of one of the Norway spruce boards (the appearance would be similar for a board of Douglas fir) 50 × 100 mm in size, scanned by the industrial scanner.…”

Section: Determination Of Local Fibre Orientationmentioning

confidence: 99%

“…According to the research referred to above, the possibility of determining fibre orientation on board surfaces of softwood species using the tracheid effect is well documented. However, both Zhou and Shen (2003) and Daval et al (2015) found that this effect is more difficult to discern on hardwoods. As for oak, this was explained by the high density and short length of oak fibres, resulting in an insufficient diffusion of laser light and small size of the laser dot emerging on the board surface.…”

Section: Introductionmentioning

confidence: 98%

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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“…More recent results show the potential of such measurements for hardwoods, particularly for oak (Olsson et al 2018). Application of other NDT techniques to hardwoods, such as thermal conductivity measurement (Daval et al 2015) and automated visual analysis of the spindle patterns (Ehrhart et al 2018) has been on the research agenda.…”

Section: Introductionmentioning

confidence: 99%

Strength grading of hardwoods using transversal ultrasound

2020

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Detection of local wood inhomogeneities is important for accurate strength and stiffness prediction. In hardwood specimens, visual characteristics (e.g. knots or fibre deviation) are difficult to detect, either with a visual surface inspection or by the machine. Transversal ultrasound scan (TUS) is a non-destructive evaluation method with high potential for hardwoods. The method relies on differences in ultrasound wave propagation in perpendicular to the grain direction. The aim of this study is to estimate and analyse the capabilities of TUS for defect detection in hardwoods and prediction of mechanical property values. In the current paper, the TUS was applied to the hardwood species European ash (Fraxinus excelsior L.), Norway maple (Acer platanoides L.) and sycamore maple (Acer pseudoplatanus L.). In total, 16 boards of both specimens were completely scanned perpendicular to the grain using a laboratory scanner with dry-coupled transducers. The measurements were processed to 2D scan images of the boards, and image processing routines were applied to further feature extraction, defect detection and grading criteria calculation. In addition, as a reference for each board, all relevant visual characteristics and mechanical properties from the tensile test were measured. Using the TUS global fibre deviation, the size and the position of the knots can be detected. Knottiness correlates to the strength properties similarly or even better compared to the manual knottiness measurement. Between the global fibre angle measured using TUS and measured on the failure pattern, no correlation could be found. The ultrasound modulus of elasticity perpendicular to the grain does not show any meaningful correlation to the elastic properties parallel to the grain. In overall, TUS shows high potential for the strength grading of hardwoods.

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

Cited by 29 publications

References 16 publications

Influence of wood anatomy on fiber orientation measurement obtained by laser scanning on five European species

Influence of wood anatomy on fiber orientation measurement obtained by laser scanning on five European species

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 of hardwoods using transversal ultrasound

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