Visual and machine strength grading of European ash and maple for glulam application

Kovryga, Andriy; Schlotzhauer, Philipp; Stapel, Peter; Militz, Holger; Kuilen, J.W.G. van de

doi:10.1515/hf-2018-0142

Cited by 13 publications

(29 citation statements)

References 19 publications

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“…Furthermore, the result of two adjusted grading schemes were compared-when the criterion "pith" is excluded from visual strength grading according to DIN 4074-5 [16] and when only single knots (DEB) are evaluated according to DIN 4074-5 [16]. Additionally, the lamellas were graded following the combined visual and machine grading proposed by Kovryga et al [31] and presented in Table 3. Figure 3 shows the grading results for ash and maple, respectively.…”

Section: Grading Resultsmentioning

confidence: 99%

“…The side products would raise the final yield. The final product-planed glulam lamellas-were subjected to destructive tensile testing after visual and machine strength grading (see sub sample "TH II" in Kovryga et al [31]).…”

Section: Sawn Green Lumber Planed Lamellas Maple Ashmentioning

confidence: 99%

“…The boundaries presented by Frese and Blaß [35] are fitted to beech lamellas. For the present study, the combined grading is optimized for ash and maple and presented by the paper Kovryga et al [31]. Table 3 shows the combination of boundary values selected for the current study.…”

Section: Combined Visual and Machine Strength Gradingmentioning

confidence: 99%

“…Table 3 shows the combination of boundary values selected for the current study. As example, for maple the "Solution B" and for ash the "Solution C" proposed for combined grading by Kovryga et al [31] is selected. The presented combination allows grading to three different grades plus reject group.…”

Section: Combined Visual and Machine Strength Gradingmentioning

confidence: 99%

“…Table 3. Optimized grading rules for combined visual and machine strength grading of ash and maple (according to Kovryga et al [31]; maple: "Solution B", ash: "Solution C").…”

Section: Combined Visual and Machine Strength Gradingmentioning

confidence: 99%

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Analysis of Economic Feasibility of Ash and Maple Lamella Production for Glued Laminated Timber

Schlotzhauer

Kovryga

Emmerich

et al. 2019

Forests

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Background and Objectives: In the near future, in Europe a raised availability of hardwoods is expected. One possible sales market is the building sector, where medium dense European hardwoods could be used as load bearing elements. For the hardwood species beech, oak, and sweet chestnut technical building approvals already allow the production of hardwood glulam. For the species maple and ash this is not possible yet. This paper aims to evaluate the economic feasibility of glulam production from low dimension ash and maple timber from thinnings. Therefore, round wood qualities and the resulting lumber qualities are assessed and final as well as intermediate yields are calculated. Materials and Methods: 81 maple logs and 79 ash logs cut from trees from thinning operations in mixed (beech) forest stands were visually graded, cant sawn, and turned into strength-graded glulam lamellas. The volume yield of each production step was calculated. Results: The highest volume yield losses occur during milling of round wood (around 50%) and “presorting and planning” the dried lumber (56–60%). Strength grading is another key process in the production process. When grading according to DIN 4074-5 (2008), another 40–50% volume loss is reported, while combined visual and machine grading only produces 7–15% rejects. Conclusions: Yield raise potentials were identified especially in the production steps milling, presorting and planning and strength grading.

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Section: Grading Resultsmentioning

confidence: 99%

Section: Sawn Green Lumber Planed Lamellas Maple Ashmentioning

confidence: 99%

Section: Combined Visual and Machine Strength Gradingmentioning

confidence: 99%

Section: Combined Visual and Machine Strength Gradingmentioning

confidence: 99%

“…Table 3. Optimized grading rules for combined visual and machine strength grading of ash and maple (according to Kovryga et al [31]; maple: "Solution B", ash: "Solution C").…”

Section: Combined Visual and Machine Strength Gradingmentioning

confidence: 99%

See 3 more Smart Citations

Analysis of Economic Feasibility of Ash and Maple Lamella Production for Glued Laminated Timber

Schlotzhauer

Kovryga

Emmerich

et al. 2019

Forests

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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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Strength and stiffness predictions with focus on different acoustic measurement methods

2020

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Strength grading is an important step for the production of homogenous and high-quality solid wood material. In particular, for hardwoods, the use of non-visible characteristics is indispensable. Dynamic MOE (Edyn) is an important parameter widely used for grading of softwoods and applicable to hardwoods as well. There are two common ways to measure Edyn—ultrasound (US) wave propagation and longitudinal vibration (LV) method. Both methods are used in practice, however, due to the different inherent measurement techniques, the results differ. The current paper analyses the stiffness and strength coefficients of determination for several temperate European hardwood species and emphasizes the differences between the two measurement systems. The performance was analysed with regard to grading techniques, testing modes for the mechanical properties (tension and bending) and wood qualities. For more than 2861 pieces of European ash (Fraxinus excelsior), European beech (Fagus sylvatica), European oak (Quercus spp.) and maple (Acer spp.), the Edyn was measured using both techniques, and destructive tests (tension and edgewise bending) were applied. The results show that LV has higher coefficient of determination compared to the US Edyn. The coefficient of determination for both methods and tensile application can be increased by calculating Edyn with average density. Furthermore, the results support species-independent strength grading of hardwoods. Further research on the effect of different wood qualities and sawing patterns is required.

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Visual and machine strength grading of European ash and maple for glulam application

Cited by 13 publications

References 19 publications

Analysis of Economic Feasibility of Ash and Maple Lamella Production for Glued Laminated Timber

Analysis of Economic Feasibility of Ash and Maple Lamella Production for Glued Laminated Timber

Strength grading of hardwoods using transversal ultrasound

Strength and stiffness predictions with focus on different acoustic measurement methods

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