A 3D micromechanical study of deformation curves and cell wall stresses in wood under transverse loading

Fortino, Stefania; Hradil, Petr; Salminen, Lauri; Magistris, Federica De

doi:10.1007/s10853-014-8608-2

Cited by 27 publications

(20 citation statements)

References 22 publications

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“…Latewood showed flattening of the cell and lateral expansion of the cells up to 35 % strain and s-shape deformation of the cell wall above 35 % strain. Recently, the same experimental deformations were evidenced in microFEM simulations by Fortino et al (2015). Tabarsa and Chui (2000) studied the stress-strain behaviour of earlywood and latewood during radial compression.…”

Section: Earlywood and Latewood Properties And Compression Mechanismssupporting

confidence: 52%

High strain rate radial compression of Norway spruce earlywood and latewood

et al. 2015

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The mechanical properties of Norway spruce were studied and a compression model for mechanical pulping was developed. The split-Hopkinson pressure bar technique was combined with high-speed photography to analyse local radial compression. Data analysis focussed on the differences between mechanical properties of earlywood and latewood. Measurements were conducted at both room temperature and 135°C. The effect of prefatigue treatment was also studied. A simple material model was defined linearly in parts and fitted to the measurement data to quantify the differences. New results were found on the differences in inelastic behaviour of earlywood and latewood at large deformations. In addition, other results were in line with previously published results.

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Section: Earlywood and Latewood Properties And Compression Mechanismssupporting

confidence: 52%

High strain rate radial compression of Norway spruce earlywood and latewood

et al. 2015

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“…The results showed that the cells collapse and undergo different deformation patterns as a result of compressive load. In a recent study by Fortino et al (2015), a bundle of wood cells was modelled with square and hexagonal shapes to study cell wall stresses under transverse loading. The authors found out increasing values of cell angles cause decreasing stress levels at the same deformation.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic study of microstructural deformation and stress in steam-exploded softwood

2017

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Steam explosion pretreatment results in the formation of microcracks in the cell walls of wood. In the present study, steam explosion experiments were performed and structural changes in Norway spruce were identified using scanning electron microscopy. The cellular structure of the softwood spruce was simulated using the finite element method, and the effects of pressure generated during the steam explosion pretreatment on the deformation of the cells were investigated. The simulated model included earlywood, latewood, and ray cells. The effects of bordered and cross-field pits on the stresses in the cell wall were studied as well. Many similarities were observed between the microcracks in the steam-exploded wood and the high-stress regions predicted by the model. The experimental and simulation results showed that the radial cell walls in the earlywood cells experienced major deformation. The presence of the pits created stress localization and facilitated the formation of microcracks in the cell walls.

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“…Therefore, the main cause for the boundary effects along the edges of the test specimens are the inhomogeneous internal structure (cross section assembly) of the test specimens and the influences of the annual ring orientation. The influences of the cell structure, discussed in detail in Fortino et al (2015), are not directly investigated, they are implicitly considered in the determination of the orthotropic shrinkage and swelling coefficients depending on the assembling of the crosssection (layers longitudinal and transverse).…”

Section: Analysis Of Boundary Effectsmentioning

confidence: 99%

Determination of the moisture change behavior of cross-laminated timber using an optical flow based computer vision technique

Hofinger

Pock

Moosbrugger³

2019

Wood Material Science & Engineering

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Although cross-laminated timber (CLT) offers greatly improved directional stability against moisture changes compared to lumber, some layup dependent directional differences still remain. Furthermore, even under a purely homogeneous distributed moisture change strong deformations appear along the boundaries, which show a decrease of swelling/shrinkage towards the inside of CLT panels. Metrological determination of this behavior is still a challenging task and involves longlasting moisture content conditioning and typically manual measurements. This limits the amount of measurable data-points and thus the gain-able insights. We apply a recently introduced computer vision technique based on optical flow from scan images to measure surface deformation fields of various CLT specimens with different layups. This allows us to measure the change of average differential swelling and shrinkage coefficients throughout the cross section and visualize them as curves with high resolution. We gain measurements for each image pixel and demonstrate good matching to previously published manual single-point measurements. Furthermore, we analyze various specimens specifically built to allow for investigations of the aforementioned boundary effects. Using the computer vision approach we are able to show how the combination of homogeneous deformations and boundary effects leads to the resulting deformations observable with manual methods.

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A 3D micromechanical study of deformation curves and cell wall stresses in wood under transverse loading

Cited by 27 publications

References 22 publications

High strain rate radial compression of Norway spruce earlywood and latewood

High strain rate radial compression of Norway spruce earlywood and latewood

Mechanistic study of microstructural deformation and stress in steam-exploded softwood

Determination of the moisture change behavior of cross-laminated timber using an optical flow based computer vision technique

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