A numerical study of the shape stability of sawn timber subjected to moisture variation Part 2: Simulation of drying board

Ormarsson, Sigurdur; Dahlblom, Ola; Petersson, Hans

doi:10.1007/s002260050126

Cited by 46 publications

(28 citation statements)

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“…Decrease in torque and twist was achieved by increasing the drying temperature and pre-steaming of the material prior to drying. The same relationship between torque and MC was confirmed in drying simulations using the finite element method (Ormarsson et al 1999) and in static climatic conditioning (Bäckström and Kliger 2006). …”

Section: Introductionsupporting

confidence: 54%

The influence of material properties on the amount of twist of spruce wood during kiln drying

et al. 2010

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The development of twist in Norway spruce boards (Picea abies Karst.) during normal temperature kiln drying was researched. Tangentially oriented boards were sawn from diametrical radial planks, from which the basic wood properties, i.e. linear shrinkage and grain angle, were determined. The unrestrained boards were kiln dried using a selected drying schedule. During the controlled drying process the moisture content (MC) and twist of the boards were measured. Twist was generally induced by the shrinkage of wood below the fibre saturation point, and increased in proportional to the decrease in MC. The earlier appearance of twist, with regard to MC and drying time, was confirmed in the case of boards sawn from the central part of logs. The final twist amounted to between 10 and 20 °/m in the case of boards close to the pith, and decreased to less than 4 °/m in the case of boards sawn at a radius of 70 mm from the centre of the logs. Ring curvature had the highest impact on the final twist of the dried boards, followed by grain angle and tangential shrinkage. Einfluss der

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Section: Introductionsupporting

confidence: 54%

The influence of material properties on the amount of twist of spruce wood during kiln drying

et al. 2010

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“…FEM was performed by means of the FE software (Abaqus 2008) based on special routines for wood distortion developed earlier by Ormarsson et al (1998Ormarsson et al ( , 1999. The routines take into account that wood is a moisture sensitive (cylindrical) orthotropic material concerning stiffness, shrinkage, and mechanosorption behavior.…”

Section: Methodsmentioning

confidence: 99%

“…It should be observed whether the discs are cracked and how is the crack development in the course of the drying process. The experimental disc samples will also be simulated by a 3D distortion model developed by Ormarsson et al (1998Ormarsson et al ( , 1999. The crack simulation by finite element modeling (FEM) in the present study is based on description of a cohesive crack model for wood.…”

Section: Introductionmentioning

confidence: 99%

Experimental and finite element study of the effect of temperature and moisture on the tangential tensile strength and fracture behavior in timber logs

Larsen

Ormarsson

2013

Holzforschung

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Timber is normally dried by kiln drying, in the course of which moisture-induced stresses and fractures can occur. Cracks occur primarily in the radial direction due to tangential tensile strength (TSt) that exceeds the strength of the material. The present article reports on experiments and numerical simulations by finite element modeling (FEM) concerning the TSt and fracture behavior of Norway spruce under various climatic conditions. Thin log disc specimens were studied to simplify the description of the moisture flow in the samples. The specimens designed for TS were acclimatized to a moisture content (MC) of 18% before TSt tests at 20°C, 60°C, and 90°C were carried out. The maximum stress results of the disc simulations by FEM were compared with the experimental strength results at the same temperature levels. There is a rather good agreement between the results of modeling and experiments. The results also illustrate the strong decrease of TSt with increasing temperature at a constant MC level.

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“…Leavengood (2001) developed an Excel spreadsheet that estimates the dimensional change in wood with moisture loss (or gain) using a related approach, but does not provide an indication of cup magnitude. Ormarsson et al (1998Ormarsson et al ( , 1999Ormarsson et al ( , 2000 have developed a complex model that uses finite element simulations and considers mechano-sorptive and visco-elastic behaviors of drying wood that predict dimensional changes and warp, but this model is beyond the scope of the current, more pragmatic approach to estimating cup.…”

Section: Introductionmentioning

confidence: 99%

Modeling the Cupping of Lumber

Mitchell¹

2016

BioResources

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Wood shrinks anisotropically as it loses hygroscopic moisture. While longitudinal shrinkage (parallel to the grain) is nearly negligible in normal wood, transverse shrinkage (across the grain) is significant and characterized as tangential and radial shrinkage. The application of average tangential shrinkage values to a rectangular cross section results in errors, especially for boards cut from near the center of the log. In addition, using a Cartesian coordinate system to calculate shrinkage cannot provide an estimate of cup. Calculating shrinkage and cup deformation using a previously developed model, this Excel model can provide a more realistic image of the final cross section and a more accurate estimate of shrinkage. The model is dependent on wood species, initial and final moisture contents, and location of the board within the log. This paper describes and illustrates uses of the model.

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A numerical study of the shape stability of sawn timber subjected to moisture variation Part 2: Simulation of drying board

Cited by 46 publications

References 0 publications

The influence of material properties on the amount of twist of spruce wood during kiln drying

The influence of material properties on the amount of twist of spruce wood during kiln drying

Experimental and finite element study of the effect of temperature and moisture on the tangential tensile strength and fracture behavior in timber logs

Modeling the Cupping of Lumber

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