Influence of Moisture Changes on Deformation of Wood Under Stress

Armstrong, L. D.; Christensen, G. N.

doi:10.1038/191869a0

Cited by 106 publications

(65 citation statements)

References 2 publications

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“…When the RH was reduced from 95% to 65% during the desorption cycle, FD had a continuously increased trend. This behavior agrees with those observed for wood under moisture cycling (Armstrong and Christensen 1961). The effect of borate treatment on FD for each strand board species group was clear.…”

Section: Moisture Content and Fractional Deflectionsupporting

confidence: 89%

“…The influence of moisture content (MC) change on wood creep properties has been recognized since the early 1960s (Armstrong and Christensen 1961;Ranta-Mannus 1975; Van der Put 1989;Wu and Milota 1995). There is a continued interest in providing experimental and theoretical understanding of the MS phenomena for wood and woodbased products (Montero et al 2012;Ozyhar et al 2013;Gril 2015;Jin et al 2016;Pérez-Pena et al 2016).…”

Section: Introductionmentioning

confidence: 99%

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Mechano-sorptive Deformation of Borate Modified Strand Board for Structural Uses

Li¹,

Sun

Lee

et al. 2017

BioResources

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Structural performance of chemically modified oriented strand board (OSB) has drawn great attention from builders, home insurance companies, and panel manufacturers. This study was conducted to provide time-dependent creep and moisture change-induced mechano-sorptive (MS) effect data from borate-treated and randomly formed strand board. The strand boards were lab-fabricated with flakes from southern yellow pine and mixed hardwoods. Commercial liquid phenol-formaldehyde resin was used as the binder. The treatments involved in the study were one level of zinc borate, one level of calcium borate, and two species groups that included separate controls. The load level, equivalent to 25% of the static bending modulus of rupture, was selected as a long-term constant load. Creep at 65% constant relative humidity (RH) developed in a normal time-dependent fashion and the Burger body creep model with four spring-dashpot elements was found appropriate to predict the creep response of borate modified strand board. Noticeable influence of borate modification on the fractional deflection was demonstrated under changing RH for both the absorption and desorption cycles. The measured fractional deflection due to the MS effect followed a linear relationship with moisture content change. The established material constants for various strand boards provided a way to predict the structural performance of treated strand board under varying RH conditions.

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Section: Moisture Content and Fractional Deflectionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Mechano-sorptive Deformation of Borate Modified Strand Board for Structural Uses

Li¹,

Sun

Lee

et al. 2017

BioResources

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“…Mechano-sorptive (MS) strain occurs when wood is subjected to stresses and changes in the moisture content (MC) (Armstrong and Kingston 1962). This strain is greater than the strain that occurs under constant MC conditions, is temperature-dependent, and is greater when the wood is under load (Mårtensson 1994).…”

Section: Introductionmentioning

confidence: 99%

“…The drying stresses cause permanent and transitory deformations on the wood, i.e., warping and internal checking. For E. nitens, Pérez et al (2013) observed that drying stresses in tension at the wood surface were higher at the early stage of wood drying, and the compression stresses at the wood surface increased to the maximum magnitude in late stages of drying of flatsawn boards.Mechano-sorptive (MS) strain occurs when wood is subjected to stresses and changes in the moisture content (MC) (Armstrong and Kingston 1962). This strain is greater than the strain that occurs under constant MC conditions, is temperature-dependent, and is greater when the wood is under load (Mårtensson 1994).…”

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confidence: 99%

Perpendicular Mechano-Sorptive Strains during Moisture Desorption from Eucalyptus nitens Specimens

et al. 2016

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aThe purpose of this paper was to determine the mechano-sorptive strains produced during desorption of moisture from Eucalyptus nitens specimens, from a perspective of modeling wood drying stresses. Eucalyptus nitens samples were tested in the radial and tangential directions. The mechano-sorptive strain was measured by cantilever bending during desorption. The runs were performed in a conditioning chamber at constant low temperature and variable equilibrium moisture content. Four load levels were considered for testing. The results showed that the mechano-sorptive strain during desorption of moisture was proportional to applied stress and reached the maximum value in the tangential direction. Also, the mechano-sorption coefficient depended on wood orientation and reached the maximum value of 5.46 × 10 -2 in the tangential direction. Bio-Bio, Av. Collao 1202, 4081112, Concepción, Chile; *Corresponding author: nattperez@gmail.com Keywords INTRODUCTIONChile has approximately 0.74 million hectares of Eucalyptus plantations available for industrial processing, and approximately 30% contain Eucalyptus nitens (INFOR 2015). E. nitens plantations are mainly distributed in the VIII and X regions, and they are the fastest growing species in Chile. E. nitens plantations grow as fast as 77 m 3 /ha/year (INFOR 1989), and they are well adapted to the cold winter conditions in Southern Chile (INFOR 2004).The volume of wood from E. nitens available in Chile for commercial use is estimated to reach 7 million m 3 per year in 2040 (INFOR 2015). This abundance is an incentive for processing this species into solid wood products for domestic and international markets. Unfortunately, the development of commercial solid products from this species is currently limited by the sawlog performance due to longitudinal growthstrains (Valencia et al. 2011) and drying difficulties due to their propensity of surface and internal checking, collapse, and higher transversal shrinkage (Ananías et al. 2009(Ananías et al. , 2014Sepúlveda et al. 2016). A more comprehensive understanding of the drying properties of E. nitens is essential for the successful processing of this species in commercial solid wood products.E. nitens is highly prone to internal checking (Leandro et al. 2008;Rebolledo et al. 2013). E. nitens of lower density tends to be associated with higher internal intra-ring PEER-REVIEWED ARTICLE bioresources.com Pérez et al. (2016). "Mechano-sorptive strain," BioResources 11(4), 8277-8284. 8278checking. The drying of E. nitens solid wood is also limited by collapse propensity (Ananías et al. 2009(Ananías et al. , 2014Sepúlveda et al. 2016). During the initial stages of drying, the surface layers shrink and exert compressive stresses on the core-wood, inducing drying stresses. These behaviors change with moisture content and temperature variations during drying. The drying stresses cause permanent and transitory deformations on the wood, i.e., warping and internal checking. For E. nitens, Pérez et al. (2013) observed that drying stres...

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“…Mechano-sorption (MS) strain is a phenomenon that occurs when wood is subjected to stresses and changes in the MC (Armstrong and Kingston 1962). This strain is considered to be greater than the strain that occurs under constant MC conditions (Mårtensson 1994).…”

Section: Introductionmentioning

confidence: 99%

Hygromechanical strains during the drying of Eucalyptus nitens boards

Pérez-Peña

Cloutier

Segovia

et al. 2016

Maderas, Cienc. tecnol.

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Collapse and drying stresses are currently induced during the drying of Eucalyptus nitens in solid wood products. The purpose of this study was to investigate these drying stresses by measuring hygromechanical strains during the drying of Eucalyptus nitens boards.Small samples of Eucalyptus nitens wood were oriented in the radial and tangential directions and tested to determine the hygromechanical strains during the drying process. This experimental work consisted of cantilevered bending tests conducted under variable relative humidity conditions. Tests were performed in a conditioning chamber at 30 °C with an equilibrium moisture content ranging from 22 to 12% under four levels of stress: 0, 10, 20 and 30% of the rupture load. The strains were determined using strain gauges, and the total deflection was measured with a linear variable differential transformer.The results show that in hygromechanical strains during the drying of Eucalyptus nitens, both the surface deformation and mechano-sorption strain were found to be proportional to the applied stress and reached their maximum values in the tangential direction. The total deflection increased 0,18 mm/mm with a surface deformation of 0,20 mm/mm, and the mechano-sorptive strain provides a greater contribution with a value of 0,11 mm/mm, thus corresponding to 59% of the total deformation. In attempts to improve the drying schedules of Eucalyptus nitens to develop solid wood products, mechano-sorptive behavior may be applied to relieve collapse and drying stress.

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Influence of Moisture Changes on Deformation of Wood Under Stress

Cited by 106 publications

References 2 publications

Mechano-sorptive Deformation of Borate Modified Strand Board for Structural Uses

Mechano-sorptive Deformation of Borate Modified Strand Board for Structural Uses

Perpendicular Mechano-Sorptive Strains during Moisture Desorption from Eucalyptus nitens Specimens

Hygromechanical strains during the drying of Eucalyptus nitens boards

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