Full-field tracking and analysis of shrinkage strain during moisture content loss in wood

Holzforschung ◽  
2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Zongying Fu ◽  
Xiang Weng ◽  
Yufa Gao ◽  
Yongdong Zhou
Keyword(s):  
Moisture Content ◽  
Growth Ring ◽  
Shrinkage Strain ◽  
Tangential Direction ◽  
Saturation Point ◽  
Full Field ◽  
Parabolic Distribution ◽  
Ratio Curve ◽  
Radial Shrinkage ◽  
A Minor

AbstractAnisotropic shrinkage is a typically feature in wood, which is of critical importance in wood drying. In this study, the shrinkage strains over each growth ring were determined by a full-field strain measurement system during moisture content (MC) loss. Color maps were used to visualize the full-field distribution of displacement and shrinkage strain under different MC conditions. The variation of tangential and radial shrinkage strain from pith to bark, as well as the anisotropic shrinkage in heartwood and sapwood were studied. Both of the displacement and strain values increased as the MC decreased. From pith to bark, the tangential strains were higher at two poles as compared to the center, showing a parabolic distribution below fiber saturation point. While for radial shrinkage strain, a minor difference was observed except for the MC of 10%. An intersection between tangential and radial shrinkage ratio curve was observed at the MC of 28%. Both expansion and shrinkage in tangential direction were larger than radial counterparts, and the transformation from expansion to shrinkage occurred at the MC region of 32–28%. In addition, the shrinkage in heartwood was larger than sapwood, whereas anisotropic shrinkage in sapwood was more pronounced as compared to heartwood.

Physical properties of earlywood and latewood of Pinus radiata D. Don: Anisotropic shrinkage, equilibrium moisture content and fibre saturation point

Holzforschung ◽  
2005 ◽  
Vol 59 (6) ◽  
pp. 654-661 ◽  
Author(s):  
Shusheng Pang ◽  
Alfred Herritsch
Keyword(s):  
Moisture Content ◽  
Equilibrium Moisture Content ◽  
Pinus Radiata ◽  
Growth Ring ◽  
Fibre Saturation Point ◽  
Longitudinal Shrinkage ◽  
Saturation Point ◽  
Breast Height ◽  
Second Growth ◽  
Tangential Shrinkage

Abstract Anisotropic shrinkage (tangential and longitudinal), equilibrium moisture content (EMC) and fibre saturation point (FSP) were measured for separated earlywood (EW) and latewood (LW) of a 0.75-m-long log of 20-year old Pinus radiata that was cut at breast height from a selected tree in the forest of Central North Island, New Zealand. The experimental results have shown that at 12% moisture content (MC), tangential shrinkage was 3.23% for EW and 3.90% for LW, with an overall average of 3.56%. Longitudinal shrinkage was 0.23% for EW and 0.21% for LW with an overall average of 0.22%. Shrinkage for the oven dry (OD) state showed similar trends to those at 12% MC in terms of the differences between EW and LW. The tangential and longitudinal shrinkage varied significantly along the radius from pith to bark. The EW tangential shrinkage increased from pith to the seventh growth ring and then remained relatively constant until the last ring adjacent to the bark. The LW tangential shrinkage also increased from the pith outwards until the seventh growth ring, but beyond that was more variable than the EW shrinkage. Both EW and LW showed similar longitudinal shrinkage, with the highest values in the second growth ring, from which the shrinkage decreased exponentially towards the bark. LW had a slightly higher EMC than EW at a relative humidity (RH) below 80%, but the trend was reversed for RH above 80%. The EMC differences between EW and LW were less than 0.6%. The overall average FSP for Pinus radiata was 29.1%, with actual values varying from 25% to 32.8%. The earlywood FSP (28.9%) was slightly lower than that of the latewood (29.4%).

scholarly journals Moisture-Dependent Strength Properties of Thermally-Modified Fraxinus excelsior Wood in Compression

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1647 ◽  
Author(s):  
Edward Roszyk ◽  
Elżbieta Stachowska ◽  
Jerzy Majka ◽  
Przemysław Mania ◽  
Magdalena Broda
Keyword(s):  
Moisture Content ◽  
Strength Properties ◽  
Treatment Temperature ◽  
Thermal Modification ◽  
Fraxinus Excelsior ◽  
Mechanical Parameters ◽  
Saturation Point ◽  
Wood Moisture ◽  
Intrinsic Anisotropy ◽  
European Ash

European ash (Fraxinus excelsior L.) is one of the species commonly used for wood thermal modification that improves its performance. The presented research aimed to investigate a moisture-dependent strength anisotropy of thermally-modified European ash in compression. Wood samples were modified at 180 °C and 200 °C. Their mechanical parameters were determined in the principal anatomical directions under dry (moisture content of 3%) and wet (moisture content above fibre saturation point) conditions. Effect of heat treatment temperature and moisture content on the ash wood mechanical parameters concerning each anatomical direction were determined. The results show that thermal treatment kept the intrinsic anisotropy of wood mechanical properties. It decreased wood hygroscopicity, which resulted in improved strength and elasticity measured for wet wood when compared to untreated and treated samples. Higher treatment temperature (200 °C) increased wood elasticity in compression in all the anatomical directions despite wood moisture content during the measurements. Multivariate analysis revealed that the modification temperature significantly affected the modulus of elasticity perpendicular to the grain, while in the case of compression strength, the statistically significant effect was observed only parallel to the grain. The results obtained can be useful from an industrial perspective and can serve as part of a database for further modelling purposes.

scholarly journals Physical properties of sessile oak (quercus petraea l) used by the wood industry in Kosovo

2020 ◽  
Vol 2 (7) ◽  
pp. 278-285
Author(s):  
Rrahim Sejdiu ◽  
Florit Hoxha ◽  
Bujar Jashari ◽  
Lulzim Idrizi
Keyword(s):  
Specific Gravity ◽  
Moisture Content ◽  
Physical Properties ◽  
Radial Direction ◽  
Tangential Direction ◽  
Quercus Petraea ◽  
Sessile Oak ◽  
Content Ratio ◽  
Wet Condition ◽  
Shrinkage Coefficient

The paper shows some physical properties of sessile oak obtained in Kosovo regions. In the study are shown: wood shrinkage, specific gravity, shrinkage coefficient for 1% change of moisture content, ratio of shrinkage in tangential and radial direction etc. The amount of volumetric shrinkage of sessile oak is 15.95%, heartwood part has an average shrinkage 15.41% in The shrinkage of sapwood part is 17.56%. Specific gravity at: wet condition: (1.013gr/cm3); 12% (0.853gr/cm3) and 0% (0.826gr/cm3) of moisture content. Specific gravity of heartwood at: wet condition (1.05gr/cm3); 12% (0.88gr/cm3); 0% (0.85gr/cm3). The specific gravity of sapwood at: wet condition (0.91gr/cm3); 12% (0.77gr/cm3); 0% (0.748gr/cm3). The ratio of average shrinkage between tangential and radial cutting direction is 1.71%. This ratio was significantly higher in sapwood than heartwood. Coefficient of shrinkage (changing 1% of moisture content) in the radial direction is 0.00196, and 0.00323 in tangential direction.  

scholarly journals Effect of growth ring angle on lateral enlargement of compressed Cryptomeria japonica wood impregnated with polyethylene glycol

BioResources ◽  
2020 ◽  
Vol 15 (4) ◽  
pp. 8756-8769
Author(s):  
Chikara Mizoguchi ◽  
Hiroki Sakagami ◽  
Noboru Fujimoto ◽  
Tetsuya Nakao
Keyword(s):  
Polyethylene Glycol ◽  
Compression Ratio ◽  
Cryptomeria Japonica ◽  
Growth Ring ◽  
Local Area ◽  
Fiber Direction ◽  
Ratio Curve ◽  
Inflection Points ◽  
Weak Negative Correlation ◽  
Void Volumes

The lateral enlargement perpendicular to the compressive direction for small thin boards of Cryptomeria japonica was investigated to evaluate the effects of density and compressive directions to the radial (plane-sawn board) and 45 degrees of tilt to the radial (45º sawn board). Samples were impregnated with 200 and 20,000 molecular weight polyethylene glycol (PEG). The enlargement perpendicular to the fiber direction with deformation was obtained for heartwood and sapwood specimens treated only with PEG20,000. The compression ratio of specimens treated with PEG 20,000 exceeded the void volumes regardless of the wood density. Enlarged specimens of both sapwood and heartwood showed the inflection points in the force-compression ratio curve and no correlation between the compressive directions and lateral enlargement of specimens. In the local area showing the largest deformation, however, a weak positive correlation from plane-sawn boards and weak negative correlation from 45º sawn boards between the angles of compressive direction to growth ring and lateral enlargement were derived. Microfocus X-ray computer tomography in these areas showed the different morphological compressive deformations. The cells in the 45º sawn board were forced out due to each cell moving, whereas the radially arranged ones in the plane sawn board buckled under compression.

scholarly journals Moisture state variety in poplar lumber with moisture content above fibre saturation point during hot-press drying

2018 ◽  
Vol 64 (6) ◽  
pp. 730-737
Author(s):  
Junfeng Hou ◽  
Songlin Yi ◽  
Yongdong Zhou ◽  
Bin Pan
Keyword(s):  
Moisture Content ◽  
Fibre Saturation Point ◽  
Hot Press ◽  
Saturation Point ◽  
Moisture State

The relationship between moisture content and shrinkage strain in the process of bamboo air seasoning and cracking

2020 ◽  
pp. 1-10
Author(s):  
Yan Yan ◽  
BenHua Fei ◽  
ShengQuan Liu
Keyword(s):  
Moisture Content ◽  
Shrinkage Strain ◽  
The Relationship

Effect of blank pre-conditioning humidity on the dimensional accuracy and rigidity of paperboard trays

2018 ◽  
Vol 33 (2) ◽  
pp. 348-357
Author(s):  
Sami-Seppo Ovaska ◽  
Panu Tanninen ◽  
Esa Saukkonen ◽  
Kaj Backfolk
Keyword(s):  
Moisture Content ◽  
Dimensional Accuracy ◽  
Storage Conditions ◽  
Fiber Network ◽  
Bursting Strength ◽  
Press Forming ◽  
Layer Structures ◽  
A Minor ◽  
Moisture Conditions ◽  
Hygroscopic Behavior

Abstract Optimization of storage conditions is essential for successful converting of paperboard. This paper investigates the effect of blank moisture content on the dimensional accuracy and rigidity of press-formed paperboard trays. The trays were manufactured from uncoated, pigment-coated and extrusion-coated paperboards and multi-layer materials using fixed process parameters. Because of the different layer structures and coatings, the paperboards showed different hygroscopic behavior. Prior to converting trials, the bursting strength of paperboards under different moisture conditions was assessed. It was found that the moisture content has only a minor influence on bursting strength, but moisture affects blank curling tendency and dimensional accuracy of the tray. A high blank moisture content led to a loss of the dimensional stability and load-bearing capacity of trays, although based on earlier knowledge it is evident that the moisture content should be high for successful press-forming. As expected, a low blank moisture content increased the prevalence of ruptures in forming but the resulting trays were stiffer and their dimensional accuracy was better. It was suggested that the increased stiffness is related to a more efficient moisture removal during the press-forming, so that the fiber network is more effectively consolidated due to e. g. the formation of hydrogen bonds.

Experimental Investigation of Water Soaked Wood at Uniaxial and Biaxial States of Stress

1995 ◽  
Vol 48 (10) ◽  
pp. 684-688 ◽  
Author(s):  
M. Kowal ◽  
S. J. Kowalski
Keyword(s):  
Experimental Investigation ◽  
Stress State ◽  
Moisture Content ◽  
Radial Direction ◽  
Tangential Direction ◽  
Biaxial Stress ◽  
Growth Rings ◽  
Significant Difference ◽  
Free Swelling

It is possible to observe a significant difference in swelling strains of unstressed and stressed water soaked wood. This paper points out that the swelling strains depend not only on the magnitude of stress in wood but also on the kind of stress state. Our main aim is to investigate the relation between various states of stress and the swelling strains in water soaked wood. Three different states of stress are studied: tension in the radial direction, compression in the tangential direction with respect to the growth rings, and both these stresses acting together (biaxial stress). Some weighty conclusions follow from the investigations. The main one is that, although the mechanical strains alone are negligibly small compared to the free swelling strains, the coupled mechanical-swelling strains, being a function of the stress state and the moisture content, have a great significance in total strains of water soaked wood.

THE PENETRATION OF WATER VAPOR INTO WOOD

1930 ◽  
Vol 2 (5) ◽  
pp. 318-326 ◽  
Author(s):  
L. M. Pidgeon ◽  
O. Maass
Keyword(s):  
Water Vapor ◽  
Moisture Content ◽  
Pressure Gradient ◽  
Wood Structure ◽  
Saturation Point ◽  
Vapor Diffusion ◽  
Careful Control ◽  
Spring Balance ◽  
The Difference ◽  
Natural Drying

The rate of diffusion of water vapor through wood has been studied through a comparison of the time taken for samples of various thickness to become saturated. This process is, in a sense, the converse of natural drying, and for comparative purposes is more amenable to careful control of pressure and temperature. Continuous measurements of the amount of adsorption were carried out by the use of a quartz spring balance completely enclosed in the apparatus at a constant vapor pressure.Comparative numerical values have been obtained of the rate of diffusion of water vapor through spruce (Picea canadensis) and pine (Pinus banxiana) in various directions, through heartwood and sapwood, and through samples of different lengths. The results are considered as evidence that the movement of water through wood at concentrations below the saturation point, takes place as vapor diffusion through the spaces of the wood structure due to the pressure gradient consequent on the difference of moisture content.

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