scholarly journals DEFORMATION OF WOOD IN COMPRESSION DURING MOISTURE MOVEMENT

2017 ◽  
Vol 25 (2) ◽  
pp. 219-226
Author(s):  
S. Hamdan ◽  
M.S. Osman ◽  
M.Y. Chew
Keyword(s):  
Moisture Content ◽  
Elastic Limit ◽  
Wood Specimen ◽  
Compressive Load ◽  
Special Care ◽  
Moisture Movement ◽  
Viscoelastic Creep ◽  
Series Of Experiments

This work presents the phenomenon of mechano-sorptive strain in the deformation of wood during moisture content (MC) changes. A series of experiments were designed to demonstrate the greatly enhanced deformation due to the mechano-sorptive effect. The purpose of this work is to show the magnitude of mechano-sorptive creep compared to the ordinary viscoelastic creep with applied compressive load. In order to do this, several conditions were induced. They were the moisture movement with MC change, moisture movement without MC change and conditions without moisture movement. Several apparatus were assembled to produce the desired conditions. Special care is taken to make sure that the compressive load is relatively small and is within elastic limit. This work observed the unique patterns of strains of various conditions that were induced in the experiments. The characteristics shown in the results were evaluated logically and compared to existing theories to confirm their validity. The results have shown that with the presence of mechano-sorptive, the maximum strains of Jelutong (dyera costulata) wood specimens loaded at 200N is 0.433x10 -3 . The results showed that the severest deformation is caused by the increasing MC in the wood specimen, attributed to the mechanosorptive (MS) effect. 

scholarly journals Deformation of wood in compression during moisture movement

2017 ◽  
Vol 26 (2) ◽  
pp. 1-10
Author(s):  
Sinin Hamdan ◽  
Mahbub Hasan ◽  
Chew Meng Yew
Keyword(s):  
Moisture Content ◽  
Wood Specimen ◽  
Compressive Load ◽  
Moisture Movement ◽  
Viscoelastic Creep ◽  
Series Of Experiments

This work presents the phenomenon of mechano-sorptive strain in the deformation of wood during moisture content (MC) changes. A series of experiments were designed to demonstrate the greatly enhanced deformation due to the mechano- sorptive effect. The purpose of this work is to show the magnitude of mechano-sorptive creep compared to the ordinary viscoelastic creep with applied compressive load. In order to do this, the moisture movement with MC change, moisture movement without MC change and conditions without moisture movement were induced. The unique patterns of strains of various conditions induced in the experiments were observed. The characteristics shown in results were evaluated logically and compared to existing theories to confirm their validity. With the presence of mechano-sorptive, the maximumstrains of Jelutong (dyera costulata) wood specimens loaded at 200N is 0.433x10-3. The severest deformation is caused by the increasing MC in the wood specimen, attributed to the mechano-sorptive (MS) effect.

scholarly journals D EFORMATION OF WOOD IN C OMPRESSION DURING MOISTURE M OVEMENT

2017 ◽  
Vol 27 (2) ◽  
pp. 1-10
Author(s):  
Sinin Hamdan ◽  
Mahbub Hasan ◽  
Chew Meng Yew
Keyword(s):  
Moisture Content ◽  
Wood Specimen ◽  
Compressive Load ◽  
Moisture Movement ◽  
Viscoelastic Creep ◽  
Series Of Experiments

This work presents the phenomenon of mechano-sorptive strain in the deformation of wood during moisture content(MC)changes. A series of experiments were designed to demonstrate the greatly enhanced deformation due to the mechano-sorptive effect. The purpose of this work is to show the magnitude of mechano-sorptive creep compared to the ordinary viscoelastic creep with applied compressive load. In order to do this, the moisture movement with MC change, moisture movement without MC change and conditions without moisture movement were induced. The unique patterns of strains of various conditions induced in the experiments were observed. The characteristics shown in results were evaluated logically and compared to existing theories to confirm their validity. With the presence of mechano-sorptive, the maximum strains of Jelutong (dyera costulata)wood specimens loaded at 200N is 0.433x10-3. The severest deformation is caused by the increasing MC in the wood specimen, attributed to the mechano-sorptive(MS) effect. 

Modelling of the Development of the Vertical Density Profile of MDF during Hot Pressing

2007 ◽  
Vol 2 (2) ◽  
Author(s):  
Arun Gupta ◽  
Patrick Jordan ◽  
Shusheng Pang
Keyword(s):  
Moisture Content ◽  
Density Profile ◽  
Hot Pressing ◽  
Major Influence ◽  
Transfer Model ◽  
Uniform Density ◽  
Moisture Movement ◽  
Vertical Density Profile ◽  
Vertical Density ◽  
Pressing Operation

The hot pressing operation is one of the most important operations in medium density fibreboard (MDF) manufacture. Complicated dynamic interactions occur during pressing, including heat transfer, moisture movement, development of gas pressure, internal stress development and relaxation, wood consolidation, resin curing, bonding between particles and eventual development of a non-uniform density distribution through the panel thickness. Consequently the mat experiences continuously changing internal conditions (temperature and moisture content) as the pressing operation proceeds. The vertical density profile (VDP) has a major influence on the MDF strength and physical properties. This influence of the VDP on the board properties is generally recognised, but the formation of the density profile and their specific effects on the board performance have proved difficult to quantify. A mathematical model based on theoretical analysis and experimental information is being developed. In the model, the mat is divided into a number of thin parallel layers. The deformation of each layer is a function of stress, temperature and moisture content of the layer. The model incorporates the variation of the mat mechanical and rheological properties with moisture content and temperature. The changes in temperature and moisture content are provided by a separate heat and mass transfer model. The present model can predict stress, strain, layer deformation and density across the thickness during pressing. The performance of the model was validated by experiments conducted in a pilot-scale press. Twelve MDF boards were made with different pressing parameters, and the VDP were measured and compared with the simulation results from the model. The model could predict the density profile with an acceptable accuracy for the main variables that control the manufacturing of MDF boards.

The Influence of Wood Specimen Surface Coating on Moisture Movement during Drying

Holzforschung ◽  
2002 ◽  
Vol 56 (5) ◽  
pp. 541-546 ◽  
Author(s):  
R. Baronas ◽  
F. Ivanauskas
Keyword(s):  
Surface Coating ◽  
Transverse Section ◽  
Wood Specimen ◽  
Two Dimensional ◽  
Drying Process ◽  
Dimensional Model ◽  
Wood Drying ◽  
Moisture Movement ◽  
One Dimensional ◽  
The One

Summary A model of wood drying under isothermal conditions taking into consideration coating of the surface of a specimen is presented in this paper in a two-dimensional formulation. The influence of the surface coating degree as well as geometrical shape of a wood specimen on the dynamics of drying is investigated. Exponentials, describing the dependence of the halfdrying time on the degree of coating of the edges, as well as on the ratio of the width to the thickness of the transverse section of specimens from the northern red oak (Quercus rubra), are presented for drying from above the fiber saturation point. This paper describes the conditions of usage of the two-dimensional moisture transfer model in contrast to the one-dimensional model for accurate prediction of the drying process taking into consideration the coating of edges of specimens having a rectangular transverse section. A measure of reliability of the one-dimensional model to predict the wood drying process of sawn boards is introduced in this paper.

Orthotropic mechano-sorptive creep behavior of Chinese fir during the moisture adsorption process determined in tensile mode via dynamic mechanical analysis (DMA)

Holzforschung ◽  
2019 ◽  
Vol 73 (3) ◽  
pp. 229-239 ◽  
Author(s):  
Hui Peng ◽  
Jiali Jiang ◽  
Jianxiong Lu ◽  
Jinzhen Cao
Keyword(s):  
Moisture Content ◽  
Elastic Strain ◽  
Adsorption Process ◽  
Wood Cell Wall ◽  
Mechanical Analysis ◽  
Chinese Fir ◽  
Time Dependent ◽  
Unstable State ◽  
Viscoelastic Creep ◽  
Constant Moisture Content

AbstractThe orthotropic viscoelastic creep (VEC) at a constant moisture content (MC) and mechano-sorptive creep (MSC) during the adsorption process were examined for Chinese fir (Cunninghamia lanceolata) under tension at 20, 40, 60 and 80% relative humidity (RH) (30°C). Free swelling was performed on matched specimens based on the strain partition assumption to better understand the characteristics of the mechano-sorptive (MS) phenomenon. Expansion, elastic and time-dependent creep behaviors of radial (R) and tangential (T) specimens were affected by the MC to a higher degree than those of the longitudinal (L) specimen. A higher proportion of elastic strain in total strain was found in the L specimen as compared with transverse specimens, regardless of VEC and MSC. The RH level had a greater effect on relaxation behavior in the L specimen for MSC. According to the three tests, expansion mainly dominated the creep strain during adsorption, especially for the L specimen. The MS strain exerted more influence on transverse specimens and had less contribution to the L specimen. Moreover, under all RH isohume (RHI) conditions, the unstable state contributed to MS strain diminishing as MC approached equilibrium moisture content (EMC). A shorter adsorption time to a new equilibrium state was achieved at the expense of intensifying the unstable state of the wood cell wall.

HYSTERESIS EFFECTS IN SOIL MOISTURE MOVEMENT

1962 ◽  
Vol 42 (2) ◽  
pp. 247-253 ◽  
Author(s):  
W. J. Staple
Keyword(s):  
Moisture Content ◽  
Past History ◽  
Rate Of Change ◽  
Moisture Loss ◽  
Time Intervals ◽  
Moisture Movement ◽  
Wetting And Drying ◽  
The Past ◽  
History Of ◽  
Different Depths

Hysteresis was assessed by measuring the tension and moisture content of sections of soil at different time intervals during the redistribution of moisture in uniformly packed columns of Grenville silt loam. Moisture tension was measured by a null method and moisture content was measured gravimetrically.The rate of change of tension with moisture content dψ/dθ and hence the diffusivity, in the tension range 25 to 400 centimeters of water was more than twice as great for drying as for wetting. During redistribution of moisture, when both drying and wetting were involved, different ψ, vs. θ relationships existed at different depths, and the slopes dψ/dθ and diffusivities in the profile were often lower than those for either drying or wetting alone.Further work is needed to assess the importance of hysteresis on moisture movement in practical problems. It seems possible that data on hysteresis, and a knowledge of the past history of wetting and drying, may provide estimates of moisture loss and conservation in fallowed fields.

Measurement and Characterization of the Moisture-Induced Properties of ACF Package

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Ji-Young Yoon ◽  
Ilho Kim ◽  
Soon-Bok Lee
Keyword(s):  
Diffusion Coefficient ◽  
Relative Humidity ◽  
Moisture Content ◽  
Chemical Interaction ◽  
Transient State ◽  
Length Change ◽  
Experimental Results ◽  
Moisture Movement ◽  
Humid Environment ◽  
Swelling Coefficient

This study is to observe the exact behavior of anisotropic conductive adhesion (ACF) package under humid environments by obtaining the moisture-induced properties such as diffusion coefficient (the rate of moisture movement into the materials), saturated moisture content (the maximum absorbed quantity), and swelling coefficient (length change due to the chemical interaction). So the experiments were performed to get the moisture-induced properties of ACF and FR4 using newly developed method at various temperature and relative humidity conditions. Experimental results showed that the diffusion coefficient of ACF and FR4 follows Arrhenius’ equation very well, and the saturated moisture content of them follows Henry’s law, which means linear relationship between saturated moisture content and relative humidity, but the saturated moisture content of ACF is influenced by temperature as well as relative humidity. And the swelling coefficient of ACF and FR4 increases with temperature. Especially in the case of ACF, it shows the dramatic degradation due to Tg (glass transition temperature) at nearby 85°C. Finally, as using these experimental results, the behavior of the ACF package under humid environment is predicted through finite element simulation. When wetness defined by moisture content over saturated moisture content changes from 0 to 0.9, the center of the ACF package is subject to compression and the edge of the ACF package is subject to tension in the case of transient state. After all, because the edge of the ACF package is very weak due to bending moment, the failure is easy to occur under humid environment.

Experimental Study on Heat and Mass Transfer of Millet in a Fixed Furnace

2017 ◽  
Vol 13 (1) ◽  
Author(s):  
Conghui Gu ◽  
Zhulin Yuan ◽  
Yaming Yan ◽  
Dengshan Luo ◽  
Bin Li ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Moisture Content ◽  
Flow Velocity ◽  
Heat And Mass Transfer ◽  
Wall Temperature ◽  
Air Flow ◽  
Significant Drop ◽  
Drying Characteristics ◽  
Series Of Experiments ◽  
Air Flow Velocity

Abstract A series of experiments on the heat and mass transfer of millet particles are conducted in order to demonstrate the effects on drying characteristics of particles in this work. Experimental results illustrate that thermal conductivity between particles is significantly influenced by temperature and moisture content of millet particles. The temperature of particles in axial and radial direction increases because of the increase of inner wall temperature and decreases with the increase of air flow velocity. Moreover, the moisture content of particles near the inner wall has experienced a significant drop with the increase of inner wall temperature. As a consequence, the increase of air flow velocity results from the decrease of particles moisture content and drying rate of particles increases due to the increase of air flow velocity. Furthermore, the accumulated height of particles has barely influenced on the drying characteristics of millet particles.

scholarly journals The Influence of Specimen Size and Distance to a Surface on Resistive Moisture Content Measurements in Wood

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Maria Fredriksson ◽  
Johan Claesson ◽  
Lars Wadsö
Keyword(s):  
Boundary Condition ◽  
Moisture Content ◽  
Electrical Resistance ◽  
Wood Specimen ◽  
Electrical Potential ◽  
Electrical Current ◽  
Specimen Size ◽  
Equivalent Radius ◽  
Measured Moisture Content ◽  
Wood Surfaces

The moisture content of wood is commonly determined by measuring the electrical resistance between two electrodes inserted in the wood. However, problems using this method close to wood surfaces were reported in a previous study. In the present study, the effect of the distance to a surface and the specimen size on the measured electrical resistance was studied analytically as follows. The two electrodes create an electrical potential in the wood specimen. The boundary condition for the electrical potential is that the electrical current across all specimen surfaces is zero, which is achieved by using a suitable array of mirror sources. The analytical solution for the electrical potential was used to analyse the influence of the distance from the electrodes to the specimen surface as well as the size of the specimen. In addition, the error in moisture content was evaluated. The effect of the distance to a surface and the specimen size depended on the equivalent radius of the electrodes; if large electrodes are used in small specimens or close to surfaces, there is a risk that a higher resistance is measured which results in slightly lower measured moisture content than the actual moisture content of the specimen.

A Novel Comparison of Design-by-Analysis Methods

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Mark Stonehouse ◽  
Trevor G. Seipp ◽  
Shinichiro Kanamaru ◽  
Shawn Morrison
Keyword(s):  
Pressure Vessel ◽  
Elastic Limit ◽  
Compressive Load ◽  
Limit Load ◽  
Pressure Vessels ◽  
Elastic Plastic ◽  
Axial Compressive Load ◽  
Analysis Methods

There exist some atypical loads on pressure vessels during transportation. This is particularly true when the pressure vessel weighs over 500 tonnes. In this example vessel, the transportation was via rail on a “Schnabel car,” in which the vessel is suspended horizontally between the top nozzle and the skirt, and a significant axial compressive load is applied. During the evaluation of the stresses in the top head, a particularly novel situation was encountered which brought about some interesting issues with regards to the three design-by-analysis methods: elastic, limit load, and elastic-plastic. This paper discusses the comparison between all three of these design-by-analysis methods, and provides recommendations for which is most appropriate for this type of evaluation. Additional recommendations and warnings are provided for the use of the elastic and limit load methods as well.

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