SENSITIVITY OF SEVERAL SELECTED MECHANICAL PROPERTIES OF MOSO BAMBOO TO MOISTURE CONTENT CHANGE UNDER THE FIBRE SATURATION POINT

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%).

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Study on the Regularity of Soil Moisture Content Change after the Transformation of Sloping Farmland to Terrace in Southern Ningxia

Hans Journal of Agricultural Sciences ◽

10.12677/hjas.2021.117092 ◽

2021 ◽

Vol 11 (07) ◽

pp. 690-698

Author(s):

自慧岳

Keyword(s):

Soil Moisture ◽

Moisture Content ◽

Soil Moisture Content ◽

Content Change ◽

Southern Ningxia ◽

Sloping Farmland ◽

Moisture Content Change

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Deflection of Plywood Beams Due to Moisture Content Change

Transactions of the American Society of Civil Engineers ◽

10.1061/taceat.0006445 ◽

1950 ◽

Vol 115 (1) ◽

pp. 959-969

Author(s):

W. E. Wilson ◽

Laurence G. Olson

Keyword(s):

Moisture Content ◽

Content Change ◽

Moisture Content Change

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Testing of the fatigue strength along wood fibres at different moisture contents

Annals of WULS, Forestry and Wood Technology ◽

10.5604/01.3001.0015.5133 ◽

2021 ◽

Vol 115 ◽

pp. 45-54

Author(s):

Ewa Dobrowolska ◽

Mateusz Niedbała ◽

Daniel Tabaczyński

Keyword(s):

Fatigue Strength ◽

Moisture Content ◽

Maximum Stress ◽

Fibre Saturation Point ◽

Pedunculate Oak ◽

Saturation Point ◽

Moisture Contents ◽

Wood Fibres ◽

Short Term Strength ◽

Limited Usefulness

Testing of the fatigue strength along wood fibres at different moisture contents. The paper determines the effect of wood moisture content on the fatigue strength in compression along fibres. The method of determining the maximum stress at the proportional limit was used for the measurements. Fatigue strength was investigated for three wood species: pedunculate oak (Quercus robur L.), bearded birch (Betula pendula Roth.) and Norway spruce (Picea abies L.), with two moisture contents: close to the absolutely dry state and above the fibre saturation point. The ratio of fatigue strength to short term strength depends on moisture content and is similar for birch (70.3% in the dry state and 72.1% in the wet state), for oak (67.4% and 69.5% in both states) and for spruce (66.6% in the dry state and 68.1% in the wet state). The moisture content of the wood clearly influences the fatigue strength of the wood. On average, the fatigue strength of wood with moisture contents above the fibre saturation point constitutes about 0.20 of the fatigue strength of wood with moisture contents close to 0%. This tendency was found regardless of the tested species. The simplified method for testing fatigue strength at the limit of proportionality has shown its limited usefulness, requiring further analysis and comparison with other methods in order to be thoroughly tested and possibly improved.

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Research on the Process of Concrete Damage under Frost Action

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.163-167.3406 ◽

2010 ◽

Vol 163-167 ◽

pp. 3406-3410

Author(s):

Kai Zhi Ma ◽

Jian Guo Hou ◽

Ji Yao Jia

Keyword(s):

Moisture Content ◽

Test Range ◽

Freeze Thaw ◽

Frost Action ◽

Content Change ◽

Concrete Damage ◽

Moisture Content Change

This paper summarizes the theories of the concrete damage under frost action. Based on experiments done by researchers in and abroad, the water conversion and the moisture content change in the concrete during the freeze-thaw cycles are analyzed. In this paper, the affection of the expansion and contraction of ice on concrete at temperatures in the usual freeze-thaw test range is particularly taken into consideration. At last, a qualitative process of the concrete damage under frost action is proposed.

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Modelling drying processes of fuelbeds of Scots pine needles with initial moisture content above the fibre saturation point by two-phase models

International Journal of Wildland Fire ◽

10.1071/wf10119 ◽

2012 ◽

Vol 21 (4) ◽

pp. 418 ◽

Cited By ~ 4

Author(s):

Sen Jin ◽

Pengyu Chen

Keyword(s):

Moisture Content ◽

Scots Pine ◽

Initial Moisture Content ◽

Fibre Saturation Point ◽

Phase Model ◽

Fuel Moisture ◽

Drying Process ◽

Rating Systems ◽

Saturation Point ◽

Two Phase

Modelling the drying process of fuel moisture with initial moisture content above the fibre saturation point can be used to determine when fuel will become sufficiently dry (after precipitation) to burn and provide a more accurate prediction of fire potential. Based on analysis of the mechanism by which the drying process occurs, we propose a model comprising two phases distinguished by a moisture threshold of 0.35 g g–1, the fibre saturation point; one phase is controlled by evaporation and the other by diffusion. Each phase has a distinct equation with a different timelag. We compared our two-phase model with a one-phase model (one-timelag model) and another two-phase model by estimating drying of 15 Scots pine (Pinus sylvestris var. mongolica) needle fuelbeds. The results indicate that the two-timelag model improves moisture modelling, thereby reducing mean absolute error by more than 30%, i.e. from 0.0047 g g–1 (one-phase model) to 0.0030 g g–1. The model yields consistent results, further suggesting its potential for improving fuel moisture prediction of fire danger rating systems. The first timelag of the model is affected by fuelbed properties. Equations based on variables that represent fuelbed properties were established, thus saving time when estimating parameters for stand-specific fuel moisture models.

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Experimental study of electrode effects of resistance type electrodes for monitoring wood drying process above fibre saturation point / Elektroodefektide uurimine puidu kuivatamisel niiskussisaldustel üle kiu küllastuspunkti

Forestry Studies / Metsanduslikud Uurimused ◽

10.2478/v10132-012-0004-6 ◽

2012 ◽

Vol 56 (1) ◽

pp. 42-55

Author(s):

Valdek Tamme ◽

Peeter Muiste ◽

Regino Kask ◽

Allar Padari ◽

Hannes Tamme

Keyword(s):

Moisture Content ◽

Electrical Resistance ◽

Multivariate Calibration ◽

Fibre Saturation Point ◽

Saturation Point ◽

Residual Polarization ◽

Polarization Voltage ◽

Measurement Mode ◽

Repeated Use ◽

Effect Duration

Abstract Due to practical need to improve the accuracy of measurement of wood electrical resistance via creating multivariate calibration models the study of electrode effects was carried out. The experiments were made in DC mode and five types of electrode effects were measured: electrical resistance of the galvanic contact between the measuring electrode and wood, corrosion of measuring electrodes in wet wood, polarization and depolarization of the double layer forming on the surface of the measuring electrodes, residual polarization voltage between measuring electrodes and effect of repeated use of measuring electrodes. For multi-channel measurement mode effect of neighbouring electrodes was measured. Behind each of these factors is a complex transfer mechanism of free and bounded charge carriers from wood to measuring electrodes. Among the factors, polarization and depolarization have an immediate effect (duration of the processes in seconds) while resistance of electrode/wood contact, corrosion of electrodes and residual polarization have a slow effect (duration of processes in hours). For pine sapwood, coefficients of the Stamm formula were found in moisture contents (MC) above the fibre saturation point. It was determined that wood polarization and depolarization indicators are dependent on wood moisture content as is the case with wood electrical resistance. Compared to wood electrical resistance, wood polarization proved approximately four times and depolarization approximately eight times less sensitive to moisture content variation.

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