[논문]Effects of Density, Temperature, Size, Grain Angle of Wood Materials on Nondestructive Moisture Meters

Pang, Sung-Jun; Jeong, Gi Young

doi:10.5658/wood.2019.47.1.40

Effects of Density, Temperature, Size, Grain Angle of Wood Materials on Nondestructive Moisture Meters 원문보기

목재공학 = Journal of the Korean wood science and technology, v.47 no.1, 2019년, pp.40 - 50

Pang, Sung-Jun (Department of Wood Science and Engineering, Chonnam National University) , Jeong, Gi Young (Department of Wood Science and Engineering, Chonnam National University)

Abstract ▼ AI-Helper

The aim of this study was to investigate the effects of density, temperature, size, and grain direction on measurement of moisture contents (MC) of wood materials non-destructively. The MC of different sizes of solid wood, glulam, and CLT from larch (larix kaempferi, $560kg/m^3$) and pine (pinus koraiensis, $430kg/m^3$) were measured using the dielectric type and resistance type meters. The specimens were conditioned in the environmental chamber to be equilibrium moisture content (EMC) of 12 % and 19 %. When density setting in dielectric type meter was increased from $400kg/m^3$ to $600kg/m^3$, the MCs of specimen (S-L-100-E) were decreased from 13.4 % to 11.3 %. However, when wood group (WG) setting in resistance type meter was changed from WG1 to WG4, the measured MCs were increased from 9.2 % to 12.3 %. When temperature setting in resistance type meters was changed from 0 to $35^{\circ}C$, the MC was decreased from 17.0 % to 13.0 %. The MCs measured by dielectric type meter for larger specimens (S-L-100-E_11.3 %, G-L-240-E_11.7 % and C-L-120-E_12.8 %) were higher than those of small size specimens (S-L-30-E_8.7 %, G-L-150-E_10.3 %, and C-L-90-E_9.7 %). The MCs measured by resistance type meter for larger specimens (G-L-240-E_11.6 % and C-L-120-E_13.3 %) were also higher than those of small size specimens (G-L-150-E_10.4 %, and C-L-90-E_11.8 %). The resistance type meter was not affected by the grain direction but the dielectric type meter were affected by the grain direction. The MC measured by resistance type meter for G-L-120-E perpendicular to grain direction was 11.5 % and the measured MC parallel to grain direction was 11.3 %. The MC measured by dielectric type meter parallel to grain direction (12.1 %) was higher than that measured perpendicular to grain direction (10.7 %).

주제어

표/그림 (11)

그림 Fig. 1. Types and orientations of specimens.
표 Table 1. Nomenclatures of specimens depending on the specimen conditions
그림 Fig. 2. Procedures for conditioning and measuring of moisture contents of specimens.
그림 Fig. 3. Schematic diagram to measure the moisture contents of specimens by using portable moisture meters.
그림 Fig. 4. Combinations of specimens for evaluating the detectable depth of meters.
그림 Fig. 5. Moisture contents depending on the contacted grain direction and species, as well as the wood group options in MC-380XCA (Condition of environmental chamber: EMC 12 % Temperature of testing room:20 ℃).
그림 Fig. 6. Moisture contents depending on the contacted surface and grain direction of specimen, as well as the wood group options in MC-460 (G-L-120-E specimen, Condition of environmental chamber: EMC 12 %, Condition of temperature setting of the meter: 20 ℃, Temperature of testing room: 20 ℃).
그림 Fig. 7. Moisture contents of wood materials depending on the temperature option in MC-460 (Condition of environmental chamber: EMC 12 %, Condition of wood group setting: WG3, Temperature of testing room: 20 ℃).
그림 Fig. 8. Moisture contents depending on the specimen volume (Condition of environmental chamber: EMC 12 %, Conditions of density setting for MC-380XCA:500kg/m³, Conditions of wood group and temperature setting for MC-460: WG3 and 20 ℃, Temperature of testing room: 20 ℃).
그림 Fig. 9. Moisture contents detected by dielectric type meters (MC-380XCA) for combinations of specimens which have different moisture content (Conditions of density setting: 500kg/m³, Temperature of testing room: 20 ℃).
그림 Fig. 10. Comparisons of moisture contents depending on measuring methods (Conditions of density setting for MC-160SA and MC-380XCA: 500kg/m³, Conditions of wood group and temperature setting for MC-460:WG3 and 20 ℃, Temperature of testing room: 20 ℃).

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문제 정의

The purpose of this study was to evaluate MCs of wood products using NDT methods dielectric moisture meter and resistance meters. To measure the MCs of domestic wood products more reliably, the effects of setting conditions of the meters and characteristics of materials on MC measurement were analyzed.

제안 방법

4. The four combinations were composed with the two grain directions (radial and tangential) and two MC conditions of contacted surface (12 % EMC and saturated MC).
Jung and Smith (1994) evaluated the EMC of red pine, eastern white pine, eastern hemlock, and Norway spruce dried by conventional kiln dry and high temperature dry. The specimens were equilibrated to 15 % of the target EMC at 25 ℃ (relative humidity: 77 %) and the EMCs of the specimens were determined by using oven-dry method, resistance meter, and capacitive-admittance meter. The measured EMCs of specimens were affected by the species and the applied dry method.
To check the sensitivity of the MC meters by density, the MC of specimen was measured by changing the setting of wood density as 400, 500, and 600 kg/m3 in the meters.
To evaluate the detectable penetration depth of dielectric type meter, four combinations were composed using S-L-30-E (12 % EMC) and S-L-30-S (saturated) specimens (Fig. 4). Four combinations were reflected the grain directions (radial and tangential) and MCs of contacted surface (12 % EMC and saturated MC).
When the electrodes were inserted into the X-Z plane, the electrodes were arranged to the parallel or perpendicular to the longitudinal direction. To investigate the effects of density and temperature on MC measurement, different settings including 4 different wood group options (WG1, WG2, WG3, and WG4) and temperatures of 0, 10, 20, 30, 35 ℃ were used. The temperature of the testing room and environmental chamber was 20 ℃.
To investigate the relationship between the measured MCs and the characteristics of materials, three kinds of wood products, solid wood, glulam, and cross-laminated timber (CLT) were prepared. The wood products used in this study are from larch (larix kaempferi, 560 kg/m³) and pine (pinus koraiensis, 430 kg/m³).
The purpose of this study was to evaluate MCs of wood products using NDT methods dielectric moisture meter and resistance meters. To measure the MCs of domestic wood products more reliably, the effects of setting conditions of the meters and characteristics of materials on MC measurement were analyzed.

대상 데이터

The 90 mm thick CLT was consisted with 3 layers and the thicknesses of all laminas were 30 mm. The 120 mm thick CLT was consisted with 5 layers and the thicknesses of outer and inner laminas were 30 mm and 20 mm, respectively. The last letter indicates the MC conditions of specimens.
To investigate the relationship between the measured MCs and the characteristics of materials, three kinds of wood products, solid wood, glulam, and cross-laminated timber (CLT) were prepared. The wood products used in this study are from larch (larix kaempferi, 560 kg/m³) and pine (pinus koraiensis, 430 kg/m³). Fig.

참고문헌 (18)

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Exotek User’s manual for MC-460 Exoteck instruments 2013c www.exotek-instrucments.com
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원문보기 상세보기
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Journal of the Korean Wood Science and Technology Lee 44 3 424 2016 10.5658/WOOD.2016.44.3.424 Comparison of moisture absorption/desorption properties of carbonized boards made from wood-based panels

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Journal of the Korean Wood Science and Technology Oh 44 1 106 2016 10.5658/WOOD.2016.44.1.106 Electrical properties and far-infrared ray emission of ceramics manufactured with sawdust and rice husk

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Journal of the Korean Wood Science and Technology Ra 42 6 653 2014 10.5658/WOOD.2014.42.6.653 Determination of equilibrium moisture content of outdoor woods by using hailwood-horrobin equation in Korea

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Journal of the Korean Wood Science and Technology Ra 46 4 301 2018 10.5658/WOOD.2018.46.4.301 Determination of moisture index in Korea

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