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

  • Pang, Sung-Jun (Department of Wood Science and Engineering, Chonnam National University) ;
  • Jeong, Gi Young (Department of Wood Science and Engineering, Chonnam National University)
  • 투고 : 2018.10.01
  • 심사 : 2018.12.21
  • 발행 : 2019.01.25

초록

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 %).

키워드

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Fig. 1. Types and orientations of specimens.

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Fig. 2. Procedures for conditioning and measuring of moisture contents of specimens.

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Fig. 3. Schematic diagram to measure the moisture contents of specimens by using portable moisture meters.

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Fig. 4. Combinations of specimens for evaluating the detectable depth of meters.

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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 ℃).

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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 ℃).

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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 ℃).

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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 ℃).

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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 ℃).

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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 ℃).

Table 1. Nomenclatures of specimens depending on the specimen conditions

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