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Scientia Silvae Sinicae ›› 2013, Vol. 49 ›› Issue (7): 129-135.doi: 10.11707/j.1001-7488.20130719

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Effect of White Birch Disk Characteristics on Drying Check Behaviors

Zhao Jingyao, Cai Yingchun, Fu Zongying   

  1. School of Material Science and Engineering, Northeast Forestry University Harbin 150040
  • Received:2012-08-29 Revised:2013-02-13 Online:2013-07-25 Published:2013-07-23

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Abstract:

This paper was carried out to study the characteristics of white birch (Betula platyphylla) disk drying checks(such as the position, MC of check formation, morphology)under stepwise decreasing relative humidity and constant temperature of 40 and 60℃ drying conditions. On that basis, the effects of geometrical characteristics of tree disk, namely, growth eccentricity(GE), roundness deviation(RD)and cross-sectional area(S)on drying checks were investigated. The results showed that under the same drying condition, the early formation of checks within disks with different position, diameter and roundness deviation(RD)had a significant difference. Under 40℃ and 60℃ drying conditions, the early formation of checks' average MC value was 43.9% and 45.6%, respectively. The occurrence of checks was earlier under 60℃ than 40℃ drying condition. Also, the early formation of checks' position was on the border between heartwood and sapwood. Under 60℃ drying condition, the position of checks was slightly expansion to inter with heart checks emerging. Although check total length(CTL)and check average width(CAW)under 60℃ were greater than 40℃ drying condition, there was no significant difference under two drying conditions. The number of V-checks was under 60℃ more than 40℃ drying condition, obviously. The roundness deviation(RD)and cross-sectional area (S)were the main factors that effected check total length and V-check. The disks with larger cross-sectional area(S)and more irregular shape were prone to triggering drying checks during the drying process. Therefore, it was necessary that tree disks were sorted by geometrical characteristics prior to drying.

Key words: white birch, disk, geometrical characteristics, drying, check

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