Changes of Mechanical Properties of Wood under an Unstable State by Heating or Cooling

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  • OOI Kensuke
    Research Division of Agriculture, Graduate School of Kyoto Prefectural University
  • WANG Yue
    Research Division of Agriculture, Graduate School of Kyoto Prefectural University
  • ASADA Teppei
    Research Division of Agriculture, Graduate School of Kyoto Prefectural University
  • IIDA Ikuho
    Research Division of Agriculture, Graduate School of Kyoto Prefectural University
  • FURUTA Yuzo
    Research Division of Agriculture, Graduate School of Kyoto Prefectural University
  • ISHIMARU Yutaka
    Research Division of Agriculture, Graduate School of Kyoto Prefectural University

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Other Title
  • 温度の急上昇，急下降による不安定状態下の木材の力学物性の変化
  • オンド ノ キュウジョウショウ キュウカコウ ニ ヨル フアンテイ ジョウタイ カ ノ モクザイ ノ リキガク ブッセイ ノ ヘンカ

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Abstract

In this paper stress relaxation of water-swollen wood was discussed with two conditions of temperature change, i.e. 1) specimens at 20°C were heated rapidly to 30-80°C, and 2) specimens at 30-80°C were cooled rapidly to 20°C. Stress relaxation was measured in the radial direction for 3 hours after the temperature had changed in 3 minutes. In addition, the fluidity of specimens was defined as the amount of change of the relative relaxation modulus (1-Et /E0). The results obtained are as follows :<br>1) When specimens at 20°C were heated rapidly to 30-80°C respectively, their fluidity clearly increased in comparison with the control specimens, which remained at constant temperature for a long time. Accordingly, It is clarified that an unstable state was incurred not only by cooling but also by heating.<br>2) Under cooling condition, the fluidity of specimens increased in proportion to the degree of cooling ; but under heating condition, the highest value of fluidity was at 50°C or 60°C. The reason for this is that the higher the temperature, the faster the dissolution speed of the unstable state.<br>3) The relaxation spectrum on a master curve basis shows that the peak of temperature history specimen was located at a short-time region in comparison with control specimen. The apparent activation energy was calculated from the relationship between the shift factor and the reciprocal of absolute temperature. The dates indicate that the value of control specimen was higher than that of temperature history specimen. Consequently, it is considered that the unstable structure was formed in the cell wall because of temperature elevation.

Journal

  • Mokuzai Gakkaishi

    Mokuzai Gakkaishi 51 (6), 357-363, 2005

    The Japan Wood Research Society

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