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改良した立木曲げ試験によって測定した造林木の樹幹ヤング率の検証

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Title: 改良した立木曲げ試験によって測定した造林木の樹幹ヤング率の検証
Other Titles: Verification of Trunk Modulus of Elasticity Obtained by Improved Tree Bending Tests
Authors: 日置, 絵里香1 Browse this author
小泉, 章夫2 Browse this author →KAKEN DB
佐々木, 義久3 Browse this author →KAKEN DB
鳥田, 宏行4 Browse this author
Authors(alt): Heki, Erika1
Koizumi, Akio2
Sasaki, Yoshihisa3
Torita, Hiroyuki4
Keywords: nondestructive test
modulus of elasticity
coniferous plantation
stress wave velocity
longitudinal vibration
Issue Date: 2018
Publisher: 日本木材学会 The Japan Wood Research Society
Journal Title: Mokuzai gakkai shi : 木材学会誌
Volume: 64
Issue: 3
Start Page: 115
End Page: 121
Publisher DOI: 10.2488/jwrs.64.115
Abstract: 立木のヤング率を測定する非破壊試験の一つとして立木曲げ試験法がある。その測定精度の向上を目指して,現場で荷重変位関係を表示し直線域の存在を確認して樹幹ヤング率を計算するように測定方法を改良した。この改良によって風や隣接木との接触などの影響を容易に排除できることが確かめられた。また,トドマツ,カラマツ,グイマツ雑種F1 の3樹種について,樹幹ヤング率を応力波伝播速度試験や丸太の縦振動試験の結果と比較して,その実用性を検討した。その結果,樹幹ヤング率は供試木を伐採して得た丸太の動的ヤング率との相関が高く,実用的な材質指標として使えると考えられた。縦振動試験によって求めた丸太の動的ヤング率は樹幹ヤング率より30%程度,小さな値となった。その理由の一つとして,樹幹ヤング率では外縁部に形成された成熟材部の高いヤング率が影響して縦振動試験によるヤング率より大きくなったことが考えられた。
The tree bending test is a non-destructive method for evaluating the Young's modulus (modulus of elasticity, MOE) of a tree trunk. We attempted to improve the method to obtain increased accuracy of the estimated MOE. In the proposed method, the load-deflection relationship was graphically displayed on a tablet PC, and the MOE was calculated using the linear section of the load-deflection relationship. As a result, errors caused by wind pressure or contact with neighboring tree crowns could be easily eliminated. The proposed tree bending tests were conducted at plantations of todomatsu (Abies sachalinensis), karamatsu (Larix kaempferi), and larch hybrid. The calculated trunk MOEs were compared with the results obtained from stress wave velocity measurements of the trunks, as well as dynamic MOE obtained by longitudinal vibration tests of the logs harvested after the tree tests. The correlation between the trunk MOE and the dynamic MOE for logs was found to be as high as that obtained for the correlation between the square of the stress wave velocity and the log MOE. The results demonstrated that the trunk MOE obtained by the proposed tree bending test could be used as a practical reference index for the mechanical properties of the wood. The dynamic MOE for log specimens obtained by the longitudinal vibration tests was approximately 30% lower than the trunk MOE. This could be partially explained by the high MOE of the mature wood formed at the outer part of the trunk, which might affect the trunk MOE.
Rights: © 2018 一般社団法人 日本木材学会
© 2018 The Japan Wood Research Society
Type: article
URI: http://hdl.handle.net/2115/70993
Appears in Collections:農学院・農学研究院 (Graduate School of Agriculture / Faculty of Agriculture) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 小泉 章夫

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