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The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus >
No.44 (1997/12) >

Title :応力緩和およびクリープにおける応力レベルのスギ材 Slip plane への影響
Title alternative :Effects of stress levels in the stress relaxation test and the creep to slip planes of SUGI wood
Authors :林, 弘也
繁政, 弘造
金城, 一彦
屋我, 嗣良
Authors alternative :Hayashi, Hiroya
Shigemasa, Kouzou
Kinjyo, Kazuhiko
Yaga, Shiryo
Issue Date :1-Dec-1997
Abstract :木材は繊維軸方向の圧縮応力により, Slip planeを細胞壁に発生し, Slip planeは細胞壁の塑性的な変形であり, 偏光顕微鏡により光学的に検出される。Slip planeはひずみ量, 応力との関係を解明することによって, 木材の破壊過程に基礎的な知見を与えると考えられる。木材の破壊過程は, 細胞の構成, 細胞の構造が相互に作用し合い複雑な過程を辿っており, 仮道管壁のSlip planeは破壊応力の20-30%の応力レベルから発生すること, 細胞壁の部位によって同じ応力レベルでも発生数が異なることなどが明らかにされている。本報告は応力の発生状態のSlip planeの発生状態に対する影響を実験的に検討した。針葉樹スギ(Cryptomria japonica)材の成熟材仮道管を対象に, 圧縮応力緩和, 圧縮応力クリープを起こさせ, 応力レベルとSlip planeの発生状態を検討した。実験対象の仮道管壁は晩材の接線壁である。静的強度試験では, Slip planeの発生数が, 既報^<4)>のように応力に対し指数関数的に増加し, 正常状態の試験片であることが確かめられた。(Fig.2)静的強度試験と応力緩和試験とのSlip planeはほぼ同数である。クリープ試験では静的強度試験の1.5-3.0倍発生した。(Fig.4)応力緩和試験のSlip planeは静的強度試験のSlip planeと正の相関関係(Fig.3)にあり, 応力緩和過程に新たなSlip planeは発生せず, Slip planeのひずみ量がわずかに増大して応力を緩和していると考えられた。クリープ過程のSlip planeの静的強度試験のSlip planeの発生数の数倍になり, クリープひずみは新たなSlip planeを発生していると考えられる。クリープ過程のSlip planeはSlip planeを発生する応力レベルに影響されることが推定された。負荷状態が応力やひずみと同じくSlip planeの発生時に影響していることが確認された。
The compression of wood parallel to the grain causes progressive structural deformation in the tracheid cell walls known as slip planes and compression creases. Slip planes were the non-elastic deformation of the tracheid cell wall and detected by a polarizing microscope. By the explanation of the slip plane occurrence related to strain and stress of a solid wood, it is expected to get basic information on the destructive process of a solid wood. It was cleared some points on the natures of slip planes. Slip planes were affected by a cell kind and a structure of cell wall. And slip planes began to occur at the stress level of 20-30% to breaking stress and it occurred locally in a cell wall. In this study, it was discussed the number of slip planes to some kinds of stress at some stress levels to breaking stress. Compression stress applied to coniferous wood SUGI (Cryptomeria japonica) and slip planes were detected on the tangential wall of tracheid in late wood. Applied compression stress was static compression stress, stress relaxation and creep of compression stress. At first, a specimen was examined by naked eye and was checked the occurrence state of slip planes by the static compression test. A SUGI specimen of the static compression test occurred slip planes exponentially to stress levels in normal way. (Fig. 2) Slip planes in the stress relaxation test occurred in the same manner as the static compression test to stress levels. But in the creep test, slip planes occurred 1.5-3.0 times as many as slip planes in the static compression test. (Fig. 4) It was recognized a positive correlation between slip planes in the static compression test and slip planes in the stress relaxation test. (Fig. 3) From this fact, it was considered to be one proof that a stress relaxation came from a expansion of each slip planes occurred in the static compression. On the other hand, slip planes in the creep test were occurred 1.5-3.0 times in the static compression test and a creep strain was occurred new slip planes. In the generating process of a creep strain, slip planes were correlated exponentially to applied stress. (Fig. 5) And it was considered that slip plane occurrence in this process depended on a applied stress level and a creep time. It was recognized that occurrence of slip planes were affected by the applied stress level and the applied method of stress to solid wood.
Type Local :紀要論文
ISSN :0370-4246
Publisher :琉球大学農学部
URI :http://hdl.handle.net/20.500.12000/3719
Citation :琉球大学農学部学術報告 = The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus no.44 p.307 -312
Appears in Collections:No.44 (1997/12)

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