静的くり返し曲げ荷重を受けた木材の力学的な挙動と細胞壁の観察

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静的な単一の曲げ荷重と、くり返し曲げ荷重を受けた木材はりについて、1)荷重を受けているときに生じる木材の細胞壁の変形、2)荷重が取り除かれたあとの細胞壁の変形の回復状態について、走査電子顕微鏡による観察を行った。さらに、3)荷重を受けたとき木材細胞壁に生じたmicroscopicな破壊と、木材の力学的挙動との関係についても検討を加えた。木材が比例限荷重よりもはるかに小さな曲げ荷重を受けたときでも、木材はりの圧縮側縁面の早材部細胞壁にわずかながらシワ状の変形を残し、すでに細胞壁の破壊が始まっていることが認められた。また、この除荷後にも認められる細胞壁のシワは、木材の残留変形と密接に関係することがわかった。Although many papers and reviews on the mechanism of fracture in wood have been reported by a number of researchers, there are still problem areas. Hence, the purpose of this study is to investigate： 1) the microscopic failure in the wood cell wall, which is due to repeated bending load, 2) the effects of loading levels on cell wall damage, and 3) the relationship between the cell all damage caused by loading and the mechanical behaviour of wood. The cell walls of the wood specimens were continuously observed during repeated bending, employing the techniques of scanning electron microscopy with filmy (acetyl cellulose) replica method. The test specimens were prepared from SUGI (Cryptomeria japonica D. Don) -wood and were conditioned to 12% M.C. The results of the electron microscopic observations are summarised in Table 1. The wood subjected to bending loads less than the proportional limit exhibited microscopic crease-like compression failures (Fig. 3). These occurred to a slight degree in the cell walls in earlywood on the compression side of the wooden beams. These microscopic compression creases in cell walls were very closely correlated to the residual deformation of wood.
日本木材学会,The Japan Wood Research Societyの論文

静的くり返し曲げ荷重を受けた木材の力学的な挙動と細胞壁の観察

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