Relationship cell wall defomations and mechanical properties of sugi and hinoki woods damaged by typhoon

The purpose of this study is to clarify the effect of compression creases on mechanical properties of woods damaged by typhoon. Sugi (Cryptomeria japonica) trees from seedling and two cartivars (kumotohshi and yabukuguril and hinoki (Chamaecyparis obtuse) trees were examined in this study. The results were summarized as follows; 1) macroscopic compression creases were occured in the stem of seedling sugi and cv. kumotohshi and hinoki, and in many cases comcentrated on one side of the stem. These were distributed up to 2/3 height of the tree from the ground level and marked at 1/4 to 1/3 height (Fig. 2 and Fig. 3). In addition to macroscopic compression creases, microscopic fractures were distributed widely in the tracheid cell walls in the compression crease side of the stem (Fig. 4) 2) White-colored spots were observed on the under side surface of cv. yabukuguri stem bended by typhoon. Trust-lines and slip planes were found in the tracheid cell walls in the under side of the stem (Fig. 5). 3) It was experimentally clear that mechanical properties of small specimens were influenced markedly because of macroscopic compression creases and also affected by microscopic fractures but not as remarkably as macroscopic compression creases (Table 1 and Table 2). 4) In most cases load-deflection or stress-strain curves in the specimens including macroscopic compression creases or microscopic fractures did not show simple line in the range of low load (Fig. 6 and Fig. 7).台風19号の被害を著しく受けたスギ, ヒノキの折損木, 湾曲木および残存立木を対象に, 損傷の発生状況を観察し, ついで小試験体を用いて曲げ試験と縦圧縮試験を行った. 1) スギでは品種間でもめの発生状況に差異がみられるものの, ヒノキ, スギとも肉眼的にもめが認められるとき, 多くの場合, もめは樹幹の片側に集中して発生し, 根元付近から樹高の約2/3の高さまで分布していた. また, もめの程度は樹高の約1/4～1/3の高さで著しかった. 2) ヒノキ, スギとも樹幹のもめ側・白色斑側では, 一見正常にみえる部位にも仮道管壁に顕微鏡レベルの損傷(しわ)が確認された. 3) もめの存在は木材の力学的性質を低下させることが実験的に明らかになった. また, もめほど著しくはないが, 顕微鏡レベルのしわもヤング率と強さに影響をおよぼすことがわかった. 4) 肉眼的な規模のもめや顕微鏡レベルのしわが木材中に存在するとき, 低荷重域での荷重とたわみ(応力とひずみ)の関係は, 単一の直線関係にならない場合が多かった