針葉樹材単一仮道管の引張破壊過程

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The purpose of this study is to reveal the fracture process of the single coniferous tracheids under tensile stress and the mechanical behaviour of two kinds of bordered pit, i. e. the cross field pit and the intertracheal pit. The early and latewood single tracheids prepared from the delignified wood chips of SUGI (Cryptomeria japonica D. Don) were freeze-dried, and mounted on the specimen tabs. The single tracheids were stretched after setting on the tensile device. The behaviour of the single tracheid in stretching within the SEM column was observed with a monitor television and recorded on a video tape recorder. Furthermore, the broken ends of the single tracheids were investigated in detail using the SEM. The results obtained from these observations are as follows ; The initial crack of the single tracheid almost always took place at the cross field pit near the end of ray crossing (Figs. 3-2, 5-1, 6-2 and 7). In earlywood tracheids, the initial crack propagated across the cell wall of the ray crossing, accompanying a twist. around the cell axis(Fig. 3-2). The broken end of fractured S_2 layer caused by the initial crack propagation showed the minute splintery mode, indicated by an arrow in Fig. 5-2, because the S_2 microfibrils should have been severed with some slippage among them. Furthermore, the crack sometimes propagated longitudinally along the cell corner (Fig. 4). The initial crack of the latewood trachcid propagated almost perpendicular to the cell axis, and the initially fractured surface of the S_2 layer was very smooth (Fig. 7). In both the early and latewood single tracheids, the fractured wall occurred at the final stage of fracture process showed conspicuously the long splintery mode (Figs. 3-6 and 6-4), indicating the intermicrofibril slippage. The initial crack scarcely occurred at the intertracheal bordered pit. In earlywood tracheids, the intertracheal pit makes resistance to crack propagation in the cell wall, and so the crack ran around the pit margin (Fig. 10). In latewood tracheids, the pit border split along the S_2 microfibril orientation, but the layer in which the microfibrils oriented concentrically was unbroken (Fig. 11) .
社団法人日本材料学会の論文
1975-09-15

針葉樹材単一仮道管の引張破壊過程

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