釘の尖端角が保持力に及ぼす影響
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概要
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Wood used: TSUGA (T. Sieboldii CARR.), size 100×100×200 (mm) some properties are shown in Table 1. Nail used : three kinds of usually commercial ones with rolnd shank, points of which were worked to be cone. Fig. 1 Diameter of nailshank and angle of tip are shown in Table 2. Method of driving: Nails are driven into tangential plane from heart side by dropping repeatedly the weight from 20 cm height. Method of withdrawal: by an AMSLER'S universal testing machine, attaching the special chack for withdrawal Results obtained 1. Relations between tip angle and amount driven into are shown in Fig. 2. For the threw curves in upper part ordinate l1 is the length driven into by a constant energy, which is the amount deducted the length (Δl+δl) driven into by the first dropping from the total length (l+Δl) And for the ones in lower part l1 are the length driven into by the first dropping. 2. Relations between tip angle and max. holding power are shown in Fig. 3. The ordinate P/la, rkg/cmi is the mean holding power per unit length. P: max. holding power la: modified length driven into, that is la=l+2-rcota=l+1/2Δl Consideration. The resistance R to driving is composed of the frictional resistance T of shank and the resistance D for pushing aside wood substance of point part. R=T+D T decreases rapidly and becomes constant value as shown in Fig. 3. with the increasing of 2α. On the other hand D increases more gradualy than T decreases, and keep increasing even if T becomes constant. Thus the curves in Fig. 2 are understood. Reference: An Experiment about Nail Holding Power by F. MURATA, H. SuunsAnA & S. KADTTA Trans. of the 61th Meeting of the Jap. Forestry Soc. Apr. 1952 p. 216/218 (in Japanese with english résumé)
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