海水中に浸漬された網糸の強さの変化について-2-

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In the previous paper reporting changes the strength of cords immersed in the sea, the description was mainly concerned with non-treated synthetic cords. Whereas, the present work deals with tarred synthetic cords subjected to the sea immersion to see relationship between the tensile strength and the testing temperature as well as change in the strength that likely occurs during the immersion. The tarred synthetic cords used include Amilan, Cremona, Kanevyan and Saran. Each of them was categorized, as before, into B1 and B2: the former group being immersed continuously, while the latter intermittently. 1) Among the results obtained Figs. 1 and 2 show relationships between the experimental period and either the tensile strength or elongation along with mean testing temperatures which varied depending on a testing day. 2) In laboratory experiments of the same materials as used for the sea immersion it has been confirmed that tensile strength of the cords may be indicated with function of quadric or a higher degree in relation to the testing temperature. Relationship between tensile strength with temperature S0θ or between elongation with temperature E0θ may be expreseed by an experimental formula, respectively: S0θ=a+bθ+cθ2 3 ?? θ ?? 30 E0θ=a'+b'θ+c'θ2 3 ?? θ ?? 30 From the experiments the constant, such as a, b, c, a', b' and c', were obtained as shown in Table 1. 3) When Siθ represents the tensile strength at θ°C of a tarred cord which has been submerged in the sea continuously or intermittently during i days, change of the tensile strength Ki is measured as Ki=Siθ/S0θ In the same way, change in the elongation K'i is K'i=Eiθ/E0θ 4) Let Kjl represent the mean ratio of changes from the tensile strength as of the i-th day to that on the j-th day after inception of the immersion, then kjl={(Ki-Kj)/(j-i)}×100(%) The mean ratio as to the elongation, k'ji is in the same way k'ji={(K'i-K'j)/(j-i)}×l00 (%) The ratios K and K' are obtained theoretically by dK/di=f(i) & dK'/di= ?? (i) K=K0+∫i0f(i)di & K'=K'0+∫i0 ?? (i)di where f (i) is a general form of k and ?? (i) of k'. 5) So far the experiments have revealed that tensile strength of tarred synthetic cords in general tends to be more affected in summer, than any othor season while the strength of a particular synthetic cord, Cremona, is decreased during summer to fall: however, the change in the elongation of these cords seems uniform throughout the submerging perind.
社団法人日本水産学会の論文

海水中に浸漬された網糸の強さの変化について-2-

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