網糸と網糸とが擦れ合つて起こる摩耗-I

抄録

Pervious works on the wearing process of netting threads were concerned in friction of thread against solid matters.^1-3) In the present study, the friction between threads of a fishing net itself has been pursued in an attempt at minimizing possibility of ripping damage by improving seaming and other techniques, if any, of netting fabrication.
A modified Duplan wear tester used for the experiment had a wooden ridged runner on which was mounted one of the sample threads, a (Fig. 1). Another thread b was tightly stretched across a by means of a weight w of 500g hanging through pulleys at the end of b. The runner was made to move back and forth on the rails at 24cm/sec with an amplitude of 4.7cm on both side, the threads being rubbed against each other. For wet test, the threads soaked in water were placed beneath a dripping pan. The wearing process of threads was examined by determining the breaking strength of thread a which was reduced according to the increasing numbers of friction until it was splitted by friction under the same tension. The numbers of continuous friction under different loads effective of splitting therad a were tested by changing the weight within a range of 0.25 to 1.5kg. The sample threads consisted of both vegetable and synthetic fibers of various kinds as indicated in Tables 1 and 5; the ranges of temperatures during the test are in Tables 2 and 6.
The results of the tests revealed:
Dry threads of vegetable fibers, such as cotton and ramie, are very resistable against frietion. But when moistened, the durability is reduced for about one quarter of the dry state ( ?? ables 3, 4 and Figs. 2, 3).
In case of synthetic fibers the durability is just in reverse of vegetable fibers as they are found weak when dry but strong when watered. Different durabilities are quite noticeable depending on kinds of synthetic fiber. Threads of polyamid compound are the strongest, while wet threads of polyvinyle compound equal in strength with that of vegetable fiber. Those of vinylidene-chloride are the least durable against friction (Tables 3, 4 and Figs. 2, 3).
In the test of temperature affecting the durability carried out with polyvinyle and vinyli-dene-chloride, a remarkable difference was found depending on temperatures of dripping water. The drips of water at 5°C made the threads about two times more durable than those watered at 20°C. The relationship between w, the tensive weight of the thread b, and n, the number of friction capable of splitting thread a, may be expressed roughly in hyparbolic curves (Fig. 6). But in most ca ?? es of thread, except ramie, the greater the n, or the smaller the w, the greater amount of friction, wn, is required for splitting the thread a (Fig. 7).