タイヤコードの疲労の研究

第2報 タイヤコードの疲労機構について

抄録

On the observation of fatigued tirecord under a microscope, it was observed that the ruptured fibers applied by the T-type fatigue tester splited longitudinally in several cracks. This phenomena resembles to that of cords fatigued in the tire and proves that the T-type fatigue tester is more proper as a fatigue tester of tire cord.
The mechanism of the flexing fatigue is seemed to be different from that of the stretching fatigue. Therefore, cord must be made from raw yarn having suitable properties according the practical use.
It is desirable to increase the value A and K, obtaining by the characteristic fatigue test. A has meaning of tensile strength, but K has direct relation with H which means the innate elastic properties of yarn. It was found the following relationships: H∞1/K_s and H∞K_f, where K_f and K_s are the value of K respectively in the case of flexing- and stretching-fatigue. The value of A is opposit to that of H; the increases of the value of A (∞K_s) is favor on stretching fatigue. On the contrary, the increase of A (∞1/K_f) and is not favor on flexing fatigue. But by relaxation after stretching in the process of spinning viscose rayon, it can be able to increase the value of K_f, without decreasing the value of A.
Because the values of A of “BX” and “Supra” are great but the values of K_f are small, there fibers are not suitable for tire cord. “Super Cordura” may be said new type of high tenacity rayon having great A and K_f.