F-0302 Improvement of Bending Fatigue Strength in Helical Cords

Abstract

The fatigue failure in helical cords is initiated by the shearing stress along stranded glass filaments, which stress is caused by the bending of the helical cord. In this study, the authors propose a parameter S_f=Rr/(scos α) to estimate the resistance of the bending fatigue failure basing on our mechanical analysis. Then, the authors carried out bending fatigue tests by using five types of test pieces, of which the geometrical factors, such as helix angle and radius of strand, are controlled. The fatigue failure resistance is well estimated using S_f. The fatigue failure is hard to initiate in the test pieces with small S_f