Fatigue Failure Mechanism of Steel Cords in Synchronous Belt

Synchronous belts are widely used as a power transmission element in many industrial equipments. The construction of the belts is a rubber and a helical cord as a tension member in the belts. The purpose of this study is to investigate the fatigue failure mechanism of the synchronous belts using steel cords. The steel cord focused here is 1*19 construction, that is made twisting nineteen steel wires. At first, the fatigue failure initiation site was found observing the failure morphology and measuring the belt deformation. Then, the fatigue failure mechanism was discussed with some fatigue tests of the steel cords and any mechanical and finite-element analysis. The belt failure was initiated near the tooth root, where the steel cords were fatigued. The belt curvature was measured by using the deformation of the marker lines that were put on the side surface of the belt. The belt was bent largely near the tooth root under high belt tension conditions. Namely, the belt was damaged by the bending fatigue near the tooth root. Then, the bending fatigue of the steel cord was tested and discussed the fatigue failure mechanism. The fatigue failure was firstly initiated in the outer layer wires. However, the bending stress was lower in the outer layer wires than in the core wire, according to a simple geometrical analysis. It is necessary to consider the initiation of another type of stresses based on the contact between the wires. Therefore, the finite-element was analyzed. We discussed the stress component that accelerated the fatigue failure in the outer layer wires. The friction force that was initiated between the wires well explained the acceleration of the fatigue failure in the outer layer wires.