7. Method for estimating the fatigue life of connectors

Connectors are vulnerable to fatigue damage from the vibrations generated by passing pantographs, and a broken lead wire can cause damage to the pantograph among other things. To prevent this occurring a method was developed to predict the fatigue life of a connector.

Strain on the lead wire caused by vibrations is heavily influenced by the spring constant and resonance frequency and the routing of the lead wire. In order to obtain these influencing factors analytically, based on the results from vibration tests on an actual connector, a finite element method model of the connector is made using a single line instead of a wire strand (Fig.1). The vibrations from other components, such as the contact and messenger wire are then added to the model to enable analysis of the strain incurred on the lead wire. This is then combined with the curve showing fatigue life of connector lead wire obtained from fatigue tests (Fig.2) so that it is possible to estimate the fatigue life for element wire rupture.

After estimating the fatigue life of different shaped connectors in relation to contact and messenger wire vibrations in locations where lead wire ruptures on commercial lines had already occurred, results showed that results for the type C connector corresponded closely with the field incident (Fig.3).

It therefore planned to use this method in future to develop high fatigue resistance connectors.