Fatigue failure analysis of a spring for elevator doors

The present work details a study performed for the determination of the causes of the premature rupture of a spring from an elevator door control mechanism. The study is based on the general methodology applicable to failure analysis. The results obtained in the experimental analysis and the analytical calculations lead to the conclusion that the fracture of the spring was caused by a mechanical fatigue mechanism whose origin is related to the presence in the periphery of the material of inclusions and superficial folds (stress concentrators), probably aggravated by the tensional state derived from the lack of alignment in the application of the load on the spring with respect to its axial axis.