Failure of a chain link


Case A link from an elevator chain has broken. The link was manufactured from ferritic cast iron and operated under atmospheric conditions for several years. Failure however, caused production downtime and subsequent damage.
 
Cause  
 
Investigation of the fracture surface revealed the failure mechanism "fatigue" as a result of a dynamic stress from one-sided bending load. Initiation had occurred at a location where a geometrical transition coincided with an imperfection caused by the finishing of the component.
 
Advice   Recommendations were given how to inspect the finishing quality of a surface particularly at crucial locations of dynamically loaded components.