Failure analysis of rolling mill stand coupling

• The failure analysis of two slipper coupling is presented.
• Both couplings fractured as a result of fatigue.
• Fractures are caused by deficient design of fillet between paddle and coupling body.
• Redesign of coupling by stiffener between the paddle and the coupling body improved lifetime.

The failure analysis of two slipper couplings showed that both couplings fractured as a result of fatigue. In both cases, the fracture started in the corner between the paddle and the coupling body and propagated around the corner. Both fractures are caused by deficient design of the fillet between the paddle and the coupling body with high stress concentration. In order to extend actual service life, three design modifications have been considered. Numerical analysis showed that redesign of coupling by stiffener between the paddle and the coupling body reduces maximum local and actual service life of couplings can be improved from finite to infinite.