Catastrophic failure of a South Johnstone mill coupling

A No. 1 mill main drive tailbar coupling at South Johnstone mill failed catastrophically during the 1996 crushing season. Subsequent damage to the mill stand and ancillary equipment resulting from. the pressure feeder drive continuing to force-feed cane towards the stationary rolls was significant. The paper reports on the failure and finite element analysis of the fractured coupling. The coupling failed when the stress intensity at an elliptical quarter crack exceeded the fracture toughness of the cast steel. Finite element models incorporating non-linear geometry and material behaviour of the tailbar and the coupling were analysed. The affect of misalignment on contact pressure. aJ;ld stress was also evaluated. In addition fracture modelling of the failed coupling ':Vas carried out to estimate the fracture toughness of the cast steel.