A shaft taken from a mill transfer chain that was frequently
overloaded,cause the shaft to fail by torsion shear. What type of
replacement shaft will solve the problem? What different mechanical
properties must it posses so it will not again fail by torsion shear?

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Clarification of Question by wonderingbrain-ga on 13 Dec 2005 11:13 PST

the case is about a shafting taken from a mill transfer chain that was
frequently overloaded., causing the shaft ( made of low carbon steel)
to fail by torsion shear. It has obviously been loaded in torsion
beyond it's elastic limit into the plastic range and has taken a
permanent set. Since the sprocket and bearing bores are not easily
changed to substitute a larger diameter shaft, what type of
replacement shaft will solve the problem? What different mechanical
properties must it posses so it will not again failby torsion shear?

Find a new shaft that has a high enough ultimate strength to withstand
the forces you're putting on it?

By torsion shear do you mean a fracture that's perpendicular to the
surface that was under pressure?