Theoretical solution for allowable minimum wrap angle of strip coil to avoid loosening against expansion force from mandrel

摘要

The critical wrap angle required to avoid loosening of the wrapped strip during coiling without support (wrapper or unit) rolls is solved theoretically by considering the backward tension and the friction force between the mandrel and each wrapped coil layer. The moment just after separation of support rolls form the coil is analyzed. Balance equations for both radial and tangential force on each wrapped layer are derived and solved for tension and contact pressure from the coil end to the strip head in tangential direction. From the results, the allowable minimum wrap angle is determined using known mandrel expansion force, friction coefficient and backward strip tension.