29—YARN-BENDING AND THE WEIGHTED-RING STIFFNESS TEST

The standard ring-loop test for yarn flexural rigidity is in error unless the yarn bends linearly. The deformation and recovery behaviour of a ring of yarn is therefore recalculated on the basis of non-linear bending behaviour, in which a coercive or frictional couple must be overcome before the yarn bends linearly. Good agreement between theory and experiment is demonstrated.