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.