Frictional Behaviour
Intermittent sliding behavior between surfaces in contact under varying frictional forces represents a complex physical state in drawing zones. During the wet spinning of flax, stick-slip dynamics govern the movement of fibres past each other as they are drawn through the drafting zone. This phenomenon occurs because the static friction between wet fibres is higher than the dynamic friction, causing a repetitive cycle of gripping and releasing.
This alternating motion produces localized variations in yarn thickness that can weaken the finished product.
Drafting Process
Controlling this cyclical friction involves modifying the temperature of the water bath to change the viscosity of the liquid film between the fibres. This thermal adjustment alters the duration of the sticking phase, which in turn minimizes the severity of the stick-slip dynamics. When the fibres slide more smoothly, the resulting yarn has a more uniform density and higher tensile strength.
Spinning mills rely on these temperature adjustments to ensure consistent yarn quality from varying batches of raw flax.
Velocity Limit
High drawing velocities prevent the establishment of the sticking phase, thereby transitioning the system into a continuous sliding regime. When the drafting speed exceeds a specific threshold, the rapid movement of the fibres does not allow the static bonds to reform. Yarn uniformity is therefore optimized by operating above this transition point while staying within the mechanical capabilities of the machine.
