Gripping Mechanism
Clamping devices designed for tensile testing of high-strength yarns use curved surfaces to distribute gripping stresses gradually rather than concentrated at a single point. These testing instruments require specialized capstan jaws to secure the slippery flax fibres during high-force pulls. By wrapping the yarn around a smooth cylinder before clamping, the device avoids premature breakage at the grip edge.
Tension Distribution
Traditional flat clamps often create a high stress concentration where the yarn leaves the holder, leading to false low readings in flax evaluation. Using capstan jaws allows the force to dissipate along the curved contour through friction, which ensures that the specimen breaks in the center of its gauge length. This uniform load distribution is essential for obtaining reproducible data from wet-spun linen yarns.
Spinning laboratories rely on this design to standardise their quality control checks. Because flax is a relatively brittle natural fibre, eliminating local stress concentrations is the only way to measure its true tensile potential.
Operational Protocol
Test operators carefully wind the specimen around the circular guide to establish a reliable grip without introducing twist. Manual execution of this step requires precision to ensure the yarn sits perfectly in the groove of the capstan jaws before the crosshead moves. Proper alignment prevents both premature failures and slippage during the automated testing cycle.
