Threaded fasteners continue to find widespread use in machines, structures and mechanisms. Their primary function is to provide a desired preload within a bolted joint. Yet the widely used torque method to achieve preload, based entirely on tightening torque results in excessive uncertainty of +/-35% for unlubricated fasteners and +/-25% for lubricated fasteners.
This technology offers a method and apparatus for achieving a precise preload in bolted joints by utilizing thread pitch, tightening torque, and removal torque measurements. It eliminates the need for pre-existing torque-tension data, thereby reducing uncertainty in preload estimation. The method involves applying a tightening torque to a fastener, measuring the torque required to remove it, and using these measurements along with the known thread pitch to calculate the preload. What differentiates this technology is its ability to provide accurate preload calculations without relying on previously obtained torque-tension data, which is often fraught with uncertainty due to variations in fasteners, tools, and techniques. This approach not only reduces the uncertainty in preload estimation but also accommodates variations in fastener conditions and user technique.
A Torque Wrench Configured to Achieve a Target Joint Preload