Effect of Coating Thickness on the Friction Coefficients and Torque-Tension Relationship in Threaded Fasteners

Abstract

This paper experimentally investigates the effect of coating thickness on the thread, bearing friction coefficients and torque-tension relationship in threaded fasteners. The torque-tension relationship is highly sensitive frictional changes. Two different coating thicknesses are investigated using two bolt sizes; realtime test data is collected for two ranges of bolt tension. The experimental set up collects real-time data on the tightening torque, bolt tension, and the corresponding reaction torque. Test data is used for calculating the thread and bearing friction coefficients, as well as the overall torque-tension relationship for two different coating thicknesses. The study would provide an insight into the variation of the torque-tension relationship which is a key factor that significantly affect the reliability and safety of bolted assemblies in many mechanical and structural applications.