Damping in Friction-Grip Bolted Joints

The object of the work reported in this paper is to obtain a measure and an understanding of the damping in high-strength friction-grip bolted joints. Static tests to determine the coefficient of friction and cyclic tests to determine the amount of damping in symmetrical double-coverplated butt joints are described. Four plate surfaces were examined, i.e., galvanized, inorganic zinc silicate, urethane chromate primer, and mill scale. An energy loss relationship was found for each surface type. At the working load levels, the damping factors ranged from 5% to 12%, and the energy losses, after early variations, tended to stable values with increasing numbers of cycles. Suggestions on improvements to increase joint damping are given.