Steel–aluminum screw–thread pair tightening mechanism and fastening axial force conversion efficiency

Abstract

During the tightening of bolted connection, the tightening torque of the bolt is converted into its fastening axial force. The magnitude of the fastening axial force significantly affects the reliability and fatigue strength of bolted connections. Herein, a theoretical analysis of the tightening process of bolt connection is conducted using a power exponent hardening constitutive model, and the expressions of the tightening angle–fastening axial force and tightening angle–tightening torque during the tightening process are derived. A fine finite element model of steel–aluminum thread connections that can be used to simulate the actual tightening process considering the detailed thread structure is established. The accuracy of the theoretical formula is verified by finite element method and experiment, respectively. Through finite element simulation and experiment, the correctness of the formula is verified. Further, the conversion efficiency of the fastening axial force of the steel–aluminum screw–thread pair is analyzed by combining finite element analysis and theory. The results show that under the same tightening torque, the conversion efficiency of the fastening axial force can be increased by 6.8%–9.3% by appropriately reducing the friction coefficient of the steel–aluminum threaded connection pair. By controlling the fluctuation range of the friction coefficient, the dispersal error of the fastening axial force can be reduced by 26.9%–36.7%. The angle method is more conducive to improving the connection reliability of the steel–aluminum screw–thread pair than the torque method.