Torque-angle formulation of threaded fastener tightening

In this paper the evolution equations of the bearing and thread friction coefficients are proposed based on mechanical behavior of the bolted joint assembly. The study shows excellent correlation between the proposed model and the experimental results for the breakaway torque values in both the tightening and loosening directions. Evaluation of the torque-angle control of the tightening process is made, and a modified torque-angle control approach is proposed. The effect of friction coefficients on the error in the clamping force prediction is analyzed.