Finite Element Study on Pre-Tightening Process of Threaded Connection and Failure Analysis for Pressure Vessel

Abstract

Bolt connection is an important part of pressure vessel and plays a very important role in its normal operation. Proper preload should be provided for pre-tightening of the threaded connection. In this study, precise three-dimensional finite element models of bolt and nut have been established, considering helix angle for threaded connections. Pre-tightening process was simulated using ABAQUS to obtain relation curves of tightening torque and preload. Results obtained through finite element method agree well with the theoretical ones with the error within 5%. Then contact stress distribution on contact surfaces of threaded flanges under preload and work load was analyzed. Finally, the effect of friction coefficient of engaged threads and contact surface between nut and flange on tightening torque coefficient was studied. The results show that the friction coefficient of contact surface between nut and flange has great impact on tightening torque coefficient. The results will help to determine the tightening torque for target preload in the pre-tightening process of threaded flange.