Effects of Bolted-Joint Parameters on Axial Tension after Hydraulic Tightening

Abstract

The axial tension remaining in a bolt after the hydraulic tightening is less than the initial tension from the hydraulic load, and the ratio of the residual tension to the initial tension, an effective tensile coefficient, is the most critical factor to securely tighten a pressure vessel. In this study, an analysis model simulating the hydraulic joint processes by using a finite element model was developed to clarify the effects of various joint parameters on the effective tensile coefficient. The analysis model could estimate the effective tensile coefficient within a 5% error compared to the hydraulic tightening experimental results. The simulated results of the analysis model showed that the effective tensile coefficient changed largely depending on the thickness and the surface pressure of the flange, and that the coefficient hardly changed by the height of the nut and the friction coefficient at the bearing surface.