Torque-Angle Tightening: New Theoretical and Practical Approach

Abstract

Static and dynamic capacities of bolted connections are highly dependent on the preload. For this reason, and due to the inaccuracy of torque tightening technology, many other tightening technologies and preload monitoring have been developed. This paper discusses the concept, the theoretical and the practical approach of the combined tightening method called “Torque-Angle Tightening”. It’s an old tightening technology that consists of a first step to apply a snug torque, then to apply a required angle in a second step. It allows for a more accurate preload compared to the torque tightening. VDI2230 gives some values of the tightening factors for many tightening technologies. This paper provides some new formulas that reduce the error level (difference) between the calculated and real introduced preloads in the bolts. It details some best practices to evaluate the required parameters and to apply the tightening operation correctly. Experimental tests and FE analysis are used to evaluate this improvement of the existing formula.