Different Torque Settings and Their Effect on the Vibration Characteristics of a Bolted Structure

Abstract

The vibration characteristics of a bolted structure are very sensitive to the preload applied when the bolts are tightened. This study investigates how different torques affect the vibration characteristics of a bolted structure. The structure consists of two beams connected by two bolted joints. This study is conducted using different tightening configurations: self-tightening, hand-tightening and different torque values between 1 Nm and 15 Nm. Based on the configurations, the frequency response functions (FRFs) of the structure obtained from experimental modal analysis (EMA) are observed to analyse the changes in the vibration characteristics of the structure. Shaker testing is performed on the structure under free-free boundary conditions. A FE model of the structure developed is used to calculate the natural frequencies and mode shapes, which are used for validation. A comparison between the natural frequencies of FE and EMA shows that they increase with increasing torques. The comparison also shows that the 8th mode, which is a torsional mode, is more sensitive to torque changes compared to other modes. Another striking finding of this study is that a decrease in damping values with increasing torque is observed in the experimental FRFs of the structure. The results of this study show that different torque settings lead to different vibration characteristics of the structure.