AN INVESTIGATION OF THE SELF-LOOSENING BEHAVIOR OF BOLTS UNDER TRANSVERSE VIBRATION

Although a great deal of research has:focused on the reliability of bo lts, self-loosening, which is a main cause of failure of bolted connec tions, is still not fully understood, To develop a complete model of t he self-loosening behavior of a transversely excited bolted connection , an extensive study of the mechanisms of bolt self-loosening is prese nted here. In this work, the theory of Hertz contact stress is employe d to find a contact stiffness. Using this stiffness with a two-degree- of-freedom dynamic model gives the transverse force applied to the bol t when the bolted connection is subjected to dynamic excitation. This transverse force is found to bean important factor in self-loosening. Based on the results from static and dynamic models, a main cause of b olt self-loosening is found to be impacting between the clamped mass a nd the clamping bolt, and the process of bolt self-loosening is predic ted. This prediction dan be favorably compared to experimental results . (C) 1997 Academic Press Limited.