DPT Vaccine Shortage A Long-Term Headache

Abstract

Although a great deal of research has focused on the reliability of bolts, self-loosening, which is a main cause of failure of bolted connections, is still not fully understood. To develop a complete model of the self-loosening behavior of a transversely excited bolted connection, an extensive study of the mechanisms of bolt self-loosening is presented here. In this work, the theory of Hertz contact stress is employed to find a contact stiffness. Using this stiffness with a two-degree-of-freedom dynamic model gives the transverse force applied to the bolt when the bolted connection is subjected to dynamic excitation. This transverse force is found to be an important factor in self-loosening. Based on the results from static and dynamic models, a main cause of bolt self-loosening is found to be impacting between the clamped mass and the clamping bolt, and the process of bolt self-loosening is predicted. This prediction can be favorably compared to experimental results.