Abstract: Preload directly affects the fastening performance of bolted joints. Existing research results have shown that preload may decline readily when bolted joints are subjected to cyclic transversal vibration. Plastic deformation and rotation loosening have been thought of as the two main causes resulting in the preload decline. The mechanism of preload decline under transversal vibration is revealed further by several sets of finite element simulations. It is found that the stress redistribution is another important cause leading to the preload decline. Then, the effects of stress redistribution, plastic deformation and rotation loosening on the preload decline are investigated. Various conditions of transversal force, friction coefficients and material properties are used in the simulations. Finally, a typical preload decline curve containing three stages is obtained. At last, transversal vibration experiments were performed to verify the reliability of the typical preload decline curve.

Key words: bolted joints, Junker test, loosening, preload decline curve, transversal vibration