Fretting wear is the main cause of Stage-2 continual bolt self-loosening. A parameter that causes wear loss in the bolted joint load path results in bolt self-loosening. Contact between washers and the nut/bolt head contributes the most to the bolt self-loosening.

Initial wear independent pretention loss occurs only in the initial stage. After settling time, initial pretention loss is constant. The initial loss depends on the magnitude of the excitation.

Direction of the excitation is a critical factor for bolt self-loosening.

Bolted-joint natural frequency for a given pretention load is captured well with a simplified bolt thread model. If the excitation frequency is close to the natural frequency, non lateral loading might cause pretention loss.

The simplified bolt thread model and adaptive scaled wear formulation are computationally effective for modeling the bolt-self loosening.