Modeling Self-loosening in Bolted Joints

Bolt self-loosening is a phenomenon that can occur in various types of fastenedjoints. Joint compliance, bolt geometry, and external loading can allcontribute to conditions where self-loosening can be observed. Understanding the mechanisms that contribute to self-loosening will lead to higher product confidence and reduced development costs for new product introductions. Self-loosening of threaded fasteners has been studied extensively both analytically and physically. In one of the foundational publications on this subject, Junker concluded that self-loosening occurs when relative movement occurs between the thread and head of a fastener. Bending forces, prevailing torque, and friction present in joints with transverse motion all combine to loosen fasteners. Analytical methods have been used to improve upon this understanding, with each successive study contributing to enhanced simulation capabilities. The study presented here sought to build upon these learnings to provide an enhanced understanding of the physics involved in bolt self-loosening.