Development and Validation of a Model for Operationally Seized Bolted Joints for the Research on Gentle Bolt Disassembly

Abstract

Thread galling and seizure is a major impediment to the disassembly of bolted joints. The near-locking of the joint can result in damage to or even breakage of parts of the bolt when a seized bolt is unscrewed. In maintenance, repair, and overhaul (MRO) of complex capital goods such as aircraft engines, seized bolts result in additional disassembly and repair work. Especially in the aircraft engine's hot-section, joints are vulnerable to seizure and galling due to material pairing and thermal conditions. Extensive investigation of the disassembly of joints seized during operation may not be implemented during maintenance orders. The manufacturer's specifications and aviation safety authorities only permit predetermined tools. Therefore, artificial samples are needed to perform fundamental experiments. In this article, a model for artificially and reproducibly replicating seized bolted joints is presented. By adding and adjusting an external clamping force on the thread, the loosening torque can be adjusted as a function of the additional forces. The statistical evaluation of performed experiments will validate the assumed relationship between clamping force and loosening torque. Therefore, this model provides the basis for further disassembly studies by providing artificial and reproducible samples.