Maintaining appropriate preload in bolted joints is critical for safe and efficient operation of nearly all built-up structures. Loss of preload during operation typically results either from sustained vibrations at a high enough level that self-loosening occurs over relatively long periods of time or from extreme shock loading where the joint loosens in fractions of a second. Modeling of joint loosening often focuses on the tribological aspects, complex analytical approaches, or high-fidelity numerical simulations using finite element (FE) models. While such approaches may succeed for a single bolt or joint, they are simply unfeasible when simulating the response of an entire built-up structure, which may possess dozens to thousands of joints. Thus, there is a need for reduced-order models (ROMs) that capture the essential physics governing the loosening mechanics of bolted joints, but drastically lower the computational cost of simulating significantly many joints. This research introduces a reduced-order, phenomenological model for the mechanics governing the loosening of axially oriented threaded joints. Specifically, the model introduces a mathematical relationship between the stiffness and torque of the joint and treats the torque as a new, dynamic internal variable governed by a first-order, ordinary differential equation. The physical motivation for the model is presented followed by an application to an experimental study of a split-Hopkinson pressure bar with a threaded joint subjected to extreme shock loading. The application demonstrates the identification of the parameters of the proposed ROM using measured data and validates the procedure through a comparison between the experimental results and a FE model incorporating the identified ROM.


Reduced-Order Modeling of Loosening Mechanics in Axially Oriented Threaded Joints

Division / Sponsors: 
Design Engineering Division and Computers & Information In Engineering Division


Paper Proceedings: https://asmedigitalcollection.asme.org/IDETC-CIE/IDETC-CIE2020/volume/83907

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