Implementation of a bolted joint model in Modelica

Abstract

The basic mechanics of a bolted joint are well-known and have been studied for a long time. The dominating principle is to represent the parts in a joint as a series connection of linear compression and tension springs. However, traditional models often neglect the tightening dynamics and their interrelation with, for instance the friction or embedment. To study these phenomena further and determine their impact on the tightening process and dynamics, and for developing new tightening control strategies, it is necessary to model a threaded fastener and implement it in a suitable simulation environment.Existing models and experimental data have been studied to find equations that fit the observed behavior. Novel models were combined with standard Modelica components to form a threaded fastener model. The simulation results were compared with tightening data from experiments. This work proposes new models for the first three tightening phases, embedment, and threaded fastener friction. These models are implemented in the modeling language Modelica. The results show that it is possible to resemble a typical threaded fastener tightening with power tools. The friction and tightening phases show the expected behavior, while the embedment model needs further experimental verification. During modeling, the model is susceptible to the chosen parameters. Parameters for the joint stiffness, obtained via the VDI guidelines, needed to be reduced by 30% to resemble the joint in a dynamic simulation.