The Role of Vibration-Induced Settling on the Normal and Tangential Forces within a Jointed Structure

Abstract

When testing the vibrations of jointed structures, it is common practice to perform repeated runs until the behavior stabilizes and only report the final results. The purpose of the present work is to understand the transient settling phase and to establish a correlation between residual traction (static tangential force) at the interface, preload values, and the vibration response of the jointed structure. An L-beam coupled with a cross-beam is considered, which was originally designed to study the effect of residual tractions on bolted joints, as non-unique residual tractions significantly affect the vibration response of friction-damped structures. The contact interfaces are deliberately positioned orthogonal to each other to achieve tangential-normal coupling. A side load mechanism is added to change tangential forces to reach different static equilibria in the system. It is observed that the static equilibrium varies significantly during the first few vibration tests following the assembly and is marginally affected by the designed mechanism. The settling phase is experimentally analyzed with regard to tangential friction forces, bolt preload values and amplitude-dependent modal parameters. The initial normal and tangential contact forces, observed immediately after assembly, are affected by the misalignment induced by manufacturing and wear. Subsequently, well-repeatable behavior is observed in terms of the amplitude-dependent frequency and damping ratio of the fundamental mode. The results of this research provide novel insights into the physics of how interfaces settle. Recommendations for avoiding bolt loosening are made based on the observations of this research. © 2025 Elsevier Ltd