MS09.7: Nonlinear Dynamics in Engineering Systems

Steam generators inner tubes wear out over time due to flow induced vibrations and impacts with the support structures. In order to better understand the non-linear response of these structures, a simplified mock-up of a steam generator straight section placed inside a hole with clearance was used to compare numerical results and measurements. These numerical results were obtained using a regularized contact and the harmonic balancing method (HBM), which allowed to calculate the multiple stationary existing responses of the system, as well as the bifurcation points. Parametric bifurcation tracking with respect to the eccentricity of the tube with respect to the annular stop has been carried out.

This research conducts a thorough examination of an innovative mechanical system inspired by recent advancements in metastructures, specifically focusing on Origami-type structures due to their intriguing unique non-linear stiffness. These structures, when appropriately designed, demonstrate Quasi-Zero Stiffness (QZS) characteristics within a specific working range, aligning with the High Static Low Dynamic (HSLD) stiffness concept. This study investigates the vibration isolation characteristics of Origami-type suspensions, emphasizing their potential as low-frequency passive vibration isolators. The Kresling Origami Module (KOM) is chosen for its compactness and compatibility with 3D printers. The investigation includes a detailed study using Finite Element Analysis and an experimental campaign. It explores the influence of geometric parameters on the non-linear Force-Displacement curve. Moreover, multibody dynamic simulations will be presented and confirm low-frequency isolation properties within the QZS region. The research highlights the transformative potential of Origami-type metamaterials in advancing low-frequency vibration isolation technology. Challenges related to material properties and loading mass variations are discussed, providing valuable insights for future developments in this promising field.

The resonant behavior of two systems with a limited power supply (or so-called non-ideal systems) having three degrees of freedom is analyzed. Resonant steady states are constructed by the multiple scales method. The transient is presented using the two-point Padé approximants containing exponentials. Obtained analytical results are compared with a numerical simulation. It is shown that amplitudes of the resonance vibrations of the elastic sub-system can be essentially reduced by changing the system parameters.