AN EXPERIMENTAL AND NUMERICAL INVESTIGATION OF THE COMBINATION OF DIFFERENT DAMPER TYPES FOR IMPROVED CONTROL OF VIBRATION

Abstract

Eliminating and reducing unwanted vibrations required a good knowledge of the dynamic systems fundamental components; mass, spring, and damper. Meanwhile, dampers are responsible for reducing the vibrations amplitudes and the time needed by a structure to reach its steady state. This research is focused on studying a combination of different dampers through computational and experimental approaches. Furthermore, parametric studies are conducted to investigate the parameters that affect each damper's damping behavior. Two dampers were designed, manufactured, modeled, and tested through this study. Firstly, a hybrid damper was developed by integrating two damping technologies; Viscous Fluid Damper (VFD) and Particle Impact Damper (PID). The VFD used in this study was a Mono-tube commercial viscous damper used in the automobile suspension system. On the other hand, the PID part consisted of a circular plastic enclosure filled with Stainless Steel 15mm diameter bearing balls. The Fluid Impact Hybrid Damper (FIHD) was designed by attaching the PID part to the VFD piston rod. A shaker testing setup was developed to drive the hybrid dampers piston rod into a sinusoidal dynamic load with a 1-8 Hz frequency range. The number of balls was changed three times (5, 10, and 15) to examine this parameter effect on the FIHDs damping effect. In addition, a Finite Element Model (FEM) of the FIHD was developed using LS-Dyna explicit solver. The FEM of the FIHD simulated the elastoplastic collisions between the balls and the walls using a piecewise-linear plasticity material model. Results were presented using Frequency Response Function (FRF) to show the damping effect in a set of force-independent results. The evaluated FRF of the two approaches (Experiment and FEM model) showed a noticeable reduction in amplitude at the systems natural frequency (2 Hz). In addition to the hybrid damper, this study also investigated a damper that belongs to the semi-active countermeasures known as Magnetorheological fluid (MRF) damper. MRF dampers damping effect is controlled using a magnetic field produced by an excitation system. In an MRF damper, a smart fluid is used as the damper fluid instead of using the classic hydraulic oil. The excitation system components were designed and manufactured based on dimensions reported in a previous study. The excitation system's magnetic field (MF) density value was obtained both experimentally and numerically using Comsol FE software. The MF study aimed to address the parameters that affect the magnetic field density, and thus, the MRF damping effect. Eventually, a Computational Fluid Dynamic (CFD) Analysis is conducted on the MRF damper. The CFD analysis describes the fluid flow between the compression and rebound champers through the internal orifices. Averaged Navier-Stokes equations are solved by the SIMPLE method, and the RNG k-? is used to model turbulence when the fluid passes through the orifice. The viscosity of the MRF was evaluated experimentally using a viscosity meter when applying different values of magnetic flux. The magnetic flux values were changed along with changing the excitation current values from 0 A to 5 A with a 1 A increment. Rebound and compression forces were observed from the static pressure contour plot. Based on the damping coefficients obtained from different viscosities values, the results showed that the damping values are exponentially increasing when increasing viscosity.