Imposing Node on Linear Structures During Multi-harmonic Excitations

Vibration absorbers are usually designed using the Finite Element (FE) model of structures. However, the FE models of structures are not always precise due to inaccurate estimation of the physical properties of structure, discretization errors of distributed parameters, poor approximation of boundary conditions, inadequate modeling of joints and computational errors. In contrast, modal testing is an experimental approach to build the mathematical model of structures. As the test structure is modeled by direct measurement on the structure, the modal models are more accurate than FE models. In this paper, a method is proposed to impose node on an arbitrary point of a linear structure subjected to a multi-harmonic excitation by attaching two spring mass absorbers. The method is based on the structural modification Using experimental frequency Response Functions (SMURF) technique and estimates the mass values of the absorbers for the suggested stiffness values. The advantage of this approach is that there is no need to have the theoretical or FE models of the structure and it is not restricted to a particular geometry. A cantilever beam subjected to multi-harmonic excitations is considered as a numerical case study in a simulated test and the sprung masses are designed to suppress the vibration amplitude of the beam at a selected arbitrary point.