Study of Vibration Characteristics of Different Materials by Sine Sweep Test

Abstract

Estimating damping in structures made of different materials (steel, brass, aluminium) and processes still remains as one of the biggest challenges. All materials possess certain amount of internal damping, which is manifested as dissipation of energy from the system. This energy in a vibratory system is either dissipated into heat or radiated away from the system. Material damping or internal damping contributes to about 10-15 % of total system damping. The main objective of this thesis is to estimate the damping ratio, natural frequency of aluminium, brass, and steel by forced vibration analysis experimentally and verify theoretically. Cantilever beams of required size and shape are prepared for experimental purpose and the damping ratio is investigated. Damping ratio is determined by sweep sine test using half power bandwidth method. Forced vibration tests also confirmed the damping ratios obtained by sweep sine method. It is observed that damping ratio is higher for steel than brass than aluminium. This thesis presents results of an experimental forced vibration analysis of beams made with different materials such as Steel, Brass, and Aluminum. The beams were excited using an electodynamic shaker excitation technique over the frequency range 5-50 Hz. Frequency response functions (FRFs) were obtained using OROS vibration analyzer. The FRFs were processed using NV Solutions analysis package to identify natural frequencies and Damping ratio of the cantilever specimens for each material.