Experimental Damping Estimation of Material by Sinusoidal Base Excitation

The material damping, which means energy dissipation in materials under cyclic loading, is an important design consideration for vibrating structures especially in the airplane and automobile engineering. The main objective of this work is to determine natural frequency and damping ratio by sweep sine test and half power bandwidth method respectively. Aluminium Beams of required size are prepared and are excited using an Electro-Dynamic Shaker excitation technique over the frequency range of 5-500 Hz. The modal analysis of the beam is also done on ANSYS platform as well as theoretically. A good concurrence for natural frequency is found in all these three methods. Based on the experimental results, damping ratio is determined by using half power band width method. The effect of three major geometrical parameters on material damping is also investigated. For this purpose, Design of Experiment (Taguchi L9 orthogonal Array) is performed to find the parameters combination to give the optimum damping ratio. Analysis of variance (ANOVA) and S/N (signal to noise) ratios analysis is also performed. The results show that the amplitude of excitation significantly affects the damping ratio. It is also found that the predicted results obtained using regression equations are in good agreement with experimental observations.