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This paper presents an effective way in damage detection of beam structures using the wavelet analysis along with the general beam solution. Two case studies are considered: (1) a clamped beam with a damage point of zero bending moment; and (2) a simply supported beam with a transverse open crack. The proposed method is capable of revealing the precise damage locations which is generally difficult to be identified using the standard eigenvalue analysis.

This paper presents a modified harmonic balance solution method incorporated with Vieta’s substitution technique for nonlinear multimode damped beam vibration. The aim of the modification in the solution procedures is to develop the analytic formulations, which are used to calculate the vibration amplitudes of a nonlinear multimode damped beam without the need of nonlinear equation solver for the nonlinear algebraic equations generated in the harmonic balance processes. The result obtained from the proposed method shows reasonable agreement with that from a previous numerical integration method. In general, the results can show the convergence and prove the accuracy of the proposed method.

An experimental study for the active vibration control of structures subject to external excitations using piezoelectric sensors and actuators is presented. A simply supported plate and a curved panel are used as the controlled structures in two experiments, respectively. The Independent Modal Space Control (IMSC) approach is employed for the controller design. In order to increase the adaptability, the time-domain modal identification technique is incorporated into the controller to real-time update the system parameters. The adaptive effectiveness of the time-domain modal identification technique is tested by fixing an additional mass on the simply supported plate to change its structural properties. The vibration suppression performances of the controller are 5.7 dB and 10.8 dB for the simply-supported plate with/without the mass subject to a chirp sine excitation, respectively. For the experiment of the curved panel subject to a sinusoidal excitation, the vibration attenuation of the control scheme is 5.0 dB even the control circuit is subject to some noise generated by electrical and magnetic interferences.

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