Research On Damage Detection Methods Of Micro-beams

With the applications of MEMS(Micro-Electro-Mechanical System) expand rapidly, it is dispensable to conduct reliability test for Micro-structure. In this paper simply supported beam was discussed and with the help of modal analysis damage detection methods of micro-structure was studied. Finite elements simulation was applied to finish the modal analysis as well as damage detection of micro-structure.The theoretical model of damaged simply supported beam have been studied firstly, based on this theoretical model and theory of vibration damage detection indices-Teager energy operator(TEO) which was based on velocity mode shapes and Index indices which was based on statistical hypothesis testing was put forward.Then simulation and analysis for the modal parameters of beams with single and multiple damage have been conducted, the relationship between modal parameters and damage indices with different location, length, depth, shape of cracks. The results showed that the damage detection ability of frequency was limited under complicated damage conditions. Satisfactory result have been achieved with the aid of the curves of Teager energy operator and Index under single damage conditions, however when dealing with multiple damages the TEO curve shows better capability than Index indices.Thirdly multiple vibration testing lines have been utilized to show the distribution of TEO and Index on the whole beam, thus the shape and the direction of damage have been determined. The results of this part showed, on one hand the error of damage length acquired by this method is no more than half of the distance of each vibration testing line, therefore to measure the length and direction of damage by this method is feasible. On the other hand the TEO showed better capability than Index indices under multiple damaged conditions.Finally, the anti-noise capability of TEO and Index indices were studied, when signal-to-noise ratio is no more than 60 db this two damage detection indices showed excellent performance.