For the last several years, the FEM (Finite Element Methods) modal analysis has become an indispensable means of predicting modal characteristics of mechanical structures, i.e. natural frequencies and the corresponding modes. However, it is also well known to practioners that the analysis model has to be validated by experimental testing for its assuredness. In this paper, a practical approach using time-average holographic interferometry to validate the FEM modal analysis is proposed. Following this approach, a graphical comparison between the holographically-measured mode shapes and the corresponding FEM-generated ones is displayed side by side. Further more, the numerical calculation of the Modal Assurance Criterion (MAC) is presented. The smoothing cubic spline fitting is employed for acquiring data from holographic fringe patterns. It is demonstrated that with this technique the numerical calculation of MAC is straight forward and relatively easier than other existing techniques.
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