And yet another method for the identification of modal constants in experimental modal analysis.

Abstract

Modal Identification from Frequency Response Functions (FRFs) is a chapter of Experimental Modal Analysis (EMA) that many would consider being closed in a book and covered in dust. Yet, in a previous paper from the same authors, a new approach to determine the modal damping factors from FRFs was proposed. Contrary to other modal identification methods which are based on the dynamic motion governing equations, the method used as a starting point the dissipated energy per cycle of vibration. For lightly damped systems with conveniently spaced modes, it produced quite accurate results, especially when compared to the method of the inverse. The method used a plot of the sine of the phase of the receptance against its amplitude, whereby damping was determined from the slope. In this paper, it will be shown that this plot has other special properties, whereby the real and imaginary parts of the modal constants can be determined from the plot through numerical extrapolation.