Abstract
The paper presents a method of identifying the global modal parameters of a mechanical structure from the free decay responses, which is based on the state variable method expressed in the form of a difference state equation. A recursive algorithm is proposed for calculation of the state transition matrix. The modal shapes of a large number of stations for each mode are obtained by making use of the data acquisition system with a few channels, which results from the uniformity of the normalized modal shapes. The generalized mathematical model of the method is related to the other time domain methods. As illustrative examples, the method is applied to the identification of global modal parameters of a free-free straight pipe and a "T"-shaped plate structure. The identified results are in good agreement with the analytical ones.
