INTRODUCTION

Experimental modal analysis is the process of determining the modal parameters (natural frequencies, damping factors, modal vectors, and modal scaling) of a linear, time-invariant system. The modal parameters are often determined by analytical means, such as finite element analysis. One common reason for experimental modal analysis is the verification or correction of the results of the analytical approach. Often, an analytical model does not exist, and the modal parameters determined experimentally serve as the model for future evaluations, such as structural modifications. Predominantly, experimental modal analysis is used to explain a dynamics problem (vibration or acoustic) whose solution is not obvious from intuition, analytical models, or previous experience.

The process of determining modal parameters from experimental data involves several phases. The success of the experimental modal analysis process depends upon having very specific goals for the test situation. Every phase of the process is affected by the goals which are established, particularly with respect to the errors associated with that phase. One possible delineation of these phases is as follows:

Modal analysis theory refers to that portion of classical vibration theory that explains the existence of natural frequencies, damping factors, and mode shapes for linear systems. This theory includes both lumped-parameter, or discrete, models and continuous models. This theory also includes real normal modes as well as complex modes of vibration as possible solutions for the modal parameters. ^[1], ^[2], ^[3]

Experimental modal analysis methods involve the theoretical relationship...