TABLE OF CONTENTS Vibration testing in structural dynamics work can be classified into three main groups.
First, in modal testing, the aim is to test a system or structure to obtain its vibration characteristics, from which its underlying equations of motion can be found. This identifies the system', leading to the alternate name of system identification. Before structural analysis had reached its present state of development, this was, in fact, the only way in which the equations of motion of complex structures, such as complete aircraft, could be determined with sufficient accuracy for, say, a flutter investigation to be made. At the present time, although it is possible to model virtually any structure by mathematical analysis alone, significant errors are still encountered, and a comparison between the predicted and the actual properties remains essential in critical cases. Therefore, current practice, particularly in aerospace, is to vibration test the structure as soon as at least one specimen is reasonably complete, in a ground vibration test, GVT, and compare the results with predictions. In the event of significant differences, the mathematical model must be changed.
The second group is environmental vibration testing. Here, the aim is to demonstrate that an item of equipment, typically electronic equipment installed in or on a vehicle, is capable of withstanding its vibration environment for the duration of its service life. The vendor of such equipment usually has to demonstrate this to the purchaser, by subjecting at least one specimen to the equivalent of the actual...
