Studies show that a rectangular plate is a useful modal structure that can be used for several purposes, such as comparing various modal systems and modal extraction algorithms, comparing test techniques, and training new personnel in these tasks. Plates roughly 53 cm x 32 cm x 2 cm (21 in. x 13 in. x 0.8 in.) were constructed by several participants from polymethyl methacrylate. The plates were then tested by the participants and the results compared with a NASTRAN analysis. The results show about 25 useful modes in the plate between 160 and 2500 Hz. The plate has a variable modal distribution with widely separated modes easily identified to very closely coupled modes quite difficult to separate. With careful experiments, the modal frequencies of the plate can be reproduced within 2 percent of the predicted values, and the mode shapes can be reproduced with errors of 20 percent or less. Less careful experiments can lead to large errors in frequencies, mode shapes, missed modes, and mixed modes.

This content is only available as a PDF.
You do not currently have access to this content.