Published online by Cambridge University Press: 04 July 2016
In the vibration of isotropic rectangular plates, the phenomenon of the simultaneous excitation of two separate modes having equal frequencies is well known. Wallerobserved complex nodal patterns on isotropic rectangular plates, and she stated that such combinations were possible because of the internal damping of the plates, which reduced the sharpness of resonance.
Warburton considered the existence of modes m/n±n/m for a clamped plate and showed that when a plate is square, for the mode 4/2 + 2/4, the nodal lines do not lie parallel to the edges of the plate. Furthermore, it was proved that for a square clamped plate, the modes m/n±n/m have discrete frequencies.