An Experimental Investigation of the Parametric Resonance in a Buckled Beam

The principal parametric resonance of the second mode of a simply supported buckled beam is experimentally investigated. The simultaneous presence of prestress - compressive load - and initial curvature in the post-buckling range makes this system an interesting prototypical structural system with quadratic and cubic nonlinearities. Using three different experimental setups, frequency-response curves have been obtained for different excitation amplitudes. Moreover, the space-time characteristics of the nonlinear parametric-resonance motions have been measured and discussed. In particular, using a high-speed videocamera, interesting features of the motions have been found. There is a clear evidence of a zero-to-one internal resonance between the first (low-frequency) and second (high-frequency) mode.