PZT Experimental Detection of Natural Frequencies for Compressed Thin-Walled Beams

By means of PZT pickups, we experimentally measured the natural frequencies of an aluminum thin-walled open profile under centered compression, and investigated the effects of end warping constraints on free vibration and buckling loads. The specimen was mounted on a MTS testing machine, controlling the axial displacement imposed to a beam end by the hydraulic jack. The free vibration frequencies were detected for different values of the compressive force. The experimental results are compared to those provided by an in-house numerical code, which investigates the elastic stability of thin-walled beams in a dynamic setting. Indeed, the code is able to follow the paths of natural frequencies versus the applied load, accounting for the effect of cross-sectional warping on both natural frequencies and buckling loads. The experimental results show that piezoelectric pickups, like the disk adopted, can be efficiently used for the experimental modal analysis of engineering structures.