An energy harvesting and damage sensing solution based on postbuckling response of nonuniform cross-section beams

Postbuckling response of elastic beams has been widely used in many systems to develop efficient energy harvesting and damage sensing mechanisms under quasistatic excitations. In particular, the snap-through behavior of bilaterally constrained beams can be used to transform low-frequency and low-rate excitations into high-rate motions. Using a piezoelectric energy harvester, these motions are converted into electric power. However, the efficiency of buckling-based energy harvesters highly depends on the postbuckling behavior of the buckled elements. Inadequate control over the beam's response critically impedes the application of the mechanism. This study aims to control the location of the snap-throughs and the spacing between the transitions in order to increase the levels of the harvested energy and tune the sensitivity of the sensor. As uniform prismatic beams do not allow for such control, nonprismatic cross-section beams are herein investigated. An energy-based theoretical model is developed in this study to investigate the effect of different shapes and geometries on the postbuckling response of nonuniform beams. The total potential energy of the system is minimized under constraints that represent the physical confinement between the lateral boundaries. Experimental results prove that the theoretical model is accurate and can be used to optimize the buckling elements. Results show that the spacing between the transitions can be tuned. Furthermore, an optimal buckling element can improve the energy conversion efficiency by more than 290%.