Investigation of the effect of constructional parameters of discrete attachments on energy transfer from a vibration source

Due to the destructive effects inherent in vibration, it is generally undesirable in systems, structures and machine components. This unwanted effect also carries with it the loss of a certain amount of energy. The question of whether this lost, useless energy can be collected and reused has motivated many researchers. Attachments composed of mass and spring elements were placed on the main structure in varying numbers and positions, symmetrically along both the x and y axes of the plate. These attachments were considered as energy harvesters to be used in power-consuming electronic devices. The finite element method was used to investigate the coupled behavior of multiple elements. The natural frequencies of the discrete attachments were tuned to be identical with the first mode of the bare plate. It has been ensured that the total weight of the attachment masses remains less than one-tenth of the main structure's weight. The mass of the springs used in the attachments has not been taken into account. To determine the kinetic energy (mass) and potential energy (spring) transferred from the plate to the attachments, the plate has been harmonically excited at its center in the first and second free vibration modes. As observed from the results, the highest energy has been obtained when the harmonic excitation is applied in the first mode of the plate, provided that the attachment parameters are adjusted to match the natural frequencies of the attachments with the first natural frequency of the plate. It was found that while the total harvested energy increased with the number of attachments, the energy per attachment decreased. Since all four edges of the plate are fixed (restricting any movement), an increase in energy has been observed when the attachments are placed closer to the center of the plate. When the coupled frequencies of the bare plate and attachments were varied – first by keeping the mass constant and by changing the spring stiffness, and then by keeping the stiffness constant and changing the mass¬ – it was determined that the highest energy was obtained when the frequency ratio was equal to 1.