VIBRATION CHARACTERISTICS OF A STEEL FRAME USING PIEZOELECTRIC CRYSTALS AS DAMPERS

Abstract

Piezoelectric crystals are used as vibration dampers in smart or intelligent structural systems. In the present experimental work, three types of piezoelectric crystals having different thickness were used for increasing the damping of a system and checking their effectiveness in reducing the amplitude of vibration. From all the results obtained with different combinations, it has been noticed that the piezoelectric crystals have the capacity to provide additional damping to the structure. Free and force vibration tests were performed with and without crystal, with three different variables namely, crystal thickness (0.5, 1.0, 1.5 mm) resistors (2.2, 10, 33, 67ohms) and positioning of the crystal (Bottom, Middle and Top position). Thus, totally making a total 36 cases with piezoelectric crystal and 1 case without crystal. , The structure was a steel space frame with beams and columns attached through welding. Columns and beams of this frame were built with MS plates having a section 63.5 mm width and 6 mm thick. The height of the frame being 500 mm. a steel plate of 10 mm thickness, used as slab was welded on all the four sides. During the analysis, two out of the three variables were kept constant and one is, varied and changes were observed. During the experiment it was observed that the damping has been increased by almost 1.2 times to 10 times depending upon different cases. A clear picture of increase in damping was seen, against the increasing crystal thickness and against the decreasing resistance. As the position varied from BOTTOM to TOP, there was a decrease in the damping, thus making the positioning of the crystal also a very important factor of design. It was seen that, maximum damping was seen in BOTTOM position and less in TOP position. The change in energy dissipation was observed to be 1.5 times to 14 times depending on the case, considered. From the results obtained from the free vibration as well as force vibration, it is concluded that, by the use of piezoelectric crystals, damping of the system has been drastically increased and energy dissipation capacity of the structure was also increased considerably.