EFFECT OF PIEZOELECTRIC CRYSTAL USED AS A VIBRATION DAMPER

Abstract

Piezoelectric crystals are used as vibration damper in smart structural system. In this experimental work total six numbers of piezoelectric crystals of different thickness were used as vibration damper and their damping effectiveness is observed. From all the testing models it has been noticed that this crystal can provide additional damping to the structure to which crystal is attached. Both free and forced vibration tests were performed with & without the crystal. Models which are used for testing are all MS beam: vertical cantilever, horizontal simply supported and horizontal fixed ends. All beams were of cross section 50 mm x 5 mm and cantilever was 1 m long, whereas fixed end and simply supported beams were of 1.67 m and 1.715 m length respectively. Cantilever on which forced vibration test were performed was 600 mm long and cross section was 50 mm x 10 mm. During the testing on each model i) the resistance in the shunt circuit, ii) crystal thickness and iii) number of crystal were the main variables. Upon keeping any two variables constant and by varying the rest one, response of the structure was recorded and analyzed later. During experiment it was observed that damping has been increased by 1.5 times to 3 times depending upon different models. A clear trend of increase in damping was observed against the decreasing resistance, against the increasing crystal thickness and also against the increased number of crystals attached. From results of the free and forced vibration test it is concluded that by the attachment of the piezoelectric crystal on the structure and by making a required electric shunt circuit the damping can certainly be increased by considerable amount. The energy dissipated in the free vibration test with crystal was higher than that of without crystal and this is a clear justification for the crystal in providing additional damping. Overall, it can be said that, the piezoelectric crystal can effectively be used to increase damping by using proper parameters related to its role of action when optimized economically. Hence, they can be good alternative to conventional dampers on the basis of their performance of operation & maintenance since it has minimal operating observation. Furthermore, for costly equipments as well as for many sensitive structures of smaller size, this crystal may be very useful since these equipments require undisturbing external condition than economization in procuring the crystal.