A study of acoustic emission in piezoelectric multilayer ceramic actuator

Acoustic emission (AE) in multilayer ceramic actuators (MCA) has been studied. It was observed that AE signals could be concealed by sample's mechanical vibrations under usual MCA driving conditions. These vibrations were caused by an electrical coupling between the sample's piezoelectricity and the power supply's feedback. The AE was observed around the coercive field under bipolar driving. On the contrary, with unipolar driving, the AE was not present until the applied voltage reached a certain critical voltage. It was clarified that the AE generation in MCAs was strongly dependent on the maximum pre-applied stress (Kaiser effect), which corresponds to the applied voltage. The onset voltage of AE can be used to estimate the existing damages in the MCA. During the poling process, larger numbers of AE was observed in damaged MCA than that of un-damaged ones.