Energy dissipation through joints: theory and experiments

A new qualitative non-destructive evaluation (NDE) technique based on a mod ification of the high-frequency impedance measured with an integrated piezo ceramic (PZT) actuator-sensor has been successfully demonstrated at the Cen ter for Intelligent Material Systems and Structures. An important character istic of this NDE technique is the localization of the PZT's sensing area d ue to energy dissipation. For a better understanding of this phenomena, thi s paper will present an analytical method to determine the energy dissipate d through joints at high frequency and its relation to the localized actuat ion-sensing region. The structure used for this analysis consists of two be ams connected with a bolted joint and each having free boundary conditions. Due to the high-frequency range employed, theoretical assessments are made using a wave propagation approach. For the same reason, the Timoshenko bea m theory is used to model the structure. Using the equations of motion, the dynamic stiffness matrix is assembled in the frequency domain. Then, the e nergy dissipated in the joint is modeled linearly using mass-spring-dash po t systems and nonlinearly with the application of nonconservative friction clearance systems. This work is the first effort in the high-frequency mode ling of structural joints: other work was only concerned with the modeling of the few first modes of vibration. Case studies and experimental verifica tion will then follow. (C) 2000 Elsevier Science Ltd. All rights reserved.