Energy dissipation through joints: theory and experiments

A new qualitative non-destructive evaluation (NDE) technique based on a modification of the high-frequency impedance measured with an integrated piezoceramic (PZT) actuator-sensor has been successfully demonstrated at the Center for Intelligent Material Systems and Structures. An important characteristic of this NDE technique is the localization of the PZT's sensing area due to energy dissipation. For a better understanding of this phenomena, this paper will present an analytical method to determine the energy dissipated through joints at high frequency and its relation to the localized actuation-sensing region. The structure used for this analysis consists of two beams 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 beam theory is used to model the structure. Using the equations of motion, the dynamic stiffness matrix is assembled in the frequency domain. Then, the energy dissipated in the joint is modeled linearly using mass-spring-dash pot systems and nonlinearly with the application of nonconservative friction clearance systems. This work is the first effort in the high-frequency modeling of structural joints: other work was only concerned with the modeling of the few first modes of vibration. Case studies and experimental verification will then follow. (C) 2000 Elsevier Science Ltd. All rights reserved.