A Conceptual Structural Health Monitoring System based on Vibration and Wave Propagation

Development of efficient methodologies to determine the presence, location, and severity of hidden damage in critical structural components is an important task in the design and construction of structural health monitoring systems in aging as well as new structures. In this article, a methodology for automatic damage identification and localization is presented. The structure is assumed to be instrumented with an array of actuators and sensors to excite and record its dynamic response, including vibration and wave propagation effects. In the vibrational approach, the data consist of the modal response of the structure produced by the actuators while in the wave propagation approach, they are the broadband signals due to ultrasonic waves propagating in the structures. Both types of signals are affected by the presence of defects. The approximate location and severity of an unknown defect is determined using a damage correlation index calculated from the frequency response function (FRF) of the structure. The damage index is a relative measure whose value depends on the differences in the dynamical properties of the undamaged (baseline) and damaged structures. The method is applied to simple structural components involving aluminum beams and plates with reduced local stiffness and a composite plate with impact damage. The potential application of the technique to practical health monitoring problems is discussed.