Computation of Wave Propagation in Damped Specimen for Damage Detection

Abstract

Aim of a structural health monitoring system must be to collect sufficient information about the damage for appropriate remedial measures to be taken to ensure safety. The preliminary step in the process of damage assessment is locating the damage .One of the challenges faced by the structural health monitoring system is monitoring in-flight damages. Localization of in-flight damages or sudden impacts can be achieved by monitoring the acoustic emissions in real time mode. In this paper, an approach based on the employment of Piezo-electric transducer rosettes to locate the acoustic emission source in an aluminum plate is presented. Using the strain gage rosette concepts adapted for piezoelectric transducers, the wave strain principal angles are determined. When two rosettes are used, the intersection of the principal wave strain directions detected by the rosettes gives the wave source location. The method does not require the knowledge of wave velocity in the medium in contrast to the time of flight based location. Hence, this technique can be used in anisotropic or complex structures where the source localization using the conventional time of flight method is difficult. The principal strain angle using the voltage response of the transducers and the rosette principles are obtained and the co-ordinates of the wave source location are calculated using the co-ordinates of the centroids of the rosettes in MATLAB.According to the tests, the rosette piezo-transducer outperforms the single piezo elements to a degree justifying its complexity. The rosette piezo transducer provides more damage related information compared to single elements and hence the performance of the damage detection system can be significantly improved if rosettes are used.

Piezoelectric Based Lamb Waves Generation and Propagation in Orthotropic CFRP Plates: II. Influence of Interfacial Stress Distribution

“…For the structures of shell, plate or beam-like shape the Lamb wave-based SHM systems are widespread due to that these waves are able to propagate over large distance interacting with different defects and ensuring their identification. The various aspects of using Lamb waves in the active SHM system are outlined and considered in the monograph [1], papers [2][3][4][5] and many others. The Lamb waves can be produced in a structure by a variety of different techniques including piezoelectric transducers made of monolithic ceramics in the forms of circular [6][7][8][9], annular tablets [10] or rectangular PZT patches [10,11]; by PZT wedge transducers [12,13], piezoelectric wafer active (PWAS) and macro-fiber composites (MFC) actuators [14][15][16][17], and by laser beam excitation [18]; while for sensoring of the waves, which are reflected or scattered on the defects, by the small piezoelectric transducers [5,19,20] or some non-contact techniques are most often used.…”

Piezoelectric Based Lamb Waves Generation and Propagation in Orthotropic CFRP Plates: I. Influence of Material Damping

“…beamsteering. These aspects of using Lamb waves in the active SHM system are outlined and considered in the monographs [1,2], in the papers [3][4][5][6] and others.…”