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Special issue on structural health monitoring: Wave propagation and interaction with damage in complex structures
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Dynamic behaviour of metallic and composite plates under in-plane loads
No full textThe dynamic behaviour of plates under compressive in-plane static loads will be examined in the present paper. From an analytical point of view the effects of forces acting in the undeformed middle surface of plates on the bending natural frequencies and mode shapes are well known. For a simple plate as the compressive edge force approaches to the buckling value the first natural frequency tends to zero. Nevertheless the experimental assessment is complex as the middle plane of the plate does not remain plane up to the critical compressive load, owing to the initial imperfections of the plate and misalignment of load. The dynamic behaviour, in fact, is strongly sensitive to the change of the middle plane curvature. Measured natural frequencies and, in same case, also mode shapes are quite different from the predicted theoretical values when curvatures become not negligible. In the paper is shown that anyway it is possible to predict with a good accuracy the buckling load. Using a limited number of measured natural frequencies at various compressive loads, the buckling load is achievable extrapolating these values. This procedure has been applied for an aluminum alloy plate for two edge constraint conditions. Tests on composite plates under compressive and shear load are going to be performed in order to assess the procedure for a more general case
A Vibration and Wave Propagation Based Methodology for Near Real- Time Damage Monitoring of Composite Structures
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Autonomous Health Monitoring of a Stiffened Composite Structure Using Statistical Damage Index Approach
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An Automated Damage Identification Technique Based on Vibration and Wave Propagation
No full textThis paper is concerned with the detection and characterization of hidden defects in advanced structures before they grow to a critical size. A novel method is developed using a combination of vibration and wave propagation data to determine the location and degree of damage in structural components requiring minimal operator intervention. The structural component is to be instrumented with an array of actuators and sensors to excite and record its dynamic response. A damage index, calculated from the measured dynamic response of the structure in a reference state (baseline) and the current state, is introduced as a determinant of structural damage. The index is a relative measure comparing the two states of the structure under the same ambient conditions. The indices are used to identify damages in the forms of delaminations and holes in composite plates for different arrangements of the source and the receivers. The potential applications of the approach in developing health monitoring systems in defects-critical structures are discussed
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