SBIR-STTR Award

The objective of this proposal is to demonstrate the feasibility of detecting damage in structures using Laser Doppler Vibrometry (LDV) and further lead to the development of a robust aerospace structural health monitoring system. The proposed concept is based on use of LDV to measure velocities and displacements associated with high frequency operational deflection shapes as well as lamb waves. Anomalies and changes in the measured displacement maps are then identified through intelligent data processing techniques that can be used to locate and characterize the extent of the associated damage. The underlying principle of the proposed damage detection methodology relies on the evaluation of changes in displacement amplitudes, curvatures and energy distributions associated with high frequency vibrations and wave propagation phenomena. The proposed research is supported by preliminary theoretical and experimental work which clearly demonstrates the effectiveness of the proposed techniques and the potential of their integration. The ideal scenario for the ultimate usage of the LDV based damage detection technique would be the injection of small amounts of energy into the structure and then determining the damage status of the structure in a brief time span. The proposed techniques will provide the necessary building blocks for such a scenario.

Keywords:
Structural Health Monitoring, Fatigue And Impact Damage, Disbond And Delamination, Laser Doppeler Vibrometer, Dynamics-Based Ndi

Phase I efforts have concluded in successful demonstration of the use of a Laser Doppler Vibrometer in detection of cracks in composite and metal test specimens. A Damage Index formulation based on the distributed strain energies associated with the dynamic response (low as well as high frequencies) has been shown to vividly indicate the presence, size, and orientation of a damage. Phase II efforts provide an opportunity for advancing the reasearch and maturing the technology for field demonstrations. A new concept of structural health monitoring , through embedded software, is being proposed. Theoretical formulations of damage detection using perturbation method, and elastic wave propagation provide a solid foundations for our technology. Hardware innovations are being pursued by designing Continuous Scanning Laser Doppler Vibrometer to replace the discrete systems of today.

Keywords:
Structural Health Monitoring, Damage Detection, Laser Doppler Vibrometer, Lamb Wave, Fatigue And Cor