Materials and Structures

Structural Health Monitoring Laboratory
V. S. Rao and A. C. Okafor

This laboratory supports research in the areas of damage detection and nondestructive testing in various engineering materials and structures. It has extensive facilities to cover all areas of this research and comprise of the following equipment:

1. Acoustic Emission system
2. Ultrasonic C-Scan system
3. Fiber Optics system
4. Laser Shearography
5. Scanning Laser Vibrometer
6. Infrared Thermography
7. Eddy current system

These facilities are located partly in the Laboratory for Industrial Automation and Flexible Manufacturing in the Department of Mechanical and Aerospace Engineering and partly at the Intelligent Systems Center. High performance Sun Ultra and Windows NT workstations with unrestricted access are also available at the disposal of the graduate research assistants. Bridgeport Milling machine, Okuma CNC lathe and the Cincinnati Milacron Sabre 750 4-axis vertical machining center are also available for in-house fabrication of damages in structures. The Okuma CNC lathe also has embedded acoustic emission sensors for research in the areas of machine tool health monitoring and diagnostics.

The current research project in this laboratory involves detection and assessment of damage in advanced aerospace materials and mechanical and civil structures, supported by the National Science Foundation. The research projects are highly interdisciplinary in nature and require implementation of concepts in mechanical design, finite element analysis, vibrations, manufacturing, digital signal processing, digital image processing, data acquisition systems, control systems and extensive knowledge of sensors and statistical methods.

The objectives of the research are to 1) Detect the presence of damage (surface, subsurface and hidden) in a structure; 2) Determine the location of the damage in the structure ; 3) Quantify the damage within the structure; 4) Implement an intelligent decision making algorithm to classify and predict the damage in terms of severity to the life and performance of the structure; 5) Investigate multi-sensor damage detection methods and neural data fusion to increase the accuracy of damage classification and reduce false alarms.

Research in the areas of Acoustic Emission, Ultrasonics and Vibration based damage detection methods are currently under investigation for damage detection in advanced composites, aluminum alloys and concrete structures. The Scanning Laser Vibrometer with advanced signal processing techniques like wavelet transforms have been used for damage detection in aluminum alloys. Finite element analysis methods are employed to correlate theoretical and experimental results. The ultrasonic C-Scan method is being used extensively for detection of small holes and voids in aluminum and concrete, and for assessing low impact damage and delaminations in composites. Laser Sheraography and Thermography is also being investigated independently to validate C-Scan results and explore the possibility of neural data fusion for enhanced detection and prediction of damages.