Antech’s team will develop a concept for a Phased Array Modal Acoustic Emission (PA-MAE) passive monitoring system for large complex structures that provides at least a tenfold increase in sensor sensitivity thereby greatly improving the efficiency, precision, and reliability of the system. Our PA-MAE concept promises a revolutionary assessment capability that operates in real time to detect, locate, and evaluate major structural impacts and age related defects in all materials much more effectively than current health monitoring capabilities. Our proposal is founded on the same technology NASA used on the Space Shuttles after the Columbia incident to detect impacts during launch.
The gain in sensor sensitivity is achieved by stacking broadband piezoelectric crystal elements into a single sensor housing and then creating a phased array of the stacked elements at a single monitoring site. Stacking the sensors will increase signal amplitudes by summing outputs at the same detection location, while using a phased array and summing signals from closely spaced stacks will increase signal amplitudes via the phasing. Using both the stacks and the phased signals provides a 30 to 40 dB gain in sensitivity with no electronic gain required, thus significantly reducing electronic noise levels. In addition, the system will utilize a 24 bit analog-to-digital converter instead of the normal 16 bit converter to provide a larger dynamic range. This will eliminate the signal saturation due to extraneous noise signals that saturates current hardware leading to signal distortion and missed defect growth signals.
This novel approach results in a sensor array that is based on proven technology, monitors the full frequency spectrum of guided waves propagating as a result of damaging events, and detects and locates damage and cracks over very large areas of NASA structures more accurately, efficiently, and reliably than current monitoring systems.
Antech envisions the proposed enhanced PA-MAE monitoring system being used primarily as a Structural Health Monitoring system for NASA spacecraft and launch vehicles both manned and unmanned to detect/locate/characterize impact damage and age related defects, such as cracks in metallic structures and microcracks, fiber buckling, and fiber breakage in composite materials. With better sensor sensitivity, the system will be efficient, effective, and reliable, and provide real time mission critical information on the status of NASA structures.
The PA-MAE system could be used on Navy, Coast Guard, and commercial ships as a Structural Health Monitoring system able to monitor the entire hull for cracks and impacts with widely dispersed phased arrays. It could also monitor composite pressure vessels used for transportation of compressed natural gas and hydrogen fuels, above ground storage tanks for leaks, and concrete structures for damage.