Crack Sizing Using EMAT/Laser System

The purpose of this program is to develop a hybrid ultrasonic system using laser generated ultrasound and EMAT detection for sizing cracks in steasdel. This technique has direct application in detection of cracks in steel pressure vessels without shutting down the plant. Initial testing on 1" aluminum plates with artificial cracks has shown that laser generation using a single line source and detection with a 1" X 1" meaner line EMAT coil works well for detection of the crack. However, interference of various waves from mode conversion at the crack tip and back surfaces does not allow sizing of the crack. Current efforts are being directed towards designing a more appropriate system which eliminates the interfering wave arrivals. Such a system may include two line sources and a single detector, or two detectors with a single source. After successful completion of the system design, steel plates will be tested.

In addition to the experimental work, a model for ultrasonic crack diffraction is being developed which will take into consideration the source characteristics.

Experimental Setup: 2 Cylinderical lenses for line source generation and EMAT (gold) for detection

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