(Dr. Jacek Jarzynski, advisor)
"Fiber Optic Sensor for Ultrasound"
In ultrasonic nondestructive testing and in acoustic emission measurements, there is a need for sensors which respond preferentially to the in-plane (tangential) component of surface displacement, as opposed to the out-of-plane (normal) component. Such a sensor would provide better discrimination against environmental noise since environmental noise produces, in many structures (plates, shells), mainly out-of-plane surface vibrations. The objective of this study is to develop an interferometric fiber optic sensor for measuring in-plane surface displacements at ultrasonic frequencies in the range 50-200 kHz.
Several fiber optic sensor designs have already been tested.
The most successful design to date consists of a large number of concentric
optical fiber wraps which have been laid flat and bonded to a thin aluminum
base. Experimental measurements of this “spiral-wrap” sensor’s response
and a quasi-static model of the sensor are presented. Future work
will involve developing a dynamic model of the spiral-wrap sensor, optimizing
the sensor, and comparing the in-plane and out-of-plane response of the
sensor to that of a piezoelectric sensor.