Ph.D. Proposal Presentation by Brad M. Beadle
Friday, May 18, 2001

(Dr. Jacek Jarzynski, advisor)

"Fiber Optic Sensor for Ultrasound"

Abstract

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.