Thomas M. Proctor
T-PROsic, 22901 Old Hundred Rd., Barnesville, MD 20838
Speed of sound in solids has been measured by a number of different techniques over the past 5 decades. Unfortunately, consistent repeatability and accuracy have been a rare occurrence. Many error-producing problems of a fundamental nature have kept this experimental finding suspect at best. In liquids, the definition, dl/dt, for speed of sound can be used to check the accuracy of the method but, for solids, such incremental changes in path length are not possible. In the case of a plate, a combination of modifications to the procedure for the normal on-axis-plane wave experiment are possible. Over the past 15 years, a number of improvements and innovations have enhanced the field of acoustic emission. The development of a point contact receiving transducer and a repetitive impulsive point source in conjunction with developed Green's function theory for the plate geometry have allowed for a new way of doing the ultrasonic velocity measurement. This new approach will be discussed and error problems inherent in this technique will be examined. Results of change in length versus change in time of flight will be analyzed. [Work performed by contract to NIST.]