Ultrasonic in-situ determination of the regression rate of the melting interface in burning metal rods

Results of tests in which metallic rods are burned in oxygen enriched atmos pheres often include the determination of the regression rate of the meltin g interface for the burning test specimen. This regression rate is used as an indication of a metallic material's relative flammability and its genera l ability to sustain burning under the test conditions. This paper reports on the development and first application of an ultrasonic measurement syste m that enables in situ measurement of the regression rate of the melting in terface in burning metal rods. All other methods currently used for determi ning this parameter are based on posttest, visual interrogation, which is c ostly and often inaccurate. The transducer and associated equipment used to drive and record the transducer's output signal are described and typical results for iron rods burning in pure oxygen at different gauge pressures a re given along with a comparison of these results with regression gates obt ained from visual interrogation. The excellent sensitivity, accuracy and re liability of the new ultrasonic transducer are demonstrated, thus indicatin g the transducer's great potential. (C) 1999 Acoustical Society of America. [S0001-4966(99)00702-X].