Measuring and testing – Vibration – By mechanical waves
Patent
1977-05-31
1978-10-24
Kreitman, Stephen A.
Measuring and testing
Vibration
By mechanical waves
73629, G01N 2900
Patent
active
041214676
ABSTRACT:
It is often desirable to measure absolute and relative USW velocities in a specimen. One example is a specimen which is to be tested for residual surface stresses. The specimen is provided with two scratches which are parallel and a known distance apart. An ultrasonic surface wave (USW) transducer is attached to the surface of the specimen in such a way as to efficiently transfer USW energy to the specimen. During testing, the incident pulse from the transducer is partially reflected at each scratch. The same transducer generates and detects both reflections. The transducer output goes through a clipping circuit which clips the large incident voltage spikes in the output and passes the smaller, echo voltages through to an oscilloscope. The oscilloscope horizontal sweep is driven at a frequency which is the reciprocal of the difference in arrival times between the two reflected pulses.
A dual pulse delay generator is detailed as a double strobe delay generator having a plurality (herein six) of integrated circuits (IC's ) interconnected as described below to provide the Z-axis input to the oscilloscope.
REFERENCES:
patent: 3812709 (1974-05-01), Benson et al.
patent: 3946256 (1976-03-01), Day et al.
patent: 4013983 (1977-03-01), Hartemann
patent: 4028648 (1977-06-01), Hartmann et al.
Papadakis, "New Compact Instrument for Pulse-Echo-Overlap Measurement of rasonic Wave Transit Times", Review of Scientific Instruments, 7-1976, pp. 806-813.
Hellier et al., "Pulse Echo Overlap for Measurement of Velocity of Sound", Journal of Physics E, pp. 352-354, 5-1975.
Sagnes et al., "Oscilloscope for Velocity Measurements of Acoustic Surface Waves," Electronics Letter, pp. 421-422, 8-1972.
Cook et al., "Surface Waves at Ultrasonic Frequencies," ASTM Bulletin, pp. 81-84, 5-1954.
Edelberg Nathan
Kreitman Stephen A.
Schmidt John F.
Taucher Peter A.
The United States of America as represented by the Secretary of
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