Volume 3, Issue 1 (January 1975)
Signal Processing in Nondestructive Testing
Signal averaging has been used to improve the clarity of flaw indications in an electron beam weld. The delay of an electronic gate has been synchronized to the transducer motion to improve the detectability of a tight interface crack in a tensile specimen. Cross-correlation techniques and multiple transducer arrays have been used to improve the signal-to-noise ratio of artificial flaws in welded panels. Signal averaging has been used to reduce random noise in the through-transmission ultrasonic inspection of a honeycomb composite. Megacycle range ultrasonic flaw information has been recorded on a low frequency FM tape recorder by rapidly sweeping an electronic gate through the time interval of interest. A lock-in amplifier has been used to produce quantitative data in both single-coil and double-coil eddy current systems. Cross-correlation techniques and a multiple-coil eddy current probe have been used to reduce surface roughness noise in an eddy current crack detection system.