CAPE CANAVERAL, FL--NASA researchers have developed an ultrasonic gauge to measure preload in bolted joints.

Reliable, accurate bolt tension measurements are essential for critical bolts and studs located in ground support equipment and flight hardware. Existing commercial gauges perform adequately in most cases, but can produce unacceptable errors and uncertainties when measuring some configurations in flight hardware.

The ultrasonic bolt gauge, which was invented by Stuart M. Gleman and Geoffrey K. Rowe at the Kennedy Space Center, solves this problem. The gauge transmits ultrasonic signals through the bolt, generating echo waveform output signals. The gauge then uses cross-correlation and feature recognition analysis techniques to indicate bolt tension.