Ultrasonics keep trains on the rails

US researchers claim to have identified an improved way of finding defects in steel railway tracks. A team led by Francesco Lanza di Scalea – professor of structural engineering at the University of California, San Diego – has used laser beam pulses to gently ‘tap’ on steel rails. A prototype vehicle rolls down the track delivering ultrasonic laser beam taps at one-foot intervals. Microphones are positioned a few inches above the rail and 12 inches from the downward-pointed laser beam. They detect any reductions in the strength of the ultrasonic signals, which indicates surface cuts, internal cracks and other defects. A prototype vehicle equipped with the UCSD technology detected at least 77% of internal defects and at least 61% of surface cuts in a recent test run. According to the Federal Railroad Administration, track defects account for about one-third of the 2,200 annual train derailments in the U.S. The UCSD team claims that its method is an improvement on existing methods because it sends the ultrasonic pulse along the rail, rather than firing it from above. “Our pulsed-laser technique is potentially very effective at finding internal rail defects,” said Lanza di Scalea.