Application of Ultrasonic Phased Arrays for Rail Flaw Inspection

The average number of Federal Railroad Administration’s (FRA) reportable broken rail-related derailments between 1995 and 2005 was approximately 28 annually. The annual property damage resulting from the accidents was approximately $35 million Programs cosponsored by FRA and the Association of American Railroads are directed at determining causes of internal rail flaws and identifying applicable nondestructive testing (NDT) technologies that can detect the flaws. Through continued efforts from the joint research program, the development and implementation of improved rail metallurgies and maintenance programs are expected to decrease rail flaws. In addition, through increased reliability of flaw detection technologies, a decrease in rail failures and accidents is expected. The research programs also continue the identification, evaluation, and development of emerging NDT technologies applicable to increased rail flaw detection reliability. Technologies investigated to date include laser-generated ultrasound, low-frequency eddy current, guided ultrasonic waves using magnetostrictive sensors, and ultrasonic phased arrays. Scanning capabilities for phased-array technologies do not currently accommodate real-time dynamic rail inspection at speeds greater than 5 mph. But the method has demonstrated its feasibility for Web, base, and head inspection focused on flaw sizing and characterization. This report provides the results of research sponsored by FRA, through the Transportation Technology Center, Inc., regarding the application of phased-array ultrasonic technology to inspect rail for service induced transverse defects in the head of the rail.