This report documents the development of a non-destructive system for inspecting the internal condition of concrete crossties using sonic/ultrasonic impact velocity and echo measurements. The system is a significant improvement over traditional, visual inspection techniques because it objectively quantifies the internal tie condition. The work was completed in two phases. Phase 1 was the initial development and proof of concept testing period, and Phase 2 developed automated prototype and completed field validation tests. Destructive testing of concrete ties reveals that this new system can accurately differentiate between undamaged and damaged ties with sufficient resolution to grade ties into five classes (1= no damage and 5 = severely damaged) based on the wave velocity through the crosstie. This grading scheme has been shown to closely match similar grading schemes used by railroads. NDT developed an on-rail carriage equipped with a solenoid impactor energy source, microphone sensors and a computer data collection and analysis system. Software was developed for data acquisition and real time data analysis and tie marking is included. Field tests in both yard and revenue service track locations have demonstrated the accuracy and repeatability of the system. This system can also be modified to be pushed, towed or suspended by a high rail vehicle. System improvements are planned to permit testing at speeds up to 20 miles per hour.
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