Technical Reports

Railroad Rail Flaw Detection System Based on Electromagnetic Acoustic Transducers

  • 01
  • Sep
  • 1988
AUTHOR: George A. Alers
SUBJECT: Tracks & Structures
KEYWORDS: EMAT, ultrasonic inspection
ABSTRACT: This report describes the design, construction and preliminary testing of an ultrasonic inspection vehicle intended for the detection of flaws in railroad tracks that are in commercial service. It differs from existing inspection systems in that it employs an ultrasonic transducer that does not require any kind of coupling liquid between the sensor head and the rail. Thus, the operation of the system is simplified, lubricated rails are inspected without special cleaning processes and there is a potential for higher speed scanning of the rails. In addition, the couplant-free transducers are able to utilize special ultrasonic wave types that increase the probability of detection of certain transverse defects in the head of the rail and vertical split head defects in the web. A computer has been incorporated into the data processing channel to allow recording of all the ultrasonic signals as well as for presenting the operator with deflections on a strip chart recorder that both act as alarm indications as well as provide information on the characteristics of the flaw. By permanently recording each ultrasonic response, the data can be reanalyzed at different sensitivity settings at a later time so that more detailed examinations of the track can be carried out off-line without interference with the normal use of the railroad.