Rail Bars Evaluation

Laser-ultrasound diagnostics based on structurometric analysis does not have world analogues and is one of the effective tools for preventing emergency situations associated with the ejection and catastrophic fracture of rails (Russian patent #2381496 from 2008.05.29, US patent 8,368,289 from 2013.05.02, Ruassian State Service of Standard Reference Data Methods МЭ 215-2013). The technique provides high accuracy of measurements of sound velocity by time-of-flight method (± 1% with a spread of 0.05%), the possibility of detecting small defects (~ 300 μm) and the practical absence of a dead band.

The measurement of the stressed state of the rail is based on the acoustic-elastic effect - the dependence of the velocity of elastic waves in the material on its stress state. Theoretical analysis gives a linear dependence of the elastic wave velocities on the effective stress values. The greatest sensitivity has longitudinal waves propagating along the direction of the acting stresses. Practical measurements of stresses in the welded seams of rails were carried out on the RSP-17, and on the tracks - in the Gorky branch of the Russian Railways. A head ultrasonic wave was used to control the stressed state of the rail which was excited and detected by a laser-ultrasonic transducer with pitch-catch configuration PLU-6N-02.
 

 

The rail bars controled in a strained and released condition (in the non-stressed state of the rail). The obtained dependences characterize the distribution of the velocity of the head wave in the material of the rail itself. Differences in the behavior of the velocity of the head wave at the ends of the control section determine the zones of influence of the tension system and the fixed section of the rail.