Methods of Monitoring Longitudinal Stresses in Rails Using Acoustoelastic Effect

Abstract

Two methods of monitoring longitudinal mechanical stresses in rails by ultrasonic scanning using the acoustoelastic effect have been developed. According to the first method, stresses in a rail are monitored through temporal parameters of ultrasonic waves measured in an unloaded rail piece and in a loaded rail of a continuous welded rail track. This is done using two 18° angle beam piezoelectric transducers arranged in a pitch-catch configuration of rail scanning. This way, longitudinal and transverse waves are both excited simultaneously in the rail. Transducer acoustic axes lie in the same plane and face each other over the rail length. Upon reaching the back surface of the rail base, ultrasonic waves reflect from it and transform. The temporal parameters obtained from the reflected longitudinal and transverse waves as well as the waves transformed as a result of reflecting from the rail back surface were used to determine the longitudinal stresses. It was found that the measurement errors for the longitudinal mechanical stresses in the first method of monitoring is 2…6% on average. The second method for monitoring longitudinal stresses determines mechanical stresses more accurately as its measurement results are less influenced by rail height. The acoustoelastic coefficient of the transformed waves, kLT, has been determined experimentally. The methods of monitoring longitudinal stresses in rails by ultrasonic scanning using the acoustoelastic effect have been verified by measurements with a multichannel microprocessor strain-gauge system MMTS-64.01.