1. SUMMARY

In continuously welded rails high compressive and tensile forces can be created due to thermal expansion of the rail material Compressive force together with dynamic loads applied to the track by train can lead to dangerous track buckling.

Theoretical prediction of thermal stress, based on the measurement of rail temperature, are difficult due to numerous, usually unknown factors describing track structure and its displacements. Various nondestructive methods of stress evaluation were tested in laboratory and field conditions but none of them found practical application..

Paper describes ultrasonic monitoring of longitudinal forces in continuously welded rail. Presented are laboratory and field tests performed with shear waves propagated in the rail height direction and with longitudinal, subsurface waves propagated along the rail.