Numerical-experimental study of contact-impact forces in the vicinity of a rail breakage

Abstract Broken rails or welds are among the rail discontinuities that generate significant impact forces in the wheel-rail contact surface. These forces lead to contact loss and thus an increase in the derailment probability. In this paper, experimental and analytical data are employed to study the impact force as the wheel crosses over a broken rail. In the experimental tests, the wheel-rail impact forces were measured using a Wheatstone bridge circuit. Prior to the field tests, the calibration factor of the Wheatstone bridge was determined by lab experiments. A three-dimensional finite element model (3D FEM) of the wheel and rail was developed and verified using the experimental test results. Using the numerical model, the effects of the distance between the breakage location and the adjacent sleeper, temporary repair of broken rails, and sleeper spacing on the wheel-rail impact forces were studied. The developed numerical model provided acceptable estimations of wheel-rail impact loads, as the difference of estimated and measured impact load is limited to 17%. According to the results of the numerical model, if the rail breakage is positioned between the two adjacent sleepers, impact forces are almost half of that of when the rail breakage occurs close to a sleeper. Moreover, the wheel-rail contact is not lost for any crossing speed of the vehicle. Also, by increasing the sleeper spacing from 60 cm to 70 cm, the impact load increases by an average of 20%, while reducing the sleeper spacing from 60 cm to 50 cm can decrease the impact loads by an average of 13%.