Rolling (rail vehicle)
In rail vehicles , rolling is a damaging vibration condition of a wheelset that occurs when operating at the limit of static friction . As a sustained state, this is only possible with rigidly controlled drives, as operation is unstable at the static friction limit. This instability, see stick-slip effect , stimulates the torsional vibration of the two wheels against each other. The difference between static and sliding friction that is necessary for the excitation occurs more at medium and higher coefficients of friction.
The vibration frequency is given by the torsional stiffness of the shaft and the mass moment of inertia of the wheels and is usually between 50 and 100 Hz. Due to the rapid load change, material fatigue through to vibration fracture of the shaft must be considered as a hazard in the safety verification. Catastrophic failure by rolling has not yet become known, but failure of the frictional connection with pressed-on wheels is known.
The anti-roll protection is a function of the traction control to avoid this operating state by reducing the torque or changing the speed slightly (increase in traction, decrease in braking).