Ultrasonic characterization of stress states in rims of railroad wheels

Freight trains are braked by pressing brake-shoes on to the rolling surface of the wheels. Due to the heat, put in during the braking periods and the subsequent cooling, tensile stress states are developed in the rims of the wheels. Cracks in the rolling surface, which are not harmful otherwise may grow under the influence of the tensile stress and may even cause the failure of a wheel. In order to assure the reliability of the wheels and the safety of the traffic, the stress states of railroad wheels need to be inspected periodically.