Reliability assurance of railroad wheels by ultrasonic stress analysis

Braking using brake-shoes causes tensile circumferential stresses in the rim of railroad wheels and sometimes a growing of a heat crack till the failure of the wheel. In order to assure the reliability of the wheels and the safety of the traffic, the stress states in the rims have to be inspected periodically. Ultrasonic techniques have been optimized for that purpose. Using linearly polarized shear wave, the difference of the principal stresses acting in the circumferential and along the radial directions are evaluated as function of the distance from the rolling surface. Based on the IzfP prototype system for the automated ultrasonic time-of-flight measurement and evaluation of stress states, a system has been built and optimized for the automated data acquisition and evaluation of the profiles of the principal stress difference in rims of monoblock railroad wheels.