Fatigue behavior of railway wheel steels in the very high cycle regime

The fatigue behavior of railway wheel steels has been investigated in the very high cycle regime under stress control at a frequency of 200 Hz on servohydraulic and resonance testing systems. Specimens machined from the rim of original wheels for high-speed passenger traffic exhibit a distinct change in the slope of the S-N curve at about 2.10(6) cycles. High-precision temperature and electrical resistance measurements are directly influenced by deformation-induced changes of the microstructure and allow to characterize the actual fatigue state in detail. Crack initiation was observed at specimen surface as well as inside the specimens. The physically based fatigue life calculation method "PHYBAL" on the basis of generalized Morrow, Coffin-Manson and Basquin equations leads to enormous benefits from the scientific and economic point of view. S-N curves calculated with temperature and resistance data measured after 10(4) cycles, i.e. after only 50 seconds in a test at 200 Hz, matches very well with the conventionally determined one.