Experimental Analysis of the Cyclic Deformation and Damage Behavior of Characteristic Wheel and Rail Steels

Abstract

As part of an extensive study exemplary results of the basic examinations which were carried out within this project, transmission electron microscopic (TEM) investigations of the microstructure of a cyclic loaded rail steel and the deformation and lifetime behavior of a cyclic loaded wheel steel are represented. For the TEM investigations specimens are worked out of the head of unused rails. With these specimens push-pull tests under several loading conditions are carried out. After failure foils are taken from the gauge length to perform TEM investigations to determine the appearing dislocation structure in the ferritic phase of the pearlite. Additionally the observed dislocation structures are compared with that one found nearby the surface of a used rail taken from a high speed track and that one found in unused rails in the as-received condition. To investigate the cyclic deformation and lifetime behavior of a wheel steel specimens were worked out from several layers of the rim of a monobloc wheel, grade R7, used in high speed trains. Due to the heat treatment at the end of the manufacturing process there are different microstructures within several regions of the wheel rim. The specimens represent these different microstructures. Stress controlled fatigue tests are performed with these specimens. The cyclic deformation behavior, the lifetime behavior and the endurance limit are deduced from push-pull tests. The influence of the different microstructures on the deformation and lifetime behavior is discussed.