Residual Stresses in Martensite after Multiple Heating Events

The technical problem studied concerns repeated friction heating in a railway wheel-rail contact surface. The temperature is high enough to cause austenite formation in a thin layer, and thereafter rapid self-cooling yielding martensite. Volume expansion occurs during transformation to martensite. On repeated heating, martensite is tempered and the corresponding shrinkage occurs. This causes tensile residual stresses in the brittle material and in combination with the high contact stresses this can lead to initiation of cracks. The FE modelling includes phase transformation, and phase dependent material properties like thermal expansion and flow stress. The experiments for the basis of this study and a calculation example are partly reported in the following reference:

Cvetkovski, Krste; Ahlström, Johan; Karlsson, Birger: Influence of short heat pulses on properties of martensite in medium carbon steels. Materials Science and Engineering: A, 561 pp. 321-328. (2013)