Residual stresses generated by repeated local heating events – Modelling of possible mechanisms for crack initiation
Artikel i vetenskaplig tidskrift, 2016

The hypothesis of thermal damage mechanisms by short-term local friction heating of rail or wheel steels leading to initiation of cracks, specifically squats (in some works called studs) in rails and crack clusters in wheels has given the inspiration for this study. A Finite Element (FE) model incorporating phase transformation from near pearlitic steel to austenite, and then to martensite was developed to examine developing strength and stress fields. Thermal strains on heating, cooling and phase transformations are naturally included, and the FE model also incorporates shrinkage due to tempering of the martensite during subsequent heat pulses. The material behaviour implemented in the model has been rationalised from experiments done on near pearlitic wheel steels, however the qualitative results are deemed applicable also for local thermal damage on pearlitic rail steels. The material is currently modelled as isotropic, with properties varying with phase, temperature and tempering state. The main contributions of this work is the modelling framework developed, specifically the careful modelling of martensite tempering combined with phase transformation. Different thermal sequences are examined to demonstrate the model´s capability. The computed strength and stress fields are used to discuss possible mechanisms of crack initiation.

RCF crack cluster

Finite element model

residual stress

phase transformation

stud

squat

thermal damage

Författare

Johan Ahlström

Chalmers, Material- och tillverkningsteknik, Materialteknologi

Wear

0043-1648 (ISSN)

Vol. 366 SI 180-187

Drivkrafter

Hållbar utveckling

Styrkeområden

Transport

Materialvetenskap

Fundament

Grundläggande vetenskaper

Ämneskategorier

Annan materialteknik

DOI

10.1016/j.wear.2016.05.029