stage 6 triennial report 1 July 2009–30 June 2012 ... - CHARMEC

Materials and maintenance – Material och underhåll (MU) – Werkstoff und Unterhalt – Matériaux et entretien
MU3. MARTENSITE FORMATION AND DAMAGE AROUND
RAILWAY WhEEL FLATS
Martensitbildning och skadeutveckling kring hjulplattor
Martensitbildung und Beschädigung an Flachstellen
Formation de martensite et dommage autour des plats de roue
The mu3 project was completed with Johan Jergéus’
successful defence in public of his doctoral dissertation
in January 1998, after which he left Chalmers. The title of
his dissertation is “Railway wheel flats – martensite formation,
residual stresses, and crack propagation”. The facultyappointed
external examiner of the dissertation was
Professor Lennart Karlsson from the Department of
Computer Aided Design at Luleå Technical University,
Sweden. Professor Roger Lundén together with Professor
Bengt Åkesson from Chalmers Solid Mechanics (now Applied
Mechanics) supervised the research in project mu3.
A numerical model for the prediction of martensite
formation under and around a wheel flat was developed.
The model was calibrated against the approximately 240
wheel flats that were created under controlled conditions
in the field trials at Silinge (near Flen west of Stockholm)
in September 1996. A constitutive model was developed
Prediktering av livslängd hos järnvägshjul
Vorhersage der Lebensdauer von Eisenbahnrädern
Prédiction de la durée de vie des roues ferroviaires
The mu4 project was completed with Anders Ekberg’s
successful defence in public of his doctoral dissertation in
April 2000 and his finalizing work up to June 2000. The
title of the dissertation is “Rolling contact fatigue of
railway wheels – towards tread life prediction through
numerical modelling considering material imperfections,
probabilistic loading and operational data”. The facultyappointed
external examiner of the dissertation was Professor
Michael W Brown from the Department of Mechanical
Engineering at the University of Sheffield, uk. Professor
Roger Lundén of Chalmers Solid Mechanics (now
Applied Mechanics) supervised Anders Ekberg’s research.
An important outcome of the mu4 project was the computer
program wlife (Wheel Life) for estimation of the
fatigue life of the rim of forged wheels in operation. wlife
is based on the results of numerical simulations and laboratory
and field experiments. The Dang Van equivalent-stress
40
PhD student Johan
Jergéus (doctorate
earned in January
1998) in project
MU3. Photo taken
in 1997. For a photo
of Professor Roger
Lundén, see page 61
Materials and maintenance – Material och underhåll (MU) – Werkstoff und Unterhalt – Matériaux et entretien
for the calculation of stresses in a material undergoing
phase transformations. Transformation plasticity and
plastic hardening memory loss during phase transformations
were studied. The models were implemented in a
commercial finite element (fe) code. New and better
guidelines were proposed for the turning of wheels with a
flat. See also charmec’s Biennial and Triennial Reports for
Stages 1, 2 and 3.
MU4. PREDICTION OF LIFETIME OF RAILWAY WhEELS
criterion is applied in the calculation of fatigue damage of
a material volume in a multi-axial stress field with rotating
principal directions. Statistical simulations, through use
of a neural network, supplement wlife and speed up the
computer runs. It was found that rolling contact fatigue
of railway wheels is mainly related to the combination of
peak loads (overloads) and a local decrease (because of
local defects) in the fatigue resistance. See also charmec’s
Biennial and Triennial Reports for Stages 1, 2 and 3 and
the following projects mu9, mu10, mu19, mu20, mu21, mu22
and mu27 with continued research in the same area.
Anders Ekberg has been employed as senior researcher
at Chalmers Solid Mechanics (now Applied Mechanics)
since April 2000, where he has worked in close co-operation
with Dr (now Docent) Elena Kabo. In August 2005,
Anders Ekberg was appointed Docent, see page 106.
For a photo of Anders Ekberg and Roger Lundén, see
page 61.