Rail Grinding Study
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Applied mechanics (MPAME), MSc
Materials engineering (MPAEM), MSc
Materials engineering (MPAEM), MSc
Publicerad
2024
Författare
Börjesson, Maria
Emanuelsson, Per
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
During maintenence grinding of pearlitic railway, the microstructure of the rails’
surface layer can transform into martensite. This can have detrimental effects, such
as crack formation, due to the brittleness of martensite. To investigate this phenomenon,
an industrial grinding machine was used to grind the surface of specimens
extracted from rail heads of two different rail grades. These were subsequently
examined to see how different grinding parameters contribute to the martensite formation.
Among other things, the thickness of the martensite layers was measured,
the shape of the layers was examined and hardness in the heat affected region was
measured.
The main takeaway from this study was that the thickness of the martensite layers
decreased with an increased feedrate caused by the shorter contact time between
grinding wheel and surface at higher feedrates. This motivates using a high train
speed during railway grinding in-field. Several additional discoveries were made during
examination. Surface discoloration correlated to different feedrates was found
on the ground specimens’ surfaces. A slight fluctuation in martensite layer thickness
along the grinding direction was discovered and deemed to be caused by oscillations
of the grinding wheel with each revolution. Tests also revealed that the difference
in hardness between martensite layers formed in the two different rail grades was
smaller than the initial hardness difference of the original pearlitic microstructures.
Simulations of the process were made using the finite element method and analytical
formulas, in an attempt to estimate the martensite layer thickness. This proved difficult
and could only be done by tuning of the energy input to match the computed
martensite thickness with the experimentally measured thickness. Further research
is needed to predict the martensite layer thickness.
Beskrivning
Ämne/nyckelord
grinding , rail , railway , martensite , pearlite , tempered martensite , hardness , finite element analysis , white etching layer (WEL)