This document summarizes a study on fatigue failures in rail steels. It discusses three main modes of failure in rail metals: fatigue, corrosion, and stress corrosion cracking. Fatigue is caused by repeated cyclic loading and can lead to microscopic cracks forming over time. The document then details the chemical composition and microstructure of typical rail steel. It examines the three stages of fatigue failure in rail steel: crack initiation due to inclusions, crack growth perpendicular to the stress axis, and final fracture. Various non-destructive testing methods for analyzing failures are also reviewed, along with recommendations to improve rail steel quality and performance.

1. V. Rahul, B. Bhaskar, G.RaviShanker
Study on Fatigue failures in Rail Steels
22/01/2017
MAHATMA GANDHI INSTITUE OF TECHNOLOGY
Hyderabad
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Introduction
Modes of Metallurgical failure in Rail metals and alloys
By Stress By Corrosion By Stress and Corrosion
Fatigue
(Mechanical)
Corrosion cracking
(Environmental)
Stress corrosion
cracking
Causes-
By repeated and
cyclic loading
Causes-
Due to Environmental
condition
Causes-
By cyclic loading on the
Corroded component

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Fatigue fracture
 Role of Fatigue
Fatigue is the weakening of a material caused by
repeatedly applied loads. however, the fatigue damage
was almost unavoidable On the other hand, usually the
fatigue damage cannot be easily detected due to the
complicated working situations of a component.
Mechanism
Essentially, there are two possible classes of
fatigue mechanisms (where failure is associated with a
dominant crack)

4. Fatigue fracture mechanisms
Intrinsic mechanisms
crack advance results from damage
processes in the crack-tip region, which
are unique to cyclic loading.
Extrinsic mechanisms
Crack propagates and causes the crack
growth and leads to fracture.
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5. Fatigue fracture-Reasons
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When a load is placed on a piece of metal, the metal
expands slightly until the load is released. The
expansion and contraction of the metal as loads are
added and removed causes microscopic cracks to
appear in the surface of the metal. As the metal is
subject to more and more cyclical loading, the cracks
get larger and larger, and eventually reach a critical size
at which they tear the fabric of the metal.

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Rail Steel
 Chemical Composition
 Microstructure
Elements C Mn Si S P V
Composition 0.74 0.96 0.68 0.0035 0.016 0.062
Optical micrograph of pearlitic railsteel showing the lamella structure

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Fatigue failure in rail steel
Fracture mechanics
Fatigue of materials can be described as having three stages.
1.Crack nucleation
2. Crack-growth, and
3. Ultimate ductile failure.
1. Crack nucleation
a) Due to presence of metallic
and Non-metallic inclusion, crack is
nucleated and the fatigue crack tends to
Propagate initially along slip planes.
b)1st stage: 45 angle to the stress axis

8. Fatigue failure in rail steel
2. Stage II Crack-growth
a) The growth of the well-defined
Crack in direction normal to
the maximum tensile stress
b) The fracture surface of stage II
Crack propagation frequently
Shows a pattern of fatigue
Striations.
C) 2nd stage: perpendicular
to the stress axis
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9. Fatigue failure in rail steel
3. Fracture
a) Due to unstable Fatigue cracks of stage II
that’s leads to failure of component
b) In this region, the fracture can be either
Brittle or Ductile depending on mechanical
Properties of material and loading
condition of materials
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10. Macroscopic analysis
Fig:--The macroscopic
morphologies of the failed
railway rail.
(a) The front view,
(b) the lateral view,
(c) the macroscopic
morphology of the rail
bottom, and
(e) the chevron patterns
and crack origin at the
fracture surface of
rail bottom.
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Microscopic analysis

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Failure analysis through NDE
Non-destructive analysis
The types of flaws/defects and degradation occurring in rolling
stock components that can be detected using NDT are summarized as
Visual
Simplest, fastest, economical and most commonly used
test to detect, defects on the surfaces Porosity,
blow holes, exposed inclusions, un fused welds
Surface cracks
Magnetic Particle
Magnetic particle Inspection process for detecting surface and slightly
subsurface discontinuities in Ferromagnetic materials such as iron, nickel, cobalt,
and some of their alloys. The process puts a magnetic field into the part.

13. Ultrasonic testing
High frequency sound waves are introduced into a material and they are reflected
back from surfaces or flaws.
Reflected sound energy is displayed versus time, and inspector can visualize a
cross section of the specimen showing the depth of features that reflect sound.
plate
crack
0 2 4 6 8 10
initial
pulse
crack
echo
back surface
echo
Oscilloscope, or flaw
detector screen
Failure analysis through NDE

14.  Liquid Penetrant Inspection (LPI)
Widely applied and low-cost inspection
method used to locate surface-breaking
defects in all non-porous materials.
LPI is used to detect casting, forging and
welding surface defects such as hairline
cracks, surface porosity, leaks in new
products, and fatigue cracks on
in-service components.
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Failure analysis through NDE

15. SCHEMATIC REPRESENTATION OF THE TYPICAL STAGES
OF THE FATIGUE DAMAGE PROCESS
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A,B,C,D are
the different material

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Recommendations
 The quality of production and processing must be
improved to reduce the defects.
 using the bainitic rail steels that can reduce
cracking and enhance Abrasion and impact
resistances in the components.
 practicing the better welding process to reduce
the entrapment of gases and metallic inclusions.
 Regular inspection of components and
replacing them.

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Literature reviewed
1. FRACTURE AND FATIGUE CRACK GROWTH ANALYSIS OF RAIL
STEELS
Heshmat A. Aglan and Mahmood Fateh
2. Fatigue of metal Fatigue of metals
Suranaree University of Technology , Tapany Udomphol
3. The Welding Institute, Granta Park, Great Abington, Cambridge.
4. A failure study of the railway rail serviced for heavy cargo trains
Y.D. Li a,b,*, C.B. Liu c, N. Xu a, X.F. Wua, W.M. Guo a, J.B. Shi a
5. Fatigue of high strength steels
Antti Järvenpää 2012

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Thanks for your attention
and
we look forward to your
valuable suggestions!