Defect formation problems
in wheel-rail steam
A. G. Petrakova
Omsk State University of
Railway Communication, 35 pr. Marksa, Omsk, 644046, Russia
E-mail: petra-anna@yandex.ru
ABSTRACT
This
work presents the reasons of the freight cars wheels and rails defect
formation. The main ways of decreasing defect formation are presented in the
article as well.
Keywords: Wheel, rail, defect
formation, optimization, wear resistance
1.
Introduction
The
major priorities for JSC RZhD is the perspective train-passing development at
the guaranteed traffic safety and the increasing of overall performance on the
basis of track maintenance and rolling stock interaction. For its realization
it is necessary [1]:
-
to provide notable increase of weight and speed of train movement,
-
increase in running and axial loading of a rolling stock,
-
to pass to the models of driving that are most favorable from the point of view
of the energy saving,
-
to reduce the material and power losses connected with wear of wheel rail
system friction.
These
problems are considered to be the main in rolling stock service.
One
of the consequences of increasing in axial loadings is inability of wheels and
the rails made of steel of traditional brands, to correspond to new quality
standards. The operation resource and reliability of rubbing wheel rail pair in
most cases are defined by a condition of driving of a wheel and a rail head.
The traffic safety of a rolling stock depends on these defects of the surface.
2. Main defects and reasons
For
the railroads working in the conditions of heavy movement when axial loading is
in limits of 23,5 — 30 t, interaction problems now are [2, 6, 8, 10]:
•
contact fatigue damages of wheels and rails, including thermomechanical
damages;
•
formation of wheel roll in form of a through wave;
•
plastic deformation of wheel and rail working surfaces;
•
splitting off of a wheel rim;
•
descents because of a wheel wave on a rail;
•
break of a rail and destruction of rails in a zone of a welded joint.
Wear
and damage reduce resistance of detail fatigue and can be the reason of their
destruction even at insignificant concentrators of tension and very low rated
voltage [3].
Researches
wheel and rail surface damages of different types and nature of destruction
give the grounds to claim that destructions are a consequence of a large number
of the reasons which generally depend on physicomechanical properties,
violations in manufacturing techniques and repair, a tension in a place of
destruction and dynamic loadings.
3. Ways of decreasing defect formation
Having
defined the main reasons for defect formation in wheel rail steam it is
possible to allocate the following perspective ways of decrease:
- the design
They are directed on constructive
changes in wheel rail steam,
- the all-technical
They are directed on development of
additional stages of production, operation and repair quality control.
- the technological
They are connected with modification
of technological process of production or repair.
In
the design direction three main ways of decrease in defect formation in wheel
rail steam are allocated: the reduction of relative slipping, the tension
reduction in a contact zone, the improvement of a technical condition of brake
system.
For
the management of wheel and the rails blanket properties are providing good
contact in a wheel rail steam, and the reduction of relative slipping the
introduction of «the third body» is carried out (Lubrication for wheel wave
contact zone with lateral surface of a rail head and use of friction activators
for coupling of locomotives in a draft mode increase).
Decrease
in tension in a zone contact "wheel rail" is the difficult task
connected with determination of the sizes of a spot of the contact and contact
tension. At reduction of the area of a spot of the contact the size of contact
tension starts growing, surpassing a limit of fluidity of wheel steel. With
increase in loading at a wheel this process amplifies, besides separate sites
are excessively overloaded that leads to formation of superheated zones and
undesirable consequences. If the overheat reaches recrystallization
temperature, the decrease of hardness of such site is inevitable.
The
size and distribution of contact tension significantly depend on wheel and rail
profiles and on what contact takes place. But at the solution of this task
optimization of a seamless-rolled wheels profile combined with operational
profiles of rails is necessary. However the profile has been changed only once
towards the reduction of thickness of a wheel crest [5].
One
more design measure is decrease of defects of a brake origin in quantity. For
this purpose it is necessary to carry out the improvement of a brake system
technical condition, the improvement of a material and a design of blocks, the
mechanization of hump yards [7, 9].
All-technical
actions include quality control of repair and production modern
diagnostics of a driving surface condition of wheels, introduction of devices
finding wheel defects and also development of a way to recognize the size of
defects at their diagnosing [4].
The
complex of technological measures has to be directed on improvement of wheel
repairing (economic turning of wheel couples and increase of its quality,
creation of informational system for the analysis of defects, time and the
reasons of wheel couple turning), and also on increase of material firmness of
a wheel to defect formation. The most perspective at this stage is hardening of
a driving surface of a wheel.
4. Conclusion
Until
recently JSC RZhD management most often tried to eliminate harmful consequences
of high axial loadings at the expense of improvement of the equipment by
greasing of working surfaces of wheels and rails, and also using high-strength
steel at production of wheels [9, 11]. These measures though reduced rate of
wear, but increased quantity of other defects on working surfaces both wheels
and rails. The integrated approach, carrying out scientific researches and
considerable investments is necessary for decreasing defect formation in wheel
rail steam.
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