The
steel wheel for a freight car has three basic functions
Figure 2. A wheel is rolled in the new vertical wheel rolling mill. Note that there is no mandrel.
i.
To act as
a brake drum
ii.
To support
the weight of the car and it cargo
iii.
To guide
the freight car on the rails
Freight
car wheels are produced by either casting or rotary forging. They are subjected
to complex condition of dynamic thermal and mechanical stresses. Safety is of
great importance, since derailment can cause loss of life and property. Develop
a broad systems approach to the design of an
improved cast steel car wheel.
Solution
1. Problem
Our
target is to develop a broad systems approach to the design of an improved cast steel car wheel.
2. Problem
Discussion
What are the problems usually faced by the steel
wheel of a freight car?
The problems that founded here are:
i.
Brake fade problem
ii.
Heat issues
iii.
Squealing issues
3. Problem
Statement
Design a solution for the improved car steel wheel
to be used I a good and safe system. The solution will be focused on the brake
fade improvement, heat distribution issues and the squealing issues which are considered
in thermal and mechanical stresses concept.
4. Problem analysis
We first need to determine the types of brake system
that suitable for the freight car wheels that will give the optimum solution to
reduce the yields of friction and wear of the wheel. Then, the heat produced
during the run also will be considered due to has a durable mechanical and
material structure of the wheel and finally we will focused on the squealing
noise issues that can solve the environmental problem of the residents that
live around the railway station.
4.1 Brake
fade problem
4.2 Heat Distribution Issues on the Wheels
4.2.2 Recognition
of Need
In the nineteenth century, following the development of industrial
production, needs raw materials and called for the creation of vehicles with
higher capacity, powerful, reliable in operation and providing increased speed.
As in any other field, safety comes first, whether it is passenger or, equally,
on freight transportation. From the early days of rail transport has
significant emphasis on improving quality, and, last but not least, the safety.
Being in fierce competition, continuous and long-term with other means of
transport, modern rail transport has an important share in most countries
worldwide with an increasing trend in traffic speeds, hauled tonnages and
offered competitive costs. Continuous growth of velocity on the railway imposed
special security issues regarding guiding rail safety in general. One of the
problems in the operation of railway vehicles equipped with wheels with
bandages and brake blocks is the appearance of bandages rotating on disk.
4.2.3 Problem
Train braking is a very complex process, specific to rail vehicles
and of great importance by the essential contribution on the safety of the
traffic. This complexity results from the fact that during braking occur
numerous phenomena of different kinds - mechanical, thermal, pneumatic,
electrical, etc. The actions of these processes take place in various points of
the vehicles and act on different parts of the train, with varying intensities.
The major problem is that all must favorably interact for the intended scope,
to provide efficient, correct and safe braking actions.
The purpose of braking action is to perform controlled reduction in
velocity of the train, either to reach a certain lower speed or to stop to a
fixed point. In general terms, this happens by converting the kinetic energy of
the train and the potential one - in case of circulation on slopes - into
mechanical work of braking forces which usually turns into heat, which
dissipates into the environment.
Heat lead to the expended of the wheel which affect the bearing.
Thus the train will get the problem in a long term. Life circle for the bearing
become shorter.
4.2.4 Concept
Design
Rotary Furnace
After cutting
and weighing, blocks are segregated by heat numbers and are charged into the
rotary hearth furnace. The furnace burns natural gas, with oil as a backup
alternative, to heat the wheel blanks to the required forging temperature. The
furnace has five sequential heating zones, starting at 1600°F and graduating to
2300°F in the final zone before forging. This new computer controlled,
state-of-the-art furnace has regenerative burners that provide improved
efficiency.
Descaler
The blocks are removed
from the rotary heating furnace at a temperature of 2300°F and are placed on
top of the descaler unit. An elevator lowers the block into the descaler and
the block is blasted with high-pressure water to remove the iron oxide scale
before forging. This process step is performed to prevent the occurrence of
entrapped scale on the final forged surface. Once the mult has been descaled,
the robot manipulator grips the block and places it on the table of the
10,000-ton forging press. 10,000 ton
forging press
When the manipulator releases the block on the first operation
table, computer control of the two stage forging operation begins. The
10,000-ton forging press provides the pre-form shape for later rolling and
begins the transformation into the more recognizable finished product, the
railroad wheel. The first operation of the press uses a flat bottom die and
only the top of the block is shaped. After the first operation is completed,
the bottom table slides to locate the second operation die in position for the
second forge hit. This second operation provides for shaping of the pre-form
bottom. The 10,000-ton forging press was completely refurbished as part of the
wheel mill modernization project. Hydraulics and structural components were
rebuilt and press control systems were updated. After the pre-form is completed
on the 10,000 ton forging press, the piece is removed from the press with a
robot manipulator, and passed to a second robot manipulator for insertion into
the new Wagner vertical wheel rolling mill.
 |
| Figure 1. A robot manipulator transferring a wheel pre-form from the 10,000 ton forging press to the rolling mill |
Vertical Wheel Rolling Mill
The new rolling mill is the most
modern in the world and is capable of producing the world's most precise forged
railroad wheel. The state-of-the-art, computer controlled, rolling mill
continues the transformation process by means of various rollers. Web rolls,
which perform the driving function to rotate the wheel during rolling, contact
the pre-form in the plate area. The mill back roll, in combination with other
tooling such as web rolls, upper and lower centering rolls, conical edging
rolls and guide rolls, provides the forces responsible for shaping the perform
into a wheel. Wheel rolling is now accomplished without a mandrel through the
center of the wheel.
The computer controls on the
rolling mill ensure that a consistent rolled product is produced. However,
extensive effort went into the initial set-up process of the mill for each of
the many different wheel designs produced by Standard Steel. Rolling mill
computers were adjusted to insure dimensional quality and numerous trial
production runs were conducted following mill installation and shake-down. All
wheel designs have been converted to the new process.
Figure 2. A wheel is rolled in the new vertical wheel rolling mill. Note that there is no mandrel.
The diameter of the pre-form is expanded significantly during the
rolling process and the diameter is monitored using a laser measuring system
that is focused on the tread. In addition to the laser, there are thirteen
position control indicators and twenty-six pressure transducers involved in
controlling the mill tooling to obtain correct rolled dimensions in the
finished product. When the wheel reaches the values specified for the wheel
design being produced, rolling automatically stops. The mill edging rolls, side
rolls and centering rolls insure that a uniform, concentric wheel with the
required flange is produced. Rolling time is less than one minute per wheel.
Following rolling, the wheel is inserted into the 4,000 ton dishing and
punching press by a robot manipulator, as shown in Figure 3.
 |
| Figure 3. A robot manipulator passes a wheel from the rolling mill to the dishing and punching press. |
Dishing And Punching
This two-stage operation forges the final wheel shape. The first
operation, known as dishing, provides the wheel the modern "S" plate
design shape. This design provides much lower thermal stresses in railroad
service than the older, straight plate wheel design. The second operation is
punching, which produces a center hole for mounting the wheel on the axle.
Hydraulic and mechanical systems on this press were also upgraded to insure a
consistent final wheel product.
Automated Stamping
Following the dishing and punching operations the wheel is
transferred by robot manipulator for automated stamping of manufacturing
identification information on the wheel hub. The stamping machine automatically
indexes to the next serial number and provides for consistency in stamping.
Previously, hub stamping was done manually and workers changed stamping dies
between each wheel.
The many improvements made by Standard Steel in recent years
demonstrate the firm’s commitment to production of quality railroad wheels.
With increasing service demands in a cost-competitive marketplace, modernization
and product improvements are clearly essential.
4.3
Squealing Issues
Noise and
vibration are major sources of environmental impact due to railway operations.
4.3.1 Types of noise
i.
Squeal
noise = occurs when a terrain wagon rounds a curve of small radius.
ii.
Impact
noise = occurs when a wheel crosses a rail joint or another discontinuity in
the rail.
iii.
Rolling
noise = usually dominates on straight track, in the absence of rail joints and
wheel flats. Called surface irregularities are normally referred to as
roughness or waviness.
4.3.2 Improved design for less noise wheel
Narrow-gauge railway wheel
Typical railway
wheels have an offset on the plate for the purpose of reducing heat stress
caused by continuous braking and to reduce their weight. Also, the wheels
are classified as “corrugated” or “non- corrugated” with the
corrugated wheels having a reinforcing plate located radially and at fixed
angles (every 60°). In addition, the corrugated wheel’s plate thick- ness is
reduced to further
lessen the weight of
the wheel. Recently, the new corrugated “NA-Type” wheel, which has about 7%
less weight than a conventional “A-Type” wheel, has been used.
4.3.3 Conclusion
Combining the
3-D Scanning Laser Vibrometer data with the structural sound field analysis of
the railway wheels leads to the following two conclusions:
1. The
highest sound power comes from the wheel’s plate: 80% for corrugated NA-type
wheels with large offsets and 50% for C-type wheels.
2. Regarding
wheel shape factors, the rim is an important part of the sound power which
decreases with increasing rim thickness.
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