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SUBMITTED BY- :

NAVIN DIXIT;NAVIN

B.Tech( 3rd year)

Mechanical Engineering

IET Lucknow

2014REPORT ON SUMMER TRAINING (9 June-6 July)

RDSO(Research Design and Standard Organisation)

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INDEXS. No

Description PAGE No.

1. Acknowledgement 2

2. Introduction 3

3. Testing Directorate 4

4. Fatigue Testing Laboratory 8

5. Brake Dynamometer Laboratory 15

6. Air Brake Laboratory 20

7. Test Cell Laboratory 29

8. Conclusion 44

9. References 45

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ACKNOWLEDGEMENT

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INTRODUCTION

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TESTING DIRECTORATE

HISTORY:

After independence in the year 1952 Railway Testing and Research Centre (RTRC) was set up for carrying out Developmental Research and for investigation into Railway problems. All type of testing activities was being done by this RTRC organisation.

Present organisation RDSO was created in the year 1957 by merger of Central Standards Organisation (Simla) and Railway Testing and Research Centre (RTRC). Testing activities were then made part of Research directorate which was working under Director Research.

In the year 1989 the present Testing directorate was created for carrying out all dynamic and static mechanical testing activities of all type Railway Rolling stocks.

This directorate is looked after by Executive Director Research Testing.

This directorate undertakes design validation of all newly designed/modified rolling stock developed, in house or imported. Besides undertaking actual fields and static trials this directorate has three laboratories for conducting simulated trials on rolling stock subassemblies and its components.

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In addition to these static and dynamic filed trials this directorate is also entrusted with carrying out track monitoring and route proving runs on Shatabdi/Rajdhani and all ‘A’ routes of Indian Railways.

Laboratories and its Contribution :

Testing directorate has following testing Laboratories:

AIR BRAKE LABORATORY:

The main function of laboratory is to study and optimise train brake characteristics with different type of distributor valves, multiple locomotive operation, varying leakage rate, compressive and main reservoir capacities, effect of train parting, performance of distributor vales etc.

The laboratory is equipped with test rig having the complete pneumatic circuits of 192 Wagons and 30 coaches with twin pipe air brake system. Three locomotive controls stands can be used any where in the formation with varying compressed air flow rate up to 16Kilo litre per minute with seven compressor. The laboratory is also equipped with single car test rig and endurance test rig for distributor valves. Data acquisition and analysis is fully digitals.

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FATIGUE LABORATORY:

This laboratory is installed for fatigue testing and structural strength analysis of bogie frames and their components for rolling stocks and FRP sleepers. These are tested by simulating service loads in order to optimise the design, study of residual life of components and endurance test of rubber components etc.

The laboratory is equipped with different type of load actuators. The laboratory is also equipped with Universal Spring Testing machine.

BRAKE DYNAMOMETER LABORATORY :

The dynamometer is extensively used for type tests and performance audit tests of cast iron and composition brake blocks. Parameters commonly determined are coefficient of friction; wear rate and temperature rise in brake block and wheel. The effect of sustained down gradient and consequent application of brakes constantly, over along time is also studied. The laboratory equipped with a gyrating mass brake dynamometer supplied by M/s MAN OF GERMANY, is capable of testing up to a speed of 250 Kmph. Under simulation of axel load up to 25t, brake torque of 4800 kg-meter and brake force of maximum 6000 kg in wet and dry conditions, with continuous recording and computerized analysis of data.

TEST CELL LABORATORY:

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The field units of Testing Directorates conducts field trials for modified/new designed rolling stock as Oscillation trial, Braking trial, Rating Performance trials, Controllability Trials, coupler force trials, Compressive End Load Tests (Squeeze test) etc. along with Track Monitoring Runs.

Earlier, Testing Directorate were used Analogue Recorder and signal condition units for conducting these trials and partially starts conducting field trials with Digital Data Recording system supplied by AAR in the year of 1991 in which the digital data recording system was HP make and the acquisition program was based on Basic and Pascal language. Further analogue recording system was completely replaced to digital data recording system in the year 2003-04 in which the data acquisition card PCI-16E4 was used and installed in one the slot of PC. The analogue signals were connected to SCXI connecting card and further this card was used for analogue to digital conversion.

Further in continuous process of development the Testing Directorate have procured the new technology for modernization of testing infrastructure for field trials in which the Compact Digital data recording system, signal conditioners modules, sensors and cables etc. have been procured in the Year of 2009-10.

With the modernization of testing facilities in Testing Directorate, the accuracy of test result has been increased as well as time duration of test/trials and analysis have been reduced.

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FATIGUE TESTING LABORATORYINFRASTRUCTURE:

Facilities:• Two dynamic actuators of 150 ton capacity and two dynamic actuators of 25 ton capacity of +125 mm stroke.

• Four static actuators of 75 ton capacity of 300 mm stroke.

• 500 ton reaction frame

• Two dynamic actuators of 10 ton capacity of +50 mm stroke

• Four dynamic actuators of +25 ton capacity of +50mm stroke.

• 30 ton and 50 ton capacity reaction frame

• Frame Mounted Shock Absorber Testing Machine, with + 50KN load capacity and + 150mm stroke Hydraulic Actuator

• 96 channels on line stress measuring system.

Features:

• Structural strength of Bogie frames, Bolster & Brake beam of rolling stock

• Fatigue test of FRP sleepers for track by simulating service loads.

• Endurance test of sand-witch rubber components.

• Endurance test and damping characteristics of shock absorber.

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STRESS INVESTIGATION AND FATIGUE TEST OF BOGIE FRAME:

ABOUT THE TEST:

Newly designed bogie frames are subjected to stress investigation and Fatigue Test. The object of these tests is to determine stress levels, both in nature and magnitude, at different critical locations on the bogie frame, by simulating static and dynamic loads likely to be experienced by the bogie frame under actual service conditions. Also, the adequacy of the design of the bogie frame, from structural strength point of view is determined by applying dynamic load up to 6 or 10 million cycles, as the case may be, for conducting fatigue tests and monitoring the stresses at different critical locations.

PREPARING FOR THE TEST:

The test system basically consists of a closed loop electro-hydraulic fatigue testing equipment. It is provided with a hydraulic power supply for generating high-pressure hydraulic fluid required for producing the desired forces. The high-pressure hydraulic fluid at 210 kg/mm² is fed to the hydraulic actuator through a servo valve. The actuator, which is a cylinder with a piston, applies the compressive / tensile forces to the specimen mounted on the test bed.

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The electronic control equipment on the control panel achieves the desired level of loading. A command signal is fed to the input module that passes it on to a servo controller. A function generator provides the desired dynamic waveform. The controller sends electrical signal to the servo valve to regulate its port openings in such a manner as to achieve the desired load level. A feedback transducer, introduced in the system, senses the load applied to the specimen and sends a proportional signal to the input module. Here, the feedback is compared with the command and any difference in their magnitudes or polarity is corrected through an electrical signal to the controller. With this arrangement any continuously varying command can be faithfully reproduced.

As the load application capacity of the existing actuators of the fatigue testing equipment and number of actuators available are limited, static hydraulic jacks are used to supplement the load requirements of the tests. Load cells, manufactured locally, are used to sense the load at axle box locations.

Strain gauges to the following specifications are being used for monitoring strain / stress at different critical locations of the bogie frame-

Linear Gauge Rossette Gauge

Gauge Length 5 mm 5 mm

Gauge Resistance 120 ohm 120 ohm

Gauge Factor 2.14 2.11

Analogue pen recorders (brush) are used to monitor the loads during load equalisation and optical recorders (visicorders) are used to monitor the strains / stresses.

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A counter provided on control panel of the fatigue testing equipment is used to register the number of test cycles applied to the bogie frame.

All the fixtures, brackets and stools suitable for holding the specimens and for taking reactions, are designed and fabricated by the Testing Directorate in-house, or through railway workshops, or from the local market.

FATIGUE TESTING MACHINE

STRESS MEASUREMENTS:

The bogie is strain gauged at locations specified in the test scheme, which are mostly linear gauges and a few three-directional Rossette gauges. Each gauge (the arm in the case of Rossette gauges) fixed on the bogies frame, functions as an active arm of Wheatstone bridge for monitoring the strain / stress. The remaining three gauges required to form the Wheatstone bridge, called the dummy gauges, are cemented on steel strips mounted on a junction box, kept close to the bogie frame during the course of the tests. Terminals of the bridge, thus formed, are connected to the recorder (visicorder). During the stress recording in static condition, the bogie is subjected to the desired

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load combinations and three sets of readings are taken for every load combination. It is generally noticed that the difference between the three readings is practically negligible. Before conducting the dynamic stress measurement, the bogie frame is subjected to the desired load combinations for at least for 3 to 5 minutes and

thereafter, the readings are taken.BOGIE FRAME

FATIGUE TEST:

The bogie frame is subjected to fatigue test by applying dynamic load combinations as per test scheme. The load application is of sinusoidal nature, which is achieved with the help of the function generator available with control panel of the fatigue testing equipment. Fatigue tests are carried out upto 10 million cycles. The test frequency, with the stablised test set up, is achieved as 3 to 4 Hz.

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All the dynamic load actuators are applying load at the same frequency and in the same phase.

VERTICAL LOAD APPLICATION AND REACTION:

The bogie frame is placed on the four vertical stools clamped with the test bed. The loading is done with the help of load actuators, each with the capacity of +10 or 25 t mounted on the two separate main reaction frames capable of bearing 30 or 50 t force and located longitudinally on both the sides of test bed, through two loading beams placed at the ends of bolster which, in fact, is kept on two specially designed steel tubes (in place of secondary springs) placed in the spring seat guide located in the middle of the side frames.

Reaction of the vertical load at axle box location is attained through fabricated steel tubes placed between the bogie frame and vertical stool at all the four locations. Specially designed load cells, one each at all the four axle box locations, are inserted between the stool and the steel tubes for equalizing the load distribution.

TRANSVERSE LOAD APPLICATION AND REACTION:

A U-type clamp is mounted in the middle of the one of the side frames on the existing bracket welded to the bogie frame. The transverse load is applied centrally with the help of the +10 t capacity dynamic actuators, held horizontally on the specially designed brackets mounted on the test bed.

Transverse reaction is taken at all the axle box locations by suitable reaction brackets clamped on the test bed.

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TRACTIVE LOAD / BRAKING FORCE AND REACTION:

Longitudinal loads, simulating tractive / braking load and their reactions, are applied on the bogie frame separately. For the purpose of braking force, loads are applied simultaneously at four brake hanger locations, through two static jacks in the upward direction, and through two pre-calibrated helical springs in the downward direction. The tractive / braking loads are applied on the two anchor links in the same direction through two static jacks mounted horizontally on the two brackets, and their reactions are taken in the opposite direction at the end of each side frame.

VISUAL EXAMINATION:

Visual examination of the bogie frame is to be done regularly throughout the test to check if any crack or deterioration in the bogie frame, has got developed.

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BRAKE DYNAMOMETER LABORATORYINFRASTRUCTURE:

The laboratory equipped with a Gyrating Mass Brake Dynamometer supplied by M/s MAN of Germany, is capable of testing up to a speed of 250 km/h under simulation of axle load up to 25 t, brake torque of 4800 kg-m and brake force of maximum 6000 kg in wet and dry conditions, with continuous recording and computerised analysis of data.

TYPE ACCEPTANCE TEST OF BRAKE BLOCKS:

PHYSICAL CHECK:

After the receipt of the brake block samples in the laboratory, these are registered and identification numbers are stamped on each brake block. These brake blocks are physically checked to ensure that they match the wheel profile of the rolling stock for which testing is to be done.

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GYRATING BRAKE DYANAMOMETER

BEDDING:

The brake blocks are fixed on the dynamometer for bedding to achieve about 80% of the block contact area. This exercise is necessary to have a uniform distribution of brake blocks force over the full brake block area during the tests. Bedding of the brake block is done at a speed of 60 km/h and with a brake block force of 1500 kg.

During bedding a wheel temperature of 20 to 60 deg. C is maintained. After the contact area of the brake block is bedded to about 80%, tests are started under dry condition.

DRY TESTS:

Brake blocks are tested under dry condition at speeds of 20 to 140 km/h with an increment of 20 km/h with a brake block force as per test scheme. Three applications are made at each speed. The wheel temperature of 60 to 120 deg. C is maintained, as far as possible, before each brake application.

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After switching on the system, the DC motor is first run at slow speed. The motor is then accelerated to the desired rpm, corresponding to the required speed. The motor rpm is kept slightly higher than the required braking speed. After attainment of the slightly higher rpm, motor is switched off and brakes are applied at corresponding speed with the help of brake-on switch provided on the control desk. Blower fan, at a speed of 750 rpm, is normally kept running during the tests.

Various parameters e.g. braking speed, braking time, run out revolution, brake energy and mean coefficient of friction, are recorded on the data acquisition system.

Iron-constantin thermocouples are embedded on the brake blocks to monitor the brake block temperature.

Wheel temperature is, however, measured with a highly sensitive contact less sensor mounted almost at the top of wheel tread, close to the rubbing surface. This temperature is digitally displayed.

At the end of the test the brake blocks are inspected for cracks, chipping, flaking, hot spot and metallic inclusion. Wheel is also checked for any abnormality.

Brake blocks are weighed for wear, before and at the end of each brake block force applied, during the dry tests.

WET TESTS:

After completion of dry tests, wet tests are conducted on the same set of brake blocks at the same speed and brake forces as dry tests.

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Continuous flow of water at the rate of 14 litres per hour is allowed to fall on the top of the wheel through small nozzles of 1 mm diameter during wet test. It simulates the rainy season conditions.

During wet tests, blowers are not used, to avoid water falling on the top of the wheel, from flying away.Acceleration, running and braking at desired force and wheel temperature are done in the same manner as the dry tests.

Brake blocks are weighed for wear, before and at the end of each brake block force, during the wet tests.

After completing the wet tests, inspection of both wheel and brake blocks is done for any abnormality.

BRAKE BLOCK SAMPLES FOR TESTING

DRAG TEST:

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After dry and wet tests on the brake blocks are over, all the samples are subjected to the most severe type of braking, simulating the controlling of the train on the ‘ghat’ section by application of brakes continuously.

The brakes are kept applied on the wheel for 20 minutes without switching off the motor at a constant speed of 60 km/h. During drag tests, torque equivalent of about 45 BHP is maintained. For maintaining constant torque, the brake force on the brake block is kept on changing. The temperature of the wheel and brake block is recorded at every 100 seconds. At the end of 20 minutes, maximum temperatures attained by the wheel and brake blocks are recorded. In case of brake blocks catching fire, or any abnormality observed in course of testing, further drag testing is stopped.

Immediately after the test, motor is shut off and brake block force is increased to a level specified in the test scheme and brakes are applied and various brake characteristics are studied. During drag tests, phenomena like emission of smoke and spark, formation of red band and flaming etc. are recorded. At the end of the test, inspection of the wheel and brake block is done to see any abnormality on the wheel and brake blocks.

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AIR BRAKE LABORATORYINFRASTRUCTURE:

The laboratory is equipped with a Test Rig having the complete pneumatic circuits of 192 wagons and 30 coaches with twin pipe air brake system. Three locomotive control stands can be used anywhere in the formation, with varying compressed airflow rate up to 16 kl per minute with the help of 7 compressors. Data acquisition and analysis is completely computerised. The laboratory is equipped with a single car test rig and an endurance test rig for distributor valves.

AIR BRAKE LABORATORY

Background:

Prior to the introduction of air brakes, stopping a train was a difficult business. In the early days when trains consisted of one or two cars and speeds were low, the engine driver could stop the train by

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reversing the steamflow to the cylinders, causing the locomotive to act as a brake. However, as trains got longer, heavier and faster, and started to operate in mountainous regions, it became necessary to fit each car with brakes, as thelocomotive was no longer capable of bringing the train to a halt in a reasonable distance.

The introduction of brakes to railcars necessitated the employment of additional crew members called brakemen, whose job it was to move from car to car and apply or release the brakes when signaled to do so by the engineer with a series of whistle blasts. Occasionally, whistle signals were not heard, incorrectly given or incorrectly interpreted, and derailments or collisions would occur because trains were not stopped in time.

Brakes were manually applied and released by turning a large brake wheel located at one end of each car. The brake wheel pulled on the car's brake rigging and clamped the brake shoes against the wheels. As considerable force was required to overcome the friction in the brake rigging, the brakeman used a stout piece of wood called a "club" to assist him in turning the brake wheel.

The job of a passenger train brakeman wasn't too difficult, as he was not exposed to the weather and could conveniently move from car to car through the vestibules, which is where the brake wheel was (and still is, in many cases) located. Also, passenger trains were not as heavy or lengthy as their freight counterparts, which eased the task of operating the brakes.

A brakeman's job on a freight train was far more difficult, as he was exposed to the elements and was responsible for many more cars. To set the brakes on a boxcar (UIC: covered wagon) the brakeman had

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to climb to the roof ("coon the buggy" in railroad slang) and walk a narrow catwalk to reach the brake wheel while the car was swaying and pitching beneath his feet. There was nothing to grasp other than the brake wheel itself, and getting to the next car often required jumping. Needless to say, a freight brakeman's job was extremely dangerous, and many were maimed or killed in falls from moving trains.

Complicating matters, the manually operated brakes had limited effectiveness and controlling a train's speed in mountainous terrain was a dicey affair. Occasionally, the brakemen simply could not set enough brakes to a degree where they were able to reduce speed while descending a grade, which usually resulted in a runaway—followed by a disastrous wreck.

When adopted, the Westinghouse system had a major effect on railroad safety.Reliable braking was assured, reducing the frequent accidents that plagued the industry. Brakemen were no longer required to risk life and limb to stop a train, and with the engineer now in control of the brakes, misunderstood whistle signals were eliminated. As a result, longer and heavier trains could be safely run at higher speeds.

During his lifetime, Westinghouse made many improvements to his invention. The United States Congress passed the Safety Appliance Act in 1893 making the use of some automatic brake system mandatory. By 1905, over 2,000,000 freight, passenger, mail, baggage and express railroad cars and 89,000 locomotives in the United States were equipped with the Westinghouse Automatic Brake.

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The set-up in the laboratory consists of-

192 BOXN wagon twin / single pipe air brake equipment 30 coach passenger twin pipe air brake equipment 7 compressors with total capacity upto 16000 lts/m Computersied data acquisition and analysis 3 portable locomotive control stands Single car test device 16 reservoirs of 200 litres capacity each Air dryers to supply dry compressed air to the system Distributor valve test rig Endurance test rig for distributor valves Test rig for brake cylinder Simulation for train parting by solenoid valve Locomotive compressed air dryer

TESTS BEING CONDUCTED:

Brake characteristics for the following types of train formations and train brake equipment are being carried out by the laboratory-

Freight train upto 192 BOXN wagons with single or twin pipe Passenger train upto 30 coaches Effect of leakage on release of brakes Optimum compressor and reservoir capacity for various train lengths Effect of over charge feature on train operation Indication to drivers in case of train parting Optimum location of locomotives in long freight train

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Effect of change in design of locomotive brake system on train brake performance

Effect of distributor valve design changes on train brake characteristics

Brake characteristic of passenger train with locomotives at both ends Performance testing of distributor valves

BRAKE TESTING SET UP

Overview:

In the air brake's simplest form, called the straight air system, compressed air pushes on a piston in a cylinder. The piston is connected through mechanical linkage to brake shoes that can rub on the train wheels, using the resulting friction to slow the train. The mechanical linkage can become quite elaborate, as it evenly distributes force from one pressurized air cylinder to 8 or 12 wheels.

The pressurized air comes from an air compressor in the locomotive and is sent from car to car by a train line made up of pipes beneath each car and hoses between cars. The principal problem with the straight air braking system is that any separation between hoses and pipes causes loss of air pressure and hence the loss of the force applying the brakes. This deficiency could easily cause a runaway

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train. Straight air brakes are still used on locomotives, although as a dual circuit system, usually with each bogie (truck) having its own circuit.In order to design a system without the shortcomings of the straight air system, Westinghouse invented a system wherein each piece of railroad rolling stock was equipped with an air reservoir and a triple valve, also known as a control valve.

The triple valve is described as being so named as it performs three functions: Charging air into an air tank ready to be used, applying the brakes, and releasing them. In so doing, it supports certain other actions (i.e. it 'holds' or maintains the application and it permits the exhaust of brake cylinder pressure and the recharging of the reservoir during the release). In his patent application, Westinghouse refers to his 'triple-valve device' because of the three component valvular parts comprising it: the diaphragm-operated poppet valve feeding reservoir air to the brake cylinder, the reservoir charging valve, and the brake cylinder release valve. When he soon improved the device by removing the poppet valve action, these three components became the piston valve, the slide valve, and the graduating valve.

If the pressure in the train line is lower than that of the reservoir, the brake cylinder exhaust portal is closed and air from the car's reservoir is fed into the brake cylinder to apply the brakes. This action continues until equilibrium between the brake pipe pressure and reservoir pressure is achieved. At that point, the airflow from the reservoir to the brake cylinder is lapped off and the cylinder is maintained at a constant pressure.

If the pressure in the train line is higher than that of the reservoir, the triple valve connects the train line to the reservoir feed, causing the air pressure in the reservoir to increase. The triple valve also causes the brake cylinder to be exhausted to the atmosphere, releasing the brakes.

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As the pressure in the train line and that of the reservoir equalize, the triple valve closes, causing the air pressure in the reservoir and brake cylinder to be maintained at the current level.

Unlike the straight air system, the Westinghouse system uses a reduction in air pressure in the train line to apply the brakes. When the engineer (driver) applies the brake by operating the locomotive brake valve, the train line vents to atmosphere at a controlled rate, reducing the train line pressure and in turn triggering the triple valve on each car to feed air into its brake cylinder. When the engineer releases the brake, the locomotive brake valve portal to atmosphere is closed, allowing the train line to be recharged by the compressor of the locomotive. The subsequent increase of train line pressure causes the triple valves on each car to discharge the contents of the brake cylinder to the atmosphere, releasing the brakes and recharging the reservoirs.

Under the Westinghouse system, therefore, brakes are applied by reducing train line pressure and released by increasing train line pressure. The Westinghouse system is thus fail safe—any failure in the train line, including a separation ("break-in-two") of the train, will cause a loss of train line pressure, causing the brakes to be applied and bringing the train to a stop, thus preventing a runaway train.Modern air brake systems are in effect two braking systems combined:

The service brake system, which applies and releases the brakes during normal operations (generally referred to as the independent brake), and

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The emergency brake system, which applies the brakes rapidly in the event of a brake pipe failure or an emergency application by the engineer (generally referred to as the automatic brake).When the train brakes are applied during normal operations, the engineer makes a "service application" or a "service rate reduction”, which means that the train line pressure reduces at a controlled rate. It takes several seconds for the train line pressure to reduce and consequently takes several seconds for the brakes to apply throughout the train. In the event the train needs to make an emergency stop, the engineer can make an "emergency application," which immediately and rapidly vents all of the train line pressure to atmosphere, resulting in a rapid application of the train's brakes. An emergency application also results when the train line comes apart or otherwise fails, as all air will also be immediately vented to atmosphere.

In addition, an emergency application brings in an additional component of each car's air brake system: the emergency portion. The triple valve is divided into two portions: the service portion, which contains the mechanism used during brake applications made during service reductions, and the emergency portion, which senses the immediate, rapid release of train line pressure. In addition, each car's air brake reservoir is divided into two portions—the service portion and the emergency portion—and is known as the "dual-compartment reservoir”. Normal service applications transfer air pressure from the service portion to the brake cylinder, while emergency applications cause the triple valve to direct all air in both the service portion and the emergency portion of the dual-compartment reservoir to the brake cylinder, resulting in a 20–30% stronger application.

The emergency portion of each triple valve is activated by the extremely rapid rate of reduction of train line pressure. Due to the

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length of trains and the small diameter of the train line, the rate of reduction is high near the front of the train (in the case of an engineer-initiated emergency application) or near the break in the train line (in the case of the train line coming apart). Farther away from the source of the emergency application, the rate of reduction can be reduced to the point where triple valves will not detect the application as an emergency reduction. To prevent this, each triple valve's emergency portion contains an auxiliary vent port, which, when activated by an emergency application, also locally vents the train line's pressure directly to atmosphere. This serves to propagate the emergency application rapidly along the entire length of the train.

Use of distributed power (i.e., remotely controlled locomotive units midtrain and/or at the rear end) mitigates somewhat the time-lag problem with long trains, because a telemetered radio signal from the engineer in the front locomotive commands the distant units to initiate brake pressure reductions that propagate quickly through nearby cars

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TEST CELL LABORATORYIntroduction:

Oscillation trial is conducted on a new or modified design of rolling stock, which is proposed to be cleared for running on IR track. The purpose of oscillation trial is, thus, an acceptance of a railway vehicle by conducting dynamic behaviour tests in connection with safety, track fatigue and quality of ride.

‘Policy Circular No.6’ issued vide ME/Railway Board letter No. 92/CEDO/SR/4/0 Pt. dated 23.12.1999 (refer chapter XIV) and Third criteria report of ‘Standing Criteria Committee’ issued in January’2000 and amendment no. RM2/MCI/21 dated 10.07.2000 (refer chapter XV) are the two reference documents based on which an oscillation trial is conducted.

An oscillation trial can be commenced only after receipt of CRS sanction. CRS sanction is accompanied by Joint Safety Certificate from the Railway and Speed Certificate issued by RDSO. In addition, documents like, ‘List of curves and bridges’, ‘Permanent and temporary speed restrictions’ on the route from the railway applicable on the day of run, ‘Test scheme’ from the sponsoring/design directorate and latest summarised ‘TRC results’ for selected detailed test stretches are needed to conduct the trials.

The ‘test scheme’ includes objective of trial, background of trial, various trial conditions, measurements and parameters to be recorded, design particulars of the test vehicle, load vs. deflection

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charts for individual and nested springs, necessary drawings of bogie, axle box etc for load-cell fitment, instrumentation etc.

The oscillation trial is carried out either on ‘Main line’ for operation at less than 110 kmph on 52 kg rail or on 90R rail track and/or on ‘High-speed line’ for operation at 110 kmph or above and up to 140 kmph on track maintained to C&M1-Vol.1 standard. The criteria for assessment is detailed in the ‘Third report of standing criteria committee’ issued in January’2000 and amended on 10.07.2000.

Quality of Ride:

Human sensation of comfort is dependent on displacement, acceleration and the rate of change of acceleration. In other words, the product of displacement, acceleration and the rate of change of acceleration could be used as a measure of discomfort during travel.

The term Ride quality means that the vehicle itself is to be judged. Ride comfort means that the vehicle is to be assessed according to the effect of mechanical vibrations on people in the vehicle.

The following classification of RI with reference to subjective appreciation is usually adopted on Sperling’s scale as per ORE report no. 8 of C-116:

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RIDE QUALITY

Ride Index Appreciation

1 very good

2 good3 satisfactory

4 accepted for running

4.5 not accepted for running

5 dangerous

RIDE COMFORT

Ride Index Appreciation

1 just noticeable

2 clearly noticeable

2.5 more pronounced but not unpleasant

3 strong, irregular but still tolerable

3.25 very irregular

3.5 extremely irregular, unpleasant, annoying, prolonged exposure intolerable

4 extremely unpleasant, prolonged exposure harmful

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In the analogue or chart recorder method, the correction factor for frequencies below 0.5 Hz are not relevant since the average common frequency is always above 0.5 Hz. In DAS method, since the frequency of every half wave has to be considered individually, some of the half waves may have frequencies less than 0.5 Hz for which a correction factor of 0 has been assigned. This is because frequencies below 0.5 Hz have very low energy levels and do not affect the ride comfort.

The accelerometers are placed on the floor level of the vehicle near the center pivot for measuring the acceleration and calculating RI.

Stability & Dynamic Forces:

Vertical and lateral forces are developed between the rail and the wheel as a result of dynamic interplay of track and vehicle characteristics. It is important to understand these forces because of their role in vehicle stability and track stresses. Generally these forces can be classified into three categories, namely, static forces, quasi-static forces and dynamic forces.

Static forces arise due to static wheel load applied on the rail. Quasi-static forces are developed due to one or several factors, which are independent of the parasitic oscillations of the vehicle and do not vary in a periodical manner. Centrifugal forces caused by cant excess or deficiency, curving action on points and crossings and forces due to cross winds fall in this category.

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Dynamic forces are caused by track geometry and stiffness irregularities, discontinuities like rail joints and crossings, wheel set hunting and vehicle defects like wheel flats. Dynamic forces are the most significant ones in the study of vehicle stability and rail stresses and are also the most difficult to mathematically determine or to experimentally measure.

According to Esveld, the frequency ranges for the vertical dynamic forces are 0-20 Hz for sprung mass, 20-125 Hz for un-sprung mass and 0-2000 Hz for corrugations, welds and wheel flats. The vertical forces in the lower frequency range are produced due to vehicle response to changes in the vertical track geometry like unevenness and twist whereas forces in the higher frequency range are caused by discontinuities like rail joints, crossings, rail and wheel surface irregularities. A wheel flat produces high frequency peaks at regular intervals, which is easily distinguishable from other surface irregularities.

The net lateral forces acting on the track by the wheel set can lead to the distortion of track laterally, causing derailment. In other words, this force is a measure of lateral strength of the track. This force is equal to the lateral force at axle box level as a result of reaction of the wheel set with the vehicle body/bogie. This force, usually denoted by the symbol Hy, can be measured with the help of a load-cell placed between the journal face and the axle box cover or the bogie frame and the axle box.

Derailment Coefficient:

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Derailment can happen when the values of lateral and vertical forces acting at the rail-wheel contact point assume a critical combination leading to mounting of the flange on the rail. This phenomenon is known as derailment by flange mounting.The fundamental forces that are to be considered in this context are the lateral forces as a result of flange reaction; tread friction and lateral creep on the rail and the dynamic vertical load of the wheel at that instant. All the theories that have been evolved to explain the phenomena of derailment have tried to establish a suitable ratio between the instantaneous values of lateral force and vertical force at the rail-wheel contact point beyond which derailment may occur. Mr J.Nadal, Chief Mechanical Engineer of French State Railway propounded the earliest of these theories of derailment by wheel flange mounting the rail in 1908. Provided that the vehicle does not overturn and that the outer rail is capable of sustaining the lateral load, the limiting lateral force, which may be applied to a wheel, is determined by the possibility of the flange climbing the rail, thus producing derailment. As the vertical load carried by the wheel opposes this action, it is necessary to determine the relationship between the limiting horizontal force and the vertical load coming on the wheel. Consider a flanged wheel supporting a load Q and subjected to a lateral thrust Y passing round a curve. It is seen that the point of contact between the flange and the rail will be slightly ahead of the wheel center line so that at the point of contact the flange will have a small movement downwards, producing a frictional reaction Y in an almost vertical direction.

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Wheel

Y

Rail

The flange will begin to climb the rail as soon as the frictional force µY exceeds the load Q. Let the flange make contact with the rail at some angle Ө and the lateral force Y produce a reaction QR from the rail at the point of contact.

Q

Wheel

Rail

Y

QR

QR

Where, Y and Q are the instantaneous values of the lateral and vertical forces at the rail-wheel contact point, is the angle of flange with horizontal plane and is the coefficient of static friction between wheel tread and rail.

It can be seen from Nadal’s formula that for =0.27 and =600, Y/Q =0.997 or 1. This is the limiting value beyond which the wheel flange will tend to mount on the rail table. The other question is that of the duration for which this ratio can exceed the value of 1. It is well known that derailment by flange mounting is not an instantaneous, but a gradual process. In Japanese Railways, the

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limiting value of Y/Q is taken as 0.04/t if t is less than 1/20 seconds and 0.8 if exceeds 1/20 seconds.

Instrumentation:

The instrumentation is done as per test scheme. Normally, instrumentation used for recording data is transducers as input device, signal conditioners as processing device and chart recorders and/or computerised data acquisition system as output device. Power supply unit is used to provide power supply to signal conditioners and recorders and excitation to passive transducers.Transducers are used to measure acceleration, deflection and force. Signal picked up from transducer is fed into signal conditioner for processing. The processed output from signal conditioner can be recorded on chart recorder and/or acquired on computer (PC or laptop) through data acquisition cards. Transducers normally used are passive types either resistive or inductive. Transducer used for measurement of acceleration in x, y and z directions is also called accelerometer and can be either ‘strain gage type’ or ‘piezo electric’. Transducer used for measurement of deflection of spring, bolster, bogie movement etc can be either LVDT, i.e., linear voltage differential transformer or string-pot. Transducer used for measurement of force or load at axle box level is normally a load-cell. Measuring wheel measures lateral and vertical forces at rail wheel level. Transducers are excited either by 5V rms 2.5 kHz AC or DC voltage to provide output signal.One unit of signal conditioner is required for processing a ‘channel’ or input signal from a transducer. The function of a signal conditioner is to make signal suitable for input to a DAS and can be divided into six broad activities. The first activity is application of excitation potential or power. The second activity is balancing. A Bridge

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Balancing Device or ‘Balancing unit’ can be either a potentiometer-comprising resistor and capacitor knobs or an auto balancing push button. The balancing unit is used to balance the input signal to a datum or reference line called null point. This is done under no load condition. The third activity is demodulation. Rectifier or Demodulation unit cuts off the carrier frequency and allows only the output signal from the transducer. This is required only in case of AC voltage excitation (about 2.5 kHz) of transducer. The fourth activity is filtering. A Filter unit has different filter setting conditions. The ‘low-pass’ filter knob can be selected to a desired level of filtering. Thus, only frequencies lower than the selected frequency is allowed to pass through and higher frequencies are cut off. The fifth activity is amplification. Amplifier unit steps up the input signal, in the order of mV, to a desired level. The sixth activity is attenuation or increasing the gain. Attenuation unit or gain has a knob with different gain settings and is used to amplify the signal as necessary. Load cell assembly is used for recording lateral forces at axle box level. Load cell of strut type is manufactured in-house suiting to the axle box arrangement with range of measurement from 0 to 10t compressive load only. Load cell is of full bridge resistance type and calibrated with excitation voltage from 5 to 10V AC and under pre-calibrated hydraulic jack. Its output is about 90 mV/V/tonnes. A load cell calibration chart is prepared with load in tonnes on x-axis and mV output on y-axis. The excitation voltage used during calibration is mentioned in the chart. Care should be taken to use the same excitation voltage during trial.Measuring wheel is used for measuring vertical and lateral forces at rail wheel level. FEM analysis of wheel conforming to s-shape web profile is carried out to determine the strain gage locations sensitive to vertical and lateral force. The strain gage locations used for measurement of lateral force are having minimal effect of vertical wheel load and similarly, strain gages for vertical wheel load are having minimal influence of lateral load. The cross talk between

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vertical and lateral forces is kept to the barest minimum while selecting the locations. Wheatstone bridges are formed for vertical and lateral force measurement channels. Measuring wheel supplied by Swede Rail has two vertical and one lateral load sensing bridges per wheel. Sixteen strain gage locations have been selected for vertical bridge with two gages per arm and twelve locations for lateral bridge with three gages per arm. This means that in one revolution of the wheel two vertical and one lateral value would be obtained. Measuring wheel supplied by AAR has one position channel in addition to above, which indicates the rail wheel contact point. Output of channels is taken from slip-ring device fitted on axle end cap. AAR measuring wheel-set has slip-ring device on both ends of the axle. Swede Rail measuring wheel-set has slip-ring device on one end of the axle. Output signal lead from left wheel to right wheel is transferred through a hole drilled in the axle. This has been done to save the cost of slip-ring device. All measuring, signal-conditioning and recording instruments are issued by the Electronics Lab duly calibrated as per ISO 9000 norms. Load cells are calibrated and issued by Fatigue Testing Laboratory. In addition, output calibration of all transducers like accelerometer, LVDT, string pot, load cell etc should be done daily before the trial run. Instruments defective or due calibration should be returned to Electronics laboratory and good/calibrated instruments are to be drawn by the unit.Instrumentation set up is made as explained in sketch below. Six channels can be connected in a signal conditioner.

AccelerometerLVDT Load cell String pot

Ch 1 Ch 2 Ch 3 Ch 4 Ch5 Ch 6

Ch1 Ch2 Ch3 Ch4 Ch5 Ch6

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~ 230V Signal conditioner

Flick from Loco Cab

Ch1 Ch2 Ch3 Ch4 Ch5 Ch6

Chart recorder~ 230V

A parallel path from signal conditioner is connected to an interface, if recording is done both on chart recorder and DAS. Otherwise, output from signal conditioner is directly connected to interface through two-core shielded wires for each data channel and properly grounded.

Interface is connected to DAC installed in one of the slots of PC.

Measurement of Load, Stress & Strain:

In a balanced Wheatstone bridge connected with resistors R1, R2, R3 and R4, the electrical output eo is zero. By applying Ohm’s law, we get, R1/R4 = R2/R3……(1).

R1R2

eo

R3 R4

Ev = Excitation Voltage AC or DC

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R1 is an active arm of the bridge if resistor R1 is replaced with a strain gage and bonded on the material, which is under strain. In unbalanced condition of the bridge when active arm resistance is changed by dR1, by applying Kirchhoff’s law, we get, eo= [(R1xR2)/(R1+R2)2]x[dR1/R1] * Ev ……. (2). Gage factor (GF) = [dR/R]/[dl/l], where, l is length of gage filament. Strain (e) = dl/l and thus, dR/R = GF x e……..…. (3).Substituting dR/R and R1=R2=R in equation (2), we get, eo= (Ev*GF*e)/4 ……. (4).

Resistance of most conductor changes with temperature. Also, thermal coefficient of expansion of the strain gage filament is different from that of the structure to which it is bonded. Thus, strain gage is subjected to false strain indications with temperature. The temperature compensation is accomplished by a second dummy strain gage on an unstrained piece of the same metal as that to which the active gage is bonded. This dummy gage is either R2 or R4 so that ratio (1) is undisturbed, i.e., [R1+dR1]/R4 = [R2+dR2]/R3. In case of four active arms of the bridge, by applying Kirchhoff’s law, we geteo=[(R1xR2)/(R1+R2)2]*[dR1/R1-dR2/R2+dR3/R3-dR4/R4]*Ev …. (5).Substituting R1=R2=R3=R4=R in equation (5),eo= (Ev*GF*e*n)/4 ……. (6)Where n is the number of active arms. In this case, R2 and R4 accomplish the temperature compensation of R1 and R3.

P

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R1 R1P

P

R2 R3

Fig A Fig B

In Fig A above, R1 is tensile & R2 is compressive strain. Temperature compensation gets cancelled because of same effect on R1 & R2. However, in Fig B above, R1 & R3 are compressive strain. Temp compensation is doubled and therefore, dummy gages R2 & R4 are to be used for temperature compensation. It is worthwhile to note that temperature effect of a gage bonded on curved surface is more than flat surface.

Measurement of lateral force is done by load-cell. R1&R3 are bonded on the load-cell in y-axis for measuring compressive strain and R2&R4 are bonded in z-axis for temperature compensation (also have Poisson’s strain). ‘Load (tonnes) vs output (mV)’ calibration chart is prepared in laboratory by subjecting the load-cell to known loads. This chart is used during trial to calculate lateral force where output measured is converted to load (lateral force). It is important to use the same excitation voltage during trial that has been used during calibration. This is simply because electrical output is directly proportional to excitation voltage. If a different excitation voltage is used during trial, then a correction factor of (Echart/Etrial) should be multiplied to the electrical output to read the chart. The excitation voltage should also be steady.

P

z

R2 R1x

y

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R1 is under tensile strain and R2 is under Poisson strain equivalent to -(x/E). Poisson’s ratio () varies from 0.25 to 0.35 for most metals.eX = X/E - Y/E - Z/EeY = Y/E - X/E - Z/EeZ = Z/E - Y/E - X/E

If enough strain gages are mounted adjacent to or overlapping each other to obtain the principal strains in an area the resulting configuration is termed a strain rosette.

3In ‘Rectangular Rosette’, 21 = 00, 2 = 450 and 3 = 900

Maximum normal stress is, 1 max =E/2*[(e1+e3)/(1-)+1/(1+){(e1-e3)2+(2e2-(e1+e3)2)}0.5]Minimum normal stress is,min =E/2*[(e1+e3)/(1-)- /(1+){(e1-e3)2+(2e2-(e1+e3)2)}0.5]Maximum shearing stress is, max =E/2(1+)*{(e1-e3)2+(2e2-(e1+e3)2)}0.5 Angle from gage 1 axis (x-axis) to maximum normal stress is, P = 0.5*tan-1[{2e2-(e1+e3)}/(e1-e3)] 2

Similarly for ‘Two-gage Rosette’, max = E/(1-) [e1+e2] 1 min = E/(1-) [e2+e1]max = E/2(1+) [e1-e2] and P = 0

If RSh is shunted across R1, then, Req = (R x RSh) / (R + RSh) or change in resistance, dR = R - Req = R2/(R + RSh). Substituting dR in equation (3), e0 = R/[GF(R+RSh)] ………(7)

If R1=R2=R3=R4=R= 350 ohm with GF=2.13 and all are active arms of the bridge, strain e = 350/[2.13x240350] = 0.00068 when a

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240 k-ohm resistance is shunted across arm R1. Under no-load condition with 5V DC excitation voltage, eo = 5x2.13x 0.00068/4 = 0.00182 V or 1.82 mV.

In ‘Squeeze Test’ of coach shell or vehicle under-frame, stresses at critical locations are determined. The shell or under-frame is subjected to extreme compressive (buffing gear), tensile (CBC) and vertical loading (gross weight) conditions. The critical locations are identified by FEM analysis. Strain gage, R1 is bonded on the location where stress is to be measured. Strain gage, R2 is bonded on an unstrained location on the shell or under-frame for temperature compensation. Resistor R3 & R4 are provided in the Apex Unit.

If R1 = R2 = R3 = R4 = R = 350+1 ohm with GF=2.13 and gage length of 10 mm, strain e = 350 / [2.13 x 360350] = 0.000456 when a 360 k-ohm resistance is shunted across arm R1. Under no-load condition with 5V DC excitation voltage, eo = 5x2.13 x 0.000456/4 = 0.0012 V or 1.2 mV. If E of the material is 2.10x10-4 kg/mm2, then, stress = e*E = 4.56x2.1 = 9.58 kg/mm2. Thus, 1.2 mV corresponds 9.58 kg/mm2 or 1 mV is equal to 7.98 kg/mm2. Electrical output of the bridge is measured under different load conditions and is used directly for calculation of stress.

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CONCLUSION

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REFERENCES

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THANK YOU …..