research and development of a new method for wirelessly ... · pdf fileresearch and...

AREMA 2008 Technical Paper

Research and Development of a New Method for Wirelessly Interrogating the Stress Free Temperature of Continuously Welded Rail

Nigel PetersCN Rail

[email protected]

Richard BurchillIDERS

100-137 Innovation Dr.Winnipeg, MB, Canada

R3T 6B6Tel: (204) 779 5400 Fax: (204) 779 5444

[email protected]

David FletcherIDERS


R3T 6B6Tel: (204) 779 5400 Fax: (204) 779 5444

[email protected]

Bradley BrownIDERS


R3T 6B6Tel: (204) 779 5400 Fax: (204) 779 5444

[email protected]

Randy WallackCN Rail

[email protected]

Word countAbstract = 231 + Illustrations = 12 * 250 (3000) + Body= 4293

mailto:[email protected]

mailto:[email protected]

Peters N., Burchill R., Fletcher D., Brown B., Wallack R. 1

ABSTRACT

The management of the neutral temperature on CWR (Continuous Welded Rail) is a significant

issue facing railways. Quantitative measurements are critical to managing systems as complex as

track. The creation of an affordable, reliable and practical system for measuring and monitoring

the SFT (Stress Free Temperature) of CWR on an entire network has proved elusive. An ideal

tool must be low-cost, accurate, rugged, robust, require no service or parts, simple, quick to

install and interrogated wirelessly. Such a system manifested as a rail-mountable sensor could be

used to quantify track work with certainty as well as detect emergent problems caused by track

and surfacing work, location geometry, tonnage and temperature affects.

CN (Canadian National) and Iders Inc. collaborated on a process to identify how and where the

information from an SFT measurement and monitoring system could be used most effectively.

Once the uses for the SFT information were identified, requirements and specifications were

developed to determine how the system would provide the information. The the main

requirement was a plug mounted, self powered, wireless strain sensor.

This paper presents the invention of a new type of self powered wireless strain sensor,

engineered from the ground up, for use on CWR to monitor the SFT. It details the collaborative

process between CN and Iders Inc. through specification, R&D, design validation testing and

large scale deployment for production use.


INTRODUCTION

For decades the search for tools and technologies used to manage rail neutral temperature or SFT

(Stress Free Temperature) in CWR (Continuous Welded Rail) has been an outstanding issue. The

list of technologies, requirements, capital expended (both human and monetary) in their creation

is legion. Still, there is no ubiquitous adoption of a technology or system that meets all the

requirements. With few a exceptions the past work seems to be a solution in search of a problem.

The CN/Iders Inc. solution recast the problem in terms of how knowledge of the SFT could be

used by CN (Canadian National).

This change in focus allowed CN and Iders to identify where a solution could be best applied.

Although the industry identified many general requirements for an SFT measuring and

monitoring system (1, 2, 3, 4). CN provided much needed specific direction on the goals and

uses for such a system.

Initial requirements dealt primarily with the integrity of existing infrastructure, safety as well as

the constraints posed by existing rail equipment and processes. The goals that CN and Iders

identified for the SFT measurement and monitoring system aligned with many of the

requirements outlined in the literature. Therefore, solutions were developed using some of the

work carried out by the FRA, RSSB and TTCI.

An evaluation of existing SFT measurement and monitoring systems, as well as other

technologies that offered possible integration into a solution, was carried out using Iders'


experience with the integration of technologies in the field of SHM (Structural Health

Monitoring) and its close connection to local and international researchers..

This paper covers the collaborative effort by CN and Iders in the design and development of a

novel solution that will allow CN to take a proactive stance in the management of its

infrastructure. The system called SFTPro incorporates a novel wireless strain gauge, man

portable and mobile interrogators as well as a set of attachment systems.

BACKGROUND

The rail industry has recognized that effective management of the SFT in CWR is essential for

safe and profitable operation. Controlling the effects of longitudinal thermal forces in CWR is

necessarily a compromise between compressive forces, that can lead to buckling, and tensile

forces, that have been shown to accelerate defect growth and cause rail and welds to fracture.

Unfortunately the current tools for managing the SFT are generally procedural as opposed to

deterministic and correction is generally reactive rather than proactive.

The Stress Free Temperature (SFT, TN, RNT or NRT) is the rail temperature at which the net

longitudinal force in the rail is zero. It is often associated with the Preferred Rail Laying

Temperature (PRLT or NRLT) and has a direct relationship to the force (P) in the rail:

P=EAT R−T N Equation (1)


Equation (1) may be used to calculate the force ( P ) produced in the rail by the temperature

difference between ( TR ) (temperature of the rail) and ( TN ) (Stress Free Temperature). The

assumptions in the above are that the rail is perfectly constrained and the SFT is known. In

practice the SFT is not known to any great certainty and is assumed to be the PRLT. In addition

studies have shown that the SFT varies cyclically (breaths) and tends to trend downward (5).

Therefore, the calculation of the thermal force from equation (1) can become very complicated

and contains large errors and gross assumptions.

The challenge is to control thermal forces inspite of uncertainty in the SFT in CWR. The SFT of

new rail is close to the PRLT only when all the procedures for laying and destressing new rail are

carried out correctly. Assuring that the procedures produced the required results is not possible

without undoing some of the work. So right from the beginning there is some uncertainty as to

whether the SFT = PRLT. From this point on constant change of the SFT in CWR is the

challenge faced when trying to control the thermal forces.

These changes are driven by factors in two general categories; Rail Kinematics (Creep,

Breathing, Settlement etc.) and Rail Maintenance (Installation, realignment, destressing, defect

repair etc.). Uncertainty in the SFT is caused by repair of rail defects and broken rails which

results in a distribution of SFT across the track system. The width of this distribution can be

approximated by the ratio of breaks to buckles. In an effort to keep the low end of the

distribution from creating an unacceptable buckling cost the industry must use procedures to

target the SFT at the top end of the acceptable PRLT range. See Illustration (1)


As the distribution is pushed towards a higher SFT (Towards the right in Illustration 1) the cost

of tensile induced defects and breaks increase. This can been seen across the industry over the

last two decades as the PRLT has increased 10°F to 20°F in many regions. Due to uncertainty in

the width of the distribution, the risk of buckling cannot eliminated.

GOAL IDENTIFICATION

CN installs 10 000 plugs per year to fix defects and broken rails in western Canada. This is a

major cost and contributor to uncertainty in the width of the SFT distribution. CN and Iders

identified that an SFT measurement and monitoring solution that provides feedback on the SFT

of defect repair would have the greatest impact on helping to quantify the SFT distribution. In

addition, across Canada, 4,000 IJ's (Insulated joints) are installed or replaced each year, offering

Illustration 1: Uncontrolled SFT Distribution


a similar opportunity to provide surety in the repair and in the management of SFT.

Even if only half of the defects and IJ's were installed with a SFT measurement and monitoring

solution, within five years CN would have a density of between one and two monitored locations

per mile on every rail.

CN 's second goal was to reduce the width of the SFT distribution. See Illustration (2)

This is possible because of the SFT measurement and monitoring at places where the greatest

uncertainty currently exists. Commencement of the proactive phase allows changes to procedures

and repairs before a problem occurs.

Illustration 2: Narrowed SFT distribution after control


Finally the possibility exists to reduce the PRLT. See Illustration (3)

A narrower distribution reduces the PRLT while realizing an acceptable buckling risk. Usually,

the reduced PRLT and the general reduction in the overall SFT distribution leads to reduced

fatigue failures and fewer defects overall.

As a consequence of better control and understanding of the SFT in their system, CN hopes to

achieve the following:

Measure and monitor on a large scale, initially 4,000 to 8,000 locations per. year in

western Canada.

Concentrate the measurement and monitoring effort on defect plugs, IJ's and fixed points.

Narrow the width of the SFT distribution.

Illustration 3: PRLT shifted after SFT distribution narrowed


Downward shift of the PRLT to reduce tension defects and breaks.

Evaluation of current track standards and processes.

Increase precision in de-stressing gang results as it becomes possible to measure the true

SFT without taking up or cutting the rail.

Reduce need for temperature based Slow Orders, or at least limit them to known areas of

concern.

Verify that tamping eliminates existing stress problems and does not create new ones.

Equalize SFT on both rails in a curve to reduce gauge variations and rail wear.

Monitor the quality of anchors and ballast resistance (running and breathing).

CN and Iders determined that the SFT measurment and monitoring system must:

Utilize sensors that do not require any maintenance or power.

Reduce the amount of equipment necessary for installation and calibration. Calibrating

sensors on the plug or IJ before transportation to the installation location.

Eliminate the need for full time (live) monitoring. Monitoring will be carried out as part of

regular track inspection with equipment mounted interrogators.

Must use wireless interrogation, 6in. (150mm) distance for hand held, 12in (300mm) and

20 mi/hr (32 km/hr) for mobile.

Maintain a 1-n interrogator to monitored location relationship. Move as much complexity

as possible to the interrogator.

Employ sensors impervious to either Flash Butt Welding or Thermite Welding

Do not rely on a central data base for calibration information or retrieval of historical data.


Any interrogator must provide accurate SFT information at any location at any time.

Track a minimum of 2000 measurement records per monitored location. (Readings once

per day for 5 years or twice a week for 20 years).

Use railroad approved attachment systems.

Function in temperatures from -40°F to +160°F (-40°C to +70°C)

Survive in temperatures from -55°F to +175°F (-50°C to +80°C)

Do not interfere with modern track equipment (tampers, threaders spikers etc.)

Mount to the gauge side of the rail.

Provide ±5°F (±3°C) SFT life time accuracy

Provide ±1°F (±0.6°C) SFT resolution.

Not be substantially affected by residual stress.

SFT MEASUREMENT AND MONITORING SYSTEM EVALUATION

Of the many SFT measurement and monitoring systems identified in the literature (1, 3, 4) only

three types of systems; Load Deflection, Stress Measurement and Strain Measurement, are

currently use. Iders evaluated them against the goals and requirements set out by CN.

Load Deflection Systems

The only example of an Load Deflection system in wide spread use is the VERSE. This system

requires that the rail is unclipped and can only be used when the rail temperature is below the

lower acceptable limit for the SFT. Specifically the rail must be in tension. Despite this limitation

the VERSE is a recognized standard against which the accuracy of other systems are measured


(1). It requires no site specific calibration and can determine the SFT of any rail type if the

profile, metallurgy, state of wear and temperatures are known. It has a claimed mean error of

2.5°F (1.4°C) and a standard deviation of 1.8°F (1°C). Because it integrates the stress over 100ft

(30m) the measurements are not affected by the residual stress in the rail.

CN uses several VERSE to verify contract work and to inspect identified trouble spots. VERSE

works well for this purpose but, has limit use as a monitoring tool because of the track time

necessary for the measurement and the temperature limitations. In addition the measurement is

one time only so is not consistent with the goal of continued monitoring as part of a proactive

approach.

Stress Measurement Systems

MAPS-SFT uses the magnetic properties of steel to measure the absolute biaxial stress. The rail

remains in situ during the measurement requiring no track time as long as there is right-of-way

access to the track. For absolute measurements MAPS-SFT needs empirical data from sample

rail to develop V/L residual stress curves, possibly for each profile and metallurgy. It is accurate

to 1,450 lbf/in.2 or ±7.2°F (±10 Mpa or ±4°C) with appropriate V/L residual stress curves (6).

RAILSCAN uses Magnetic Barkhausen Noise (MBN) to measure the absolute stress. The rail

remains in situ during the measurement requiring no track time as long as there is right-of-way

access to the track. For absolute measurements RAILSCAN needs empirical data from sample

rail to develop temperature/stress calibration curves, possibly for each profile and metallurgy. It


is accurate to ±5.4°F (±3°C) with appropriate calibration curves (7). Surface conditions of the

rail may affect the accuracy of the measurements.

Management of data for V/L residual stress curves (MAPS-SFT) or temperature/stress

calibration curve (RAILSCAN), possibly for each specific steel and rail profile, does not meet

CN's goal of using any interrogator at any location. An accurate measurement would depend on

the operator knowing which curve to use and having access to all the curves. In addition any

historical data would only be available it all interrogators had a copy of every measurement at

every location.

Strain Measurement Systems

Strain based SFT systems use electrical strain gauges to measure the strain in the rail. The strain

gauge must be attached to the rail and calibrated at a known strain and temperature to provide

absolute measurement. All of the current strain based systems store the calibration data as well as

the measurements. Thus any interrogator can provide an accurate measurement and display the

historical sensor data. The calibration of the sensor to the rail and the installation of the rail are

decoupled because the calibration is rail specific and not site specific. This makes it possible for

a small number of calibration crews to supply a much larger number of installation crews. This

fits well with the CN's goal of using plugs at defect locations and replacement IJ's to monitor and

verify the SFT. In addition the strain measurement system is not affected by the type of rail

profile or the amount of wear as can be seen in the following development.


P=EAT R−T N Equation (1)

Where: ( P ) is the force; ( E ) is Young's Modulus; ( A ) is the area; ( α ) is the coefficient of

thermal expansion; ( TR ) is the current or working temperature and ( TN ) is the SFT. The sign

convention is such that a positive or compressive force is produced when ( TR ) is greater than

( TN ).

Given that stress = PA

, strain =LR−LN

LR

and Young's Modulus E=

Where: ( LR ) is the current or working length and ( LN ) is stress free length. The sign convention

is such that strain is positive or compressive when ( LR ) is less than ( LN ).

Substituting ...

=T R−T N Equation (2)

Thus the strain in perfectly constrained rail is directly proportional to the change in the

temperature. Conversely with ( TR ) and ( LR ) fixed (calibrated) under known strain, equation

(2) can be rearranged to solve for ( TN ).

T N=T R−/ or T N=T R−LR−LN

LR

1 Equation (3)

As can been seen from equation (3) SFT is directly proportional to strain and is not directly

related to the rail profile or amount of wear.

SFT STRAIN SENSOR EVALUATION

The strain based SFT measurement and monitoring system was identified as the best fit for CN's


goals. Iders used the experience gained in developing and integrating strain base systems for

SHM to investigate three types of strain gauges. They were evaluated by assessing the skill

needed to attach them to the rail, the complexity of the interrogation equipment and if a suitable

wireless interrogation system existed.

Fiber Bragg Grating

The first were FBG (Fiber Bragg Grating) strain sensors. The “Gold Standard” in strain gauges.

These gauges are very accurate (are self calibrating against NIST standard references), very

stable (do not creep or corrode) and are immune to electrical interference. The gauge is made

from a thin optical fiber with a diffraction grating etched in it. This grating reflects a specific

frequency of light based on the strain across the grating. As the fiber is stretched or compressed

the frequency of light it reflects changes. An FBG strain gauge is also very fragile before

attachment and requires a laser light source that must travel through the fiber from the wayside.

These gauges work well for large civil structures like bridges and nuclear reactors but are not

suited to SFT measurement.

Electrical Strain Gauge

The second was an ESG (Electrical Strain Gauge) sensor. These are the type of gauges used in all

the strain based SFT systems evaluated. ESG strain gauges are a mature technology and well

understood in the mechanical and civil fields of engineering. Once properly attached to the rail,

calibrated and given appropriate environmental and electrical protection they provide an

excellent measure of the strain in the rail.


Proper attachment of an ESG to the rail requires skill, attention to detail and affects the initial

accuracy and long term integrity of ESG sensors. ESG sensors also require a source of power to

excite the strain gauge and for the electronics necessary to measure the micro volt changes across

the gauge. All current strain base SFT measurement systems use either batteries or run power and

communication lines from the wayside to the sensor. Though the ESG is a mature and well

understood sensor element Iders decided that the attachment and power requirements were too

great a compromise.

Wireless Strain Gauge

The third was a wireless strain gauge (8) developed by Iders in partnership with the University of

Manitoba. This strain sensor is an RF (Radio

Frequency) resonator that resonates at its natural

electrical frequency when excited by high frequency

radio energy (Similar to radar where a burst of energy

is transmitted at an object and the “signature” or

frequency of the returned signal is a characteristic of

that object). See Illustration (4) When the sensor is

compressed or stretched the natural electrical

frequency it resonates at changes. Unlike the FBG or

the ESG this sensor requires no power of it's own, it

is excited passively by the radio energy used to

interrogate it. It is robust in construction and can use attachment methods not suitable for the

Illustration 4: Wireless strain gauge


other strain gauges.

The resonator is first mounted to the rail and

calibrated at a known strain or SFT. See

Illustration (5)

As the stress free temperature rises, the rail

and sensor stretch. This change in

dimension produces a drop in sensor

resonant frequency which is proportional to

the change in strain. See Illustration (6)

As the stress free temperature drops, the rail

and sensor compress. This change in

dimension produces an increase in sensor

resonant frequency which is proportional to

the change in strain. See Illustration (7)

The resonant frequency is inversely related to the length of the resonator. So the sign convention

in equation (3) is change to account for the inversion.

T N=T R−f N− f R

f R

1 Equation (4)

Illustration 5: Calibrated sensor

Illustration 6: Sensor in tension

Illustration 7: Sensor in compression


Where ( TR ) and ( fR ) are fixed at a known strain and ( fN ) is the current frequency.

Iders invetigated if the range and function of the wireless strain gauge was appropriate for a

strained based SFT measurement and monitoring system at the Industrial Technology Centre

(http://www.itc.mb.ca/) in Winnipeg Manitoba. Sample sensors were pulled to failure in an

Instron tensile tester to ensure that the elastic range of the sensor was much greater than the rail.

The results showed the sensor had an elastic range greater than .040in. (1mm) over a gauge

length of 3in (75mm). This was significantly more than the maximum normal displacement of

the rail over the same gauge length. See Illustration (8)

Illustration 8: Sensor tensile test


The same test was used to determine the reaction loads of the sensor on the rail for a given rail

displacement. Within the elastic range of the sensor the force need to stretch the sensor .040in.

(1mm) was less than 1200lbf (5.3kN).

Other samples were cycled in tension through 50% of their elastic range to ensure that the

sensors did not creep. The results showed the resonator always returned to the original length.

The results of testing at ITC showed that the wireless strain gauge was a viable option to an ESG

in a strain based SFT measurement and monitoring system.

SFT WIRLESS STRAIN SENSOR DEVELOPMENT

Data Storage

To meet the requirement that the sensor store all

the information necessary for interrogation plus an

additional 2000 measurement records. An

information storage and retrieval system that

required no power source was needed. The

obvious solution was RFID (Radio Frequency

Identification). RFID is a standard method for

storing and transmitting data without the need for a

power source on one end of the transaction. It is Illustration 9: RFID Communication


used extensively to track rolling stock and for access and inventory control. The energy from the

radio communication signal (different from the frequency used to excite the strain gauge) is used

to power the storage section on the sensor. See Illustration (9) The storage of calibration and

measurements in the sensor means any interrogator can read any sensor and provide a historical

view of the SFT. The combination of the wireless strain gauge and the RFID storage system is

called the SFTPro20 sensor.

Attachment

Attachment systems were evaluated on several factors: acceptance by CN, rigidity, creep,

practicality and cost. The systems that were acceptable to CN were; mechanical attachments

mounted through the rail, structural adhesives and some signal bonding methods.

Mechanical

Mechanical attachments were the preferred method of attachment for field installation because

they could be applied in most temperature or weather conditions. With proper installation they

provide very rigid attachments that will not creep or change through the expected 10-year service

life of the sensor. Drilling signal bond and joint bar holes in rail is already done in all railways so

equipment and processes were familiar.

Mechanical signal bonds, structural rivets and zero clearance fasteners were all evaluated. All of

the systems had similar torque, pullout and shear resistance. In most cases these forces were an

order of magnitude greater than the 1200lbf (5.3kN) reaction forces produced by the sensor/rail

combination.


The system that performed the best in all categories was the zero clearance fastening system.

Structural Adhesives

Structural adhesives were evaluated as a less intrusive system for attaching sensors. Structural

adhesives are currently used in many other applications with excellent results, including the

attachment of strain gauges. Structural Acrylic, Structural Urethane, Epoxy and CA

(Cyanoacrylate) were all assessed for shock and impact resistance, adhesion to steel, resistance

to weathering, fixturing and application. Only the structural acrylic adhesives provided the

combination of properties necessary for attaching the sensors to the rail.

The shear strength of the adhesives was tested at ITC. Several samples were pulled to failure. In

most cases the failure strength was a factor of four greater than the reaction loads of the sensor.

In two cases the metal test tickets failed before the adhesive.

The two component and two step structural acrylic adhesives were easy to apply. The clamping

force for both was 2lbf/in.2 and they were available in formulations that reached working

strength in 1 to 2 hours. They are limited to installations when RH is below 90% and the

temperature is above 50°F (10°C). The limitations of the adhesives restrict their use to

attachments made under controlled conditions.

Pin Brazing

Originally developed as an attachment point for cathodic protection it is used extensively for


signal attachments. It was evaluated only as a possible attachment solution through shear load

and corrosion tests. The results were promising and further study is on going.

Attachment Validation

The two attachment systems that were identified in the evaluation process were used to validate

the function of both the sensors and the attachments. Sample sensors were attached to 16in.

(400mm) sections of 115lb, 132lb and 136lb rail using the mechanical and adhesive techniques.

These sections of rail were instrumented with thermocouples and electrical strain gauges to

evaluate the accuracy of a mounted sensor. A 600 ton (5,300 kN) load frame at the University of

Manitoba Structures Lab was used to test the frequency response of the wireless strain sensors to

Illustration 10: Sample of compression test data

-30

-20

-10

0

10

20

30

40

50 -150

0

150

300

450

600

750

900

1050

1200

1350

1500

Test # 4, Sample # 6, May 31, 2007, 12:12 to 12:27

Profile 115 lb, E=30,000,000 lbf/in 2̂, X-sec=11.25 in 2̂, Temp=21.9°C, fr=2459031200 kHz

Sensor Attachment: 2 Part Structural Acrylic Adhesive

LOAD kNRSG SFTESG SFT

TIME

SFT°C


compression. The load on the samples was increased in 33,750 lbf (150kN) increments and

returned to zero load after each increase. The SFT was calculated using equation (4) with the

resonator data. The results were compared against the ESG data using equation (3). The results

agreed to ±4.5°F (±2.5°C). See Illustration (10) for a sample of the data gathered from the

compression of a sensor mounted using adhesive. The samples that used mechanical attachments

produced similar results.

FIELD TRIALS

Approximately 100 SFTPro20 sensors were installed on CN track across western Canada from

the fall of 2006 until the spring of 2008.

The first installation took place at Calrin on the CN main line west of Winnipeg, Manitoba. The

sensors were used to gather shock and vibration data on the rail. Sensors included a 3 axis 100g

accelerometer, four Fiber Bragg strain gauges, 8 electrical strain gauges, two thermocouples and

four wireless SFTPro20 strain gauges. All of the gauges were shop mounted on a plug that was

Thermite welded into the main line. Sensors at Calrin provided mechanical and environmental

rail data that was not readily anywhere else. The sensors have now logged almost two years of

data covering the effect of flat wheels, large loads, fast trains and temperature changes on

mainline track.

In the fall of 2007 two more sites were added. One on the CN mainline at McGregor, Manitoba

on the Rivers subdivision and one on the CN mainline at Nokomis, Saskatchewan on the


Watrous subdivision. Preproduction SFTPro20 sensors were installed with mechanical

attachments during the relay of 1 mile of track at each location. They provided the first test of the

total SFTPro system including the SFTPro1500 portable interrogator. These installations

provided valuable data on the affects of extreme temperature and weather on the SFTPro system

and on the track See Illustration (11).

Changes were made to the SFTPro system, based on the initial installation and continued data

collection at Watrous and McGregor. These changes facilitated the installation of 60 additional

sensors through the early winter of 2007 and spring of 2008 at temperatures below -22°F

(−30°C).

The largest SFTPro sensor installation and interrogation system deployment will start in August

2008 with the manufacture and release of the production SFTPro20 sensor See Illustration (12),

SFTPro1500 hand held interrogator and SFTPro1700 vehicle mounted interrogator.

Illustration 11: Watrous sample sensor data, first month. Note SFT tracking ambient.

CAL +1 hour

8070

10

45

SFT ( F)o

TEMP ( F)o

+4 hours +8 hours +10 hours +14 days +24 days

All jointsbolted

joints 1 & 2welded

Rail laid &destressed80

45

70

10SFT(°F)

TEMP

(°F)


CONCLUSION

Canadian National and Iders Inc. developed a new Stress Free Temperature measurement and

monitoring system. Their objectives helped focus the specification and requirements for the

SFTPro Wireless strain gauge and interrogation system. The main objective was to create a

proactive system that reduced uncertainty in the SFT of the rail. Objectives were designed to

quantify the current distribution of SFT, narrow the width of the distribution of the SFT and shift

the PRLT to reduce tension related defects without increasing the risk of buckling. In practical

terms the specifications set the parameters for the design of a toolset capable of meeting the

outlined objectives. This toolset involved the creation of a novel wireless strain sensor, that is

efficient, affordable, and easy to install on a very large scale. The end result will be a feedback

system that will permit ongoing monitoring and evaluation of current track maintenance

procedures on a widespread scale.

Illustration 12: SFTPro20 sensor and cover


REFERENCES

1.) Findings from the Investigation of SFT Measurement TechniquesA report produced for Rail Safety & Standards BoardDraft February 2005AEATR-II-2004-020

2.) “Smart” Rail Plug DevelopmentSung H. Lee Program ManagerTrack Research Division, Office of Research and DevelopmentFederal Railroad AdministrationPresented to: Workshop on the Measurement of Longitudinal Stresses in Rail March, 2005

3.) Government of India, Ministry of RailwaysIndian Railways Institute of Civil Engineering, Pune“Comparative Study of Various Methods of Measurement of Stress Free Temperature in CWR Track”June 2006, Ramgopal, Dy.CE/C/CN, A. Ilampooranan, Sr.DEN http://www.iricen.gov.in/projects/623/

4.) LONG WELDED RAILS 1996INDIAN RAILWAYS INSTITUTE OF CIVIL ENGINEERING, PUNEAjit Pandit Senior Professor & Dean

5.) Kish, A., G. Samavedam, & D. Jeong. (1987) The Neutral Temperature Variation ofContinuous Welded Rails, American Railway Engineering Association Bulletin,No. 712, pp. 257-279.

6.) APPLICATION OF THE MAPS STRESS MEASUREMENT TECHNOLOGY IN THE RAIL INDUSTRY, INCLUDING A NEW DEVELOPMENT FOR THE NONDESTRUCTIVEMEASUREMENT OF STRESS-FREE TEMPERATUREPeter Thayer, David Buttle, William Dalzell, Vaughan Thompson, Neil CollettAEA Technology plc.

7.) Non-Destructive Determination of the Stress Free Temperature in CWR tracksGoldschmidt Thermit GmbHInternational Rail Forum, Madrid 2004, Dr. A. Wegner

8.) US Patent 7,347,101 B2Mar. 25, 2008Thomson et al.Measuring Strain In a Structure Using a Sensor Having an Electromagnetic Resonator

http://www.iricen.gov.in/projects/623/

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