I United States Department of Commerce

I AJC31 National Institute of Standards and Technology

NISTIR 3967

Report No. 22

TREAD CRACK DETECTION IN

RAILROAD WHEELS:

AN ULTRASONIC SYSTEM USING EMATS

Raymond E. Schramm

Alfred V. Clark, Jr.

Dragan V. Mitrakovic

Yossef Cohen

Peter J. Schull

Stephen R. Schaps

-QC —

100

. U56

3967

1991

C-2

NISTIR 3967

Report No. 22

TREAD CRACK DETECTION IN

RAILROAD WHEELS:

AN ULTRASONIC SYSTEM USING EMATS

Raymond E. Schramm

Alfred V. Clark, Jr.

Dragan V. Mitrakovic*

Yossef Cohen**

Peter J. Schull***

Stephen R. Schaps

Materials Reliability Division

Materials Science and Engineering Laboratory

National Institute of Standards and Technology

Boulder, Colorado 80303-3328

*NIST Guest Researcher, on leave from the University of Belgrade

**NIST Guest Researcher, on leave from the Nuclear Research Center - Negev, Beer Sheva Israel

***Present address: Dept, of Materials Science, Johns Hopkins Univ., Baltimore, Maryland

May 1991

Prepared for

U.S. Department of Transportation

Federal Railroad Administration

Office of Research and Development

Washington, DC 20590

U.S. DEPARTMENT OF COMMERCE, Robert A. Mosbacher, Secretary

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY, John W. Lyons, Director

CONTENTS

Page

ABSTRACT 1

INTRODUCTION 2

CONTRACT HISTORY 3

WHEEL INSPECTION SYSTEMS: OVERVIEW

Conventional Ultrasonics 4

EMAT Ultrasonics - Germany 5

EMAT Ultrasonics - United States 5

Magnetic 5

References 6

IN -RAIL EMATS

Principles 9

Configuration 11

OPERATIONAL PRINCIPLES

Transducer Package 14

Analog Electronics 18

Digital Electronics 18

Report Station 18

EQUIPMENT INSTALLATION

In- Track EMAT 18

Connections and Cables 21

EXPERIMENTAL RESULTS 23

Laboratory Tests 23

Acoustic Signatures 23

Wheel OK 23

Single Flaw 26

Multiple Flaws 26

Blind Spots 26

Field Tests 27

ELECTRONIC SCHEMATICS

Analog 28

Digital 31

List of Electronic Components 31

SOFTWARE

Operation 47

Program Listings 48

CHECKLIST 60

TROUBLE SHOOTING 60

FUTURE CONSIDERATIONS 61

OTHER POTENTIAL APPLICATIONS 63

ACKNOWLEDGMENTS 63

APPENDIX: PUBLIC NOTICES 64

iii

TREAD CRACK DETECTION IN RAILROAD WHEELS:

AN ULTRASONIC SYSTEM USING EMATS

Raymond E. Schramm, Alfred V. Clark, Jr.,

Dragan V. Mitrakovic"’, * Yossef Cohen,** JL Peter J. Shull, and Stephen R. Schaps

Materials Reliability Division

Materials Science and Engineering Laboratory

National Institute of Standards and Technology

Boulder, Colorado 80303-3328

* NIST Guest Researcher, on leave from the University of Belgrade

** NIST Guest Researcher, on leave from the Nuclear Research Center - Negev, Beer Sheva, Israel *** Present Address: Dept, of Materials Science, Johns Hopkins University,

Baltimore, Maryland

This is report number 22 in a series covering research performed

by the National Institute of Standards and Technology (NIST) for

the Federal Railroad Administration (FRA) . This report covers a

project by the Materials Reliability Division (formerly the

Fracture and Deformation Division) to develop and build an

ultrasonic system to detect crack- type flaws in the tread of

railroad wheels. To achieve fully automatic operation, the sensor

is built into the rail so testing occurs as the train rolls past.

Signal analysis takes place in real time.

The ultrasonic probe is an EMAT (electromagnetic -acoustic

transducer). As configured here, the EMAT has a small footprint,

and, due to its principle of operation, it does not require any

acoustic couplant. The system operates in a pitch- catch mode. A

short burst of Rayleigh (surface) waves travels around the wheel

tread, and an echo indicates a flaw's presence and size. Testing

was performed on both a short track in the NIST laboratory and the

full-scale facilities of the Transportation Test Center (TTC) in

Pueblo, Colorado.

This report documents the design, construction, and testing of the

system. It is also to serve as an operational guide for the equipment

being delivered to the FRA.

Key words: crack; EMAT; nondestructive testing; railroad wheel; rollby inspection; ultrasonic.

1
INTRODUCTION

In this country, most railroad operations now deal with the transportation

of freight in its many forms. Modern needs place ever greater demands on

the elaborate rail network that began developing early last century. Just

one of the important elements in this complex system is the integrity of the

many wheels that bear the loads. As massive as the cast- steel wheels used

in the U.S. are, they would not seem to be a problem. Accident statistics,

however, indicate otherwise. According to the Accident/Incident Bulletin of

the FRA Office of Safety, broken wheels caused 134 accidents in the four

year period of 1985-1988, resulting in losses totaling $27. 5M. Besides the

direct and indirect cost of such problems, there is the threat to human life

and health due to the accidents themselves or the potential environmental

impact from the release of dangerous materials. Disruption to commerce at

many levels is almost inevitable.

During their lifetime, wheels see a wide variety of sometimes extreme

conditions. Among these are large static and dynamic mechanical loads,

large-scale frictional wear, high temperatures from braking operations,

environmental extremes, and exposure to potentially corrosive materials.

All these factors operate to initiate tread cracks or aggravate any existing

faults. According to the stress conditions (applied and residual), crack

growth can be very slow and gradual or rapid, even explosive. The relative

rarity of failures under all these extreme conditions speaks well for the

progress made in wheel design and manufacture.

Wheel improvements will continue, but it will not be possible to eliminate

completely the tread cracks that may, in the presence of tensile stresses,

lead to failure. For economic, environmental, and safety reasons,

replacement before failure is the preferred approach. Because of the costs

and uncertainties involved, retirement-for-cause is favored, whenever

possible, over replacement at predetermined intervals. Effective and

efficient nondestructive evaluation makes it possible to evaluate fitness

for- service. For railroad wheels, as in most other applications, the first

NDE test is visual examination by a skilled inspector. In practice,

however, this simple approach has severe limitations. Some of the problems

include: hidden flaws, inability to quantify flaw size, and unfavorable

conditions ( e . g , , position, lighting). The ideal test would be simple,

reliable, unintrusive, inexpensive, and operator independent. No available

techniques fulfill all these conditions perfectly, but ultrasonic testing

offers a possible major step in this direction.

The ultrasonic system examined here follows upon prior efforts at NIST and

elsewhere and the experience and expertise with electromagnetic-acoustic

transducers in this laboratory. After laboratory testing and development,

we built a prototype for delivery to the FRA. This will receive extensive

field testing and exposure to potential users. The desired goal is to

develop an instrument of value to the railroad Industry that private

industry would license for commercial production.

The plan for this NDE instrument was to have a sensor placed in a test rail

located on the outskirts of a rail yard, or on a dedicated track siding.

2
The train to be tested would simply roll over the test track (at speeds up

to 25 km/h or 16 mph) . The testing would be automatic and the report

produced at some desired remote site (e.g., the yard office). Maintenance

will likely be simple and minimal.

CONTRACT HISTORY

As the Fracture and Deformation Division of the National Bureau of

Standards, we first received a Federal Railroad Administration research

contract to develop nondestructive evaluation (NDE) procedures for railroad

wheels in September 1985. During the period of this work, we have been

renamed the Materials Reliability Division of the National Institute of

Standards and Technology. Our contract monitors have been M. Clifford

Gannett, Claire Orth, and Donald E. Gray. The current contract is

Reimbursable Agreement No. DTFR53-89-X-00018 with an effective date of

4/21/89.

Over the past few years, we presented the results of the work done under

this sponsorship at five meetings:

1. Review of Progress in Quantitative Nondestructive Evaluation,

Williamsburg, Virginia, June 1987.

2. Review of Progress in Quantitative Nondestructive Evaluation, La

Jolla, California, August 1988.

3. Nondestructive Testing and Evaluation for Manufacturing and

Construction, Urbana, Illinois, August 1988.

4. Third International Symposium on Nondestructive Characterization

of Materials, Saarbriicken, Federal Republic of Germany, October

1988.

5. American Society for Nondestructive Testing, fall conference,

Seattle, Washington, October 9-12, 1990.

Publications resulting from these conferences are:

1. "Flaw Detection in Railroad Wheels Using Rayleigh-Wave EMATs , " R.

E. Schramm, A. V. Clark, Jr., D. V. Mitrakovic, and P. J. Shull in

Review of Progress in Quantitative Nondestructive Evaluation . Vol.

7B, D. 0. Thompson and D. E. Chimenti, eds . , Plenum Press, New

York (1988), 1661-1668.

2. "EMAT Examination for Cracks in Railroad Wheel Treads," R. E.

Schramm, P. J. Shull, A. V. Clark, Jr., and D. V. Mitrakovic in

Nondestructive Testing and Evaluation for Manufacturing and

Construction . Conference proceedings, Urbana, Illinois, Aug. 9-12,

1988, H. L. M. dos Rios, ed. , Hemisphere Publishing Corp., new

York (1990), 373-380.

3. "EMATs for Roll-By Crack Inspection of Railroad Wheels," R. E.

Schramm, P. J. Shull, A. V. Clark, Jr., and D. V. Mitrakovic in

Review of Progress in Quantitative Nondestructive Evaluation . Vol.

8A, D. 0. Thompson and D. E. Chimenti, eds., Plenum Press, New

York (1989), 1083-1089.

3
4. "Crack Inspection of Railroad Wheel Treads by EMATs," R. E.

Schranon, P. J. Shull, A. V. Clark, Jr., and D. V. Mitrakovic in

Nondestructive Characterization of Materials . Proceedings of the

3rd International Symposium, Saarbriicken, FRG, Oct. 3-6, 1988, P

Hdller, V. Hauk, G. Dobmann, C. 0. Ruud, and R. E. Green, eds .

,

Springer-Verlag, New York ((1989), 421-428.

Most of this material was collected together and published as:

Report No. 18: Ultrasonic Railroad Wheel Inspection Using EMATs . Raymond E. Schramm and A. Van Clark, Jr., NISTIR 88-3906, Dec. 1988.

Other work done under this contract focused on the measurement of residual

stress in the rim of railroad wheels. The approach has been to use an

ultrasonic birefringence method, also based on EMATs. The results of this

parallel study are in a subsequent NISTIR 91-3968:

Report No. 23: Residual Stress Detection in Railroad Wheels: An

Ultrasonic System Using EMATs .

WHEEL INSPECTION SYSTEMS: OVERVIEW

Conventional Ultrasonics

In the mld-1970's, The Fax Corporation in Connecticut introduced the

WHeeLFAX* automatic ultrasonic system to examine each wheel as it rolled by

a checkpoint in a railyard [1-4]. Their ultrasonic probe, situated inside

the rail, is a pair of piezoelectric transducers within a liquid- filled

polyurethane boot. To aid the transmission of the probing signal into and

back out of the wheel, there are two nozzles spraying fluid onto the tread

as it passes. The basic idea, as in many ultrasonic approaches, is to

inject high frequency sound and then electronically analyze echoes generated

by any flaws present. The concept and engineering of this system are very

good, but the device has achieved only limited acceptance. The currently

active installations in this country are on a Florida-based railroad. There

are also plans for a test at the North Platte, Nebraska, railyard. Two

problems seem to have prevented large scale implementation: (1) a very

high rate of false positive indications, and (2) fragility, since the boot

is very susceptible to small cuts which release the pressurized liquid

couplant and disrupt operation. Unfortunately, as wheel treads abrade, wear

does develop occasional slivers which are short-lived but very sharp and

hazardous. Ongoing developments in electronics and signal processing are

improving performance

.

The use of trade names in no way implies endorsement or approval by

NIST and is included only for identification.

4
EMAT Ultrasonics - Germany

For more than ten years, the Fraunhofer Institute for Nondestructive Testing

(IzfP, Saarbrucken, Germany) has been working on an ultrasonic inspection

system based on the same concept and physics used in the conventional

approach, but taking a different approach to the transducers [5-8]. The

Germans employ noncontacting electromagnetic-acoustic transducers (EMATs)

that do not require an acoustic couplant to the wheel as do the conventional

transducers. EMATs simplify the mechanics of the rail mounting (since they

are generally smaller and more compact) , cut the number of false positives

(since they have a purer mode of operation and eliminate many extraneous

interfaces in the signal path) , and should be more durable (since there is

no pressurized rubber boot) . A few years ago IzfP installed a prototype

system in Wuerzburg for use on the high-speed German experimental Intercity

Express (ICE). This system has now been relocated to Hamburg.

EMAT Ultrasonics - United States

The IzfP system inspects a small number of forged wheels on passenger cars

and locomotives; these wheels all have tightly controlled wear profiles

required of high-speed passenger traffic. In our current project, NIST

seeks to use EMATs to inspect cast wheels on long freight trains which will

generally have a variety of tread wear patterns and damage states. The

major differences between German and U.S. applications of roll-by inspection

systems have led us to incorporate several major variations:

1. In-rail transducer configuration to accommodate various wheel

profiles

2. Use of a permanent magnet instead of an electromagnet to allow

operation on long trains.

3. Real-time, rather than off-line, signal processing for use in

heavy traffic situations.

Magnetic

One other method has been proposed. Instead of an ultrasonic probe, this

system from Wheel Checkers in Colorado passes a thin steel tape past the

tread of the moving wheel [9], This tape caries a continuous recorded tone

and the wheel is subjected to a strong magnetic field. Any perturbation in

the surface (i.e., a crack) will introduce a magnetic field gradient which

will distort the tone on the tape. This method has not received a field

trial, but the equipment is currently at the Transportation Test Center in

Pueblo, Colorado.

The following table contains some brief notes comparing the previous

ultrasonic systems with the one we have been developing.

5
References

[1] Inspect Wheels "In Motion," Progressive Railroading . Jan. 1974.

[2] Spotting the Defects in Railroad Wheels, Business Week , p. 44, Sept.

28, 1974.

[3] Cracked-Wheel Detector "Could Save Millions," Railway Systems

Control . May 1975.

[4] U.S. Patent 3,812,708: May 28, 1974, John Vincent Cowan, Gerald DeG.

Cowan, and John Gerald Cowan.

[5] Salzburger, H. J., and Repplinger, W. , Ultrasonics International 83 . conference organizers Z. Novak and S. L. Bailey (Butterworth & Co.

Ltd., Kent, Great Britain), pp. 8-12, 1983.

[6] Salzburger, H. J., Repplinger, W. , and Schmidt, W. , Deutsche

Gesellschaft fOr zerostdrunesfreie Prufune . Jahrestagung 25,

Berichtsband 10, Teil 1, pp.51-60, 1987.

[7] Salzburger, H. J., and Schmidt, W. , Mit vernetzten. intelligenten

Komnonenten zu leistungsfahigeren Mess- und Automatisierungssvstemen . Munchen, Oldenburg, pp. 124-133, 1989.

[8] German Patent OS DE 3505260 Al: Ultraschall-Prufvorrichtung zur

zerostorungsfreien Prufung der Laufflache von Schienenfahrzeugr&dern

Anmelder: Deutsche Bundesbahn.

[9] U.S. Patent 3,820,016: June 25, 1974, Marion W. Gieskieng.

6
Comparisons of In-Rail Ultrasonic Systems

WHeeLFAX IzfP NIST

Sensors

,

transducers

(Rayleigh

wave)

Piezoelectric (2),

sequential fire

(if time is

available)

,

unidirectional

EMAT using

electromagnet, 2

tandem serpentine

coils of 4 cycles,

approx. 24 random

wire turns

,

bidirectional

EMAT using permanent

magnet, 2 overlapping

serpentine coils of 7

ordered wire turns

bidirectional

Frequency 400 kHz 450 kHz 500 kHz

Wheel trigger Pressure sensor

at bottom of

fluid-filled

boot

Inductive pickup Membrane switch

operated by pressure

through foam pad

Wheel contact

(in rail)

Polyurethane boot

filled with

antifreeze, tread

sprayed with

detergent solution,

acoustic contact

through flexible

boot to wet wheel

Rigid assembly

pivots as wheel

passes over

Flexible cover and

coils (over foam)

conform to wheel

profile, magnet

rigidly mounted

inside rail

Footprint,

rail cut out

2hn x 5” wheel

contact

cut out * full rail

head width x full

rail head depth x

approx. 8” length

- - needs additional

rail for weight

bearing

Larger than NIST

cut out

lh" x 3V' wheel

contact - - cut out is full rail

head depth (slight

penetration into

rail web) - -remaining

rail head width is

sufficient for weight

bearing (needs no

additional support)

Analog signal Detected, log

amplified

Detected, log

amplified

Detected, log

amplified

Signal

processing

Digitize for

approx. 2 ms, find

peaks, extrapolate

to time-0 (remove

attenuation) , flaw

signal - amplitude

ratio of 1st echo

to 1st round trip,

near real time

Digitize & find

peaks, flaw signal

- amplitude ratio

of 1st echo to 1st

round trip, offline

processing

Peak detect for

approx . 2 ms , peaks

digitized, flaw

signal - amplitude

ratio of 1st echo to

1st round trip, near

real time

Continued

7
Continued

WHeeLFAX IzfP NIST

Output - - signals and

flags

1.

critical flaw

(amplitude ratio

adjustable)

2.

no test

3.

wheel size

1. critical flaw

(users set

amplitude ratio

empirically)

1.

critical flaw

(amplitude ratio

adjustable)

2

.

too many flaws (>3)

3.

"poor" metal (high

attenuation, no

2nd round trip)

4.

no test

5.

wheel size

Cables

,

connectors

Twisted pair,

screw terminals

Twinax and/or

Lemo connectors

Coax RG58C/U (3 @

10 m long) with BNC's

Installations Jacksonville and

Hialeah, FL, on

Florida East Coast

Railroad - test

site in North

Platte, NE for UP

Part of test

facility for ICE

(Intercity Express)

of the Deutsche

Bundesbahn - now in Hamburg

Field tests at TTC,

Pueblo, CO

History Patent in 1974 Installed 1987,

approx. 10 yrs.

development,

German patent

Began research in

1985, 1st field test

in 1989, prototype

delivery in 1991

Equipment

location

Pulser and preamp

at trackside,

processing in hut

20 m away, report

at yard office

2.5 km away (by

fiberoptic link)

Analog electronics

probably at track

side

10 m of cable to

analog and digital

electronics, report

can be remote

Guide rail Yes No? Probably not

Service

required at

track

Boot needs

replacement,

filling, and

bleeding when

slit; need to

refill spray tank

None Replace coil package

after wear (aim for

>1 week intervals) - requires 2 nuts and

3 BNC connectors

(approx. 5 min.)

Problems Collection of

magnetic dust at

EMAT, coil package

durability,

weatherization

8
IN-RAIL EMATS

EMATs (electromagnetic-acoustic transducers) are devices that generate and

detect sound energy directly in an electrically conductive specimen. A

major advantage of these devices is that they do not require the acoustic

couplants usually associated with piezoelectric transducers. This

simplifies operation and eliminates echoes and mode conversions that might

occur at the interfaces the signal would otherwise have to traverse.

Furthermore, they can operate effectively on rough and pitted surfaces.

Principles

To indicate basic EMAT operation, Fig.l shows a primitive element composed

of a wire conductor carrying a dynamic current Iw and a source of strong

magnetic field H0

. The current 1^ induces dynamic eddy currents Jw in the

metal conductor surface. H0 causes the deflection of the moving electrons

in a direction defined by J^Hq. The resultant Lorentz body forces, T,

generate ultrasonic signals that propagate radially into the specimen.

The polarization and propagation direction of an ultrasonic wave from an

EMAT are the result of the orientation of the electric and magnetic fields

and the arrangement of the primitive elements. For the examination of the

wheel tread, we want a Rayleigh wave, one that travels along the surface and

does not penetrate into the bulk of the wheel. To generate this ultrasonic

signal, a coil with a serpentine layout is necessary (Fig. 2). The

periodicity of the coil is the wavelength of the surface wave, in this

instance, 6 mm at 500 kHz. Repetition of the windings increases the ampereturns of the transducer for best signal strength. A flexible substrate and

support allows the coils to conform to the wheel's curvature for greatest

efficiency. This coil is currently laid out by hand, but automatic

production is available for large quantities.

Separate transmitter and receiver EMATs are usually physically separated and

each has its own magnet. We found we could minimize the size of the cutout

Figure 1. Primitive EMAT element.

9
6 MM: X - 1 MM

Figure 2. Schematic of the EMAT coils used to generate and receive Rayleigh

waves. A flexible substrate allows them to conform to the

curvature of the wheel.

Figure 3. Compact configuration of transmitter and receiver coils relative

to the magnet. The shift between the coils minimizes the mutual

shielding.

10
in the rail by stacking two of these serpentine coils and using only one

magnet. Careful staggering so that the wire legs of one coil show through

the open area of the other coil reduces the problem of mutual shielding.

Figure 3 indicates this arrangement, and the compact configuration that

results

While EMATs cannot operate efficiently at large liftoffs (distance to the

workpiece) , they can generally tolerate a separation on the order of

millimeters, and this is sufficient for roll-by inspection. Another EMAT

advantage is its high degree of selectivity, an ability to reject most

signals with an undesired polarization. This means a simpler echo pattern

and less confusion in data interpretation. In all the work of interest

here, the signal is a Rayleigh (surface) wave which travels around the outer

tread of the wheel and does not penetrate into the surface very far (“10 mm,

in this case)

During the course of field tests, various factors, such as loading, fatigue,

penetration of fine sand through the covering, etc., have caused the coil

windings to deviate noticeably from their original neat and symmetric

pattern (Fig. 2). In spite of these deformations, the signal strength did

not appear to diminish. The nature of the induction mechanisms and the

operational frequency contribute to a considerable robustness in use.

Configuration

During our laboratory research, the in- rail transducer evolved into a twopart device, magnet and coil package, mounted inside a test rail 2 m long.

The magnet here is a 52 mm x 26 mm x 31 mm block of Nd-Fe-B with a nominal

energy product of 0.28 MJ/m^ (35 MG-Oe). The field direction is along the

31 mm dimension and must be vertical in the track. A copper box surrounds

it, permitting mechanical attachment to the rail and shielding the magnet

from eddy currents generated by the coils. The exact configuration of this

box is not critical, but Fig. 4 gives some idea of the construction used

here. The copper is 0.8 mm (1/32 in) thick sheet cut into two sections.

Each surrounds three sides of the magnet and has ears extending from both

ends. The 1/4-20 bolts in the test rail pass through slots in the ears and

hold the magnet firmly in its pocket.

The coil package is a complex structure mounted on a bracket of aluminum

sheet 1.6 mm thick (Fig. 5). The vertical plate (approximately 100 mm

square) has two slotted holes for bolting to the rail head and holes for the

BNC connectors. The horizontal plate (approximately 40 mm x 80 mm) is the

support platform for two coils and the trigger switches.

The bottom layer is a pad of six membrane switches (Fig. 6) used to trigger

the electronics when a wheel is in position. The current connection of

these switches allows for setting up two independent systems. Until it is

determined that one configuration is better than the other, they can be

considered redundant. Trigger 1 is a pair of OR gates, right and left,

connected to make them an AND gate. The trigger occurs with the closure of

11
DIMENSIONS

cm inch

A 10.6 4 1/8

B 8.3 3 1/4

C 5.4 2 1/8

D 3.2 1 1/4

E 2.9 1 1/8

Figure 4. Sketch of copper box (two pieces) holding the magnet in the rail

pocket. The slots in the ears match the bolts in the test rail.

The magnetic field must be vertical (D direction)

.

either switch on the left and either switch on the right. Trigger 2 is

simply a pair of OR gates; the trigger occurs when either switch is closed.

There are independent connections to the two systems.

) Over the switches is a 5 mm thickness of resilient foam with small, closed

cells. This material has two functions. First, it compresses under the

load of the passing wheel and presses the flexible coils into the tread

profile. This close coupling insures the maximum signal amplitude. Second,

the foam transmits pressure to close the membrane switches under it.

Atop the foam is a thin (0.5 mm) sheet of fiberglass/epoxy composite. While

this material will flex to the wheel curvature, it provides mechanical

support for the coils and prolongs their fatigue life. Perhaps more

importantly, it supports the coil electrical connection, which have, so far,

proven to be the most fragile part of this package.

The two EMAT coils are on the top of this support sheet. They are shifted

with respect to each other, as noted above (Fig. 3), and fixed into

position.

Next is a thick (0.4 mm) layer of polyethylene tape. Its main purpose is

mechanical protection of the underlying coils.

The present overwrap for the switch and coil package is a coarsely woven

fiberglass cloth sprayed with a contact adhesive to keep it from unraveling.

This provides overall and first- level protection.

Since this coil package is in direct contact with the passing wheels, it

will suffer wear and eventually fail (probably due to a break within a coil

or a failure of a solder joint). With this in mind, the whole package is

expendable. Replacement involves only two nuts and three electrical

connectors

.

The test rail section (Figs. 7 and 8) has a pocket machined into the head to

hold the magnet, and a recess along the top of the head for the coil

package. A tapered transition into and out of this recess helps to transfer

12
HORIZONTAL PLATE

Supports

Bolts to rail

Electrical connectors

Figure 5. This aluminum bracket is the support structure for the coil

package. It is bent from a 1 . 6 mm sheet.

TRIGGER 2

Figure 6. Membrane switch pad used as a wheel trigger. These connections

give two separate triggers

13
Figure 7. Schematic of the machining necessary to put the EMAT transducers

in the rail. The deep pocket is for the magnet, while the tapered

recess along the top is for the coil package. The rail section is

67.5 kg/m (136 lb/yd) with a length of 1.7 m (65 in).

load smoothly to the remainder of the rail head for wheels with "false

flanges" and minimizes stress concentration and fatigue problems. Bolts on

either end of the pocket anchor the EMAT.

Figures 9 and 10 are cross sectional views of the EMAT within the rail and

indicate how the foam compresses into the recess while the remaining rail

head bears the weight. Figures 11 and 12 are photos of the coil package

assembly and the EMAT insertion into the test rail.

OPERATIONAL PRINCIPLES

There are four basic subsystems.

Transducer Package

The EMAT transmitter and receiver coils with their magnet are inside the

recess machined into the test rail. Integral to this package is the pad of

membrane switches that trigger in the presence of a wheel. The magnet

inside its copper box should be permanent. The coil package mounted on an

aluminum bracket is subject to wear and will need occasional replacement.

The coils and switches connect by coaxial cables to the analog electronics.

14
DIMENSIONS

cm inch

A

30 12

B

8.3 3 1/4

C

5.7 2 1/4

D

4.1 1 5/8

E 3-5 1 3/8

F 3.2 1 1/4

G 2.9 1 1/8

H 2.5 1

1 2.2 7/8

J 1.9 3/4

K 1.6 5/8

L 1.3 1/2

M 0 . 6 1/4

N 0.3 1/8

>

Figure 8. Dimension and details of pocket machined into test rail. The

transition section extended 30 cm (12 in) on either side of the

coil package. It tapered from a depth of 0.6 cm (1/4 in) at the

EMAT in a straight line back to the surface of the rail head.

15
COIL/TRIGGER

Figure 9. Cross section of EMAT system within the test rail. The

distance between the vertical plate and the box is adjusted

with washers to assure a 3-4 mm space between the end of the

horizontal plate and the lip of the tapered recess. (See

EQUIPMENT INSTALLATION.)

Figure 10. Cross section showing how the wheel compresses the coil

package into the machined recess while the remaining head

bears the weight.

16
Figure 11. A. Detail of the two EMAT coils on their fiberglass/epoxy

support.

B. Multiple layers on the horizontal plate of the coil

package

Figure 12. A. Magnet/copper box mounted on test rail.

B. Coil package in position.

17
Analog Electronics

There are two parts to this package

a. A high-current rf amplifier to produce gated pulses (10 cycles) at

500 kHz for the transmitter.

b. A high- gain, low-noise amplifier for the receiver signal. This

section also contains a detector and log amplifier.

Digital Electronics

This package processes the analog signal (the detected envelope of the rf)

.

The front end contains integrated circuits to:

a. Detect the peaks found in the first 2.5 ms of signal after the

trigger generated by the passing wheel. This is enough time to

complete the first two round trips (RTs) of the acoustic signal.

b. Digitize the amplitude and time of every peak found.

A microprocessor then uses the software in an EPROM to analyze this peak

information. Each wheel will generate one of five flags:

a. No test. There was no recognizable signal.

b. Poor metal. The signal was so highly attenuated that the second

round trip disappeared.

c. Critical flaw. There was a large flaw echo.

d. Multiple flaws. There were more than three flaw echoes.

e. Wheel OK.

Report Station

This is a small personal computer connected to the digital electronics by an

RS-232 bus. This unit receives the flag signals from the microprocessor and

prepares the final test report. It can be located in a location remote from

the rest of the equipment.

Figure 13 is a block diagram of these four subsections, while Fig. 14 is a

logic diagram of the overall process integrating the hardware and software

systems

.

In -Track EMAT

EQUIPMENT INSTALLATION

EMAT installation must follow a sequence.

1. Install the test rail in the track. The magnet pocket and tapered

recess must be on the outside.

2. Screw in the two threaded rods (1/4-20) on either side of the

magnet pocket. These are 3. 8 -4.

4

cm (1 1/2-1 3/4 in) long and

will seat firmly in the drilled and tapped holes with about 2.5 cm

(1 in) protruding. They do not have heads, but there is a

18
High-Current

Pulser

Low-Noise

Amplifier

3

-

| EMAT | | Trig

1 1 EMAT |

Peak/Time Signal

Detector Processor

7

Computer

Figure 13. Block diagram showing the relationship of the in-rail

transducer package, the analog electronics, the digital

electronics, and the reporting computer.

screwdriver slot in the end. To allow subsequent removal, it is

best to grease the threads

3. Insert the magnet into its copper box. The magnet must be

oriented so that its field is directed into the passing wheel

(perpendicular to the top of the rail head) ; north or south pole

must point directly up. The magnet is very strong and will jump

at any ferromagnetic material (e.g., the rail), and will pull

itself into the rail pocket. Use great caution to hold the magnet

firmly and avoid crushing fingers between rail and magnet. Ease

the box into its location; the two bolts should pass through the

slots in the box wings. A cautiously used screwdriver in the

pocket and behind the box may help maintain control.

4. Place a washer and nut on each bolt and tighten.

5. Determine the number of washers on each bolt that will provide the

proper spacing of the coil package from the outside edge of the

rail head. The horizontal plate (Fig. 5) has a cover to protect

the various components. To minimize cutting this cover, the far

edge (on the inside of the track) should be about 3-4 mm from the

edge of the tapered recess (Fig. 9). As the foam collapses under

the wheel weight, the cover folds into this space. Stack enough

washers (atop the nut holding the magnet in place) to maintain

this distance when the coil package is in place.

19
Hardware Software Flags

Figure 14. Logic diagram to show the operation of the systems shown in

Fig. 13. (RT = acoustic round trip signal.)

20
6. Position the coil package in the tapered recess. The slots in the

vertical plate will pass over the bolts and rest on the stack of

spacer washers. Tighten a locking washer and nut on each bolt.

When replacing a coil package, remove only the outer nut and locking washer

on the two bolts. Remove the old package, position the new one, and replace

the washers and nuts

Connections and Cables

Figure 15 shows the interconnections between the four subsystems. All the

cables are coaxial type with BNC connectors except for the RS-232 link to

the reporting computer.

The cable connecting the in- rail package ("track cable") is special because

of its length (10 m) , and its shield of metal braid. While this braid does

bind the three coax cables together and helps to protect them from

mechanical damage, its main function is electrical shielding to minimize

noise pickup. For this reason, on each end there are alligator clips that

should be attached to the frames of the coil package and the analog

electronics

While the individual lines within the track cable are identified, there is

very little or no difference in the signal if the transmitter and receiver

connections are exchanged. For the sake of consistency, though, it is

probably better to follow the ID markings.

The length and type of the track cable are important. Both transmitter and

receiver circuits have been tuned with this cable (10 m of RG-58C/U) to

account for its capacitance. A different length of cable will require

adjustments to this tuning . (See the ELECTRONIC SCHEMATICS section.)

The two cables between the analog and digital electronics can be any

convenient length and type. Within the specifications of the standard, the

same is true of the RS-232 cable going to the output computer.

On the reporting computer, there are special cables between CPU and monitor,

and also between CPU and keyboard. A printer is required only if a hardcopy report is desired after a train passes.

The digital oscilloscope in Fig. 15 is not necessary. It is merely a means

of visually monitoring the signals as they are generated. The trigger and

acoustic signal can be teed off either analog or digital electronics.

Although not indicated in Fig. 15, each of these electronic boxes requires

its own connection to a standard 110 V, 60 Hz power source. The computer

has its own separate plugs for the CPU and the monitor.

21
Report

Station

Digital

Electronics

(Digital

Oscilloscope)

rTM, • r—i i

i i

Jtrig inj

« i

r

i

Analog

Electronics

Transducer

Package

(in-rail)

Figure 15. Diagram of cable connections between the four subsystems.

The track cable is shielded by a metal braid. The digital oscilloscope is only a monitor and not required for

operation. The printer is required only if a hard-copy

report is desired.

22
EXPERIMENTAL RESULTS

Initial development of EMAT design and electronic equipment was done in a

static mode. Later, to simulate dynamic operations, we established a

standard gauge test track in our laboratory that was 2 m long (Fig. 16)

TTC provided us with several wheel sets (two wheels on an axle) that we

could roll back and forth over our sensor. Subsequently, we had the

opportunity to conduct field tests at TTC (Fig. 17).

Laboratory Tests

The major items to test on the in- track unit were:

1. Geometry.

a. The depth of the track recess necessary for the coil package.

b. The lateral location of the EMAT coils.

c. The effect of the lateral position of the wheel.

d. The depth of the foam necessary to accommodate the taper on

the wheel tread.

e. A preliminary look at the effect of variations in the tread

wear profile.

2. Trigger operation.

a. Pressure required to operate the membrane switches reliably.

b. Effect of the direction of wheel travel.

c. Repeatability.

3. Response to variation in the small range of velocities possible.

Of course, having a consistent and realistic source of acoustic signals was

necessary to understand how to interpret the information available. This

has to precede the development of any analysis software.

Acoustic Signatures

The oscilloscope traces in Fig. 18 are indicative of a few types of acoustic

signals recorded in the laboratory. All these waveforms are after

electronic detection and log amplification. The data are from 0.91 m (36

inch) diameter wheels.

Wheel OK

The wheel in Fig. 18A had been taken from service, but the tread was

recently machined to restore the profile. This wheel was in good condition

and the signal shows no flaw indications. Note the excellent signal/noise

ratio that give a very clean baseline and makes any acoustic signals very

prominent

The large spike at zero time is due to the gated rf pulse in the transmitter

coil inducing a pulse in the receiver coil which overloads its amplifier.

This is frequently identified as the "main bang." During this recovery

time, we are unable to see an acoustic echo. This signal merely indicates

that the system is operating.

23
Figure 16. Full scale test track established in our laboratory. Wheel

sets rolled over the EMAT. Total length was about 2 m.

Figure 17. Test site established on the Impact Track of the

Transportation Test Center in Pueblo, Colorado. The

electronics were housed In the trailer.

24
6 -

No Flaw

TIME (ms)

Figure 18. Typical analog signals. A and B are from the same wheel

before and after cutting an artificial flaw. The wheel in C

had been condemned for thermal checking and removed from

service

25
The signals occurring at approximately 1 and 2 ms are the first and second

round trips (RTs) . Depending on the metallographic condition of the wheel,

the acoustic pulse can travel many times around the wheel (we have seen as

many as 18), ©r very few. In the signal analysis, the arrival time of the

first RT is indicative of the wheel size. If this signal is not seen, no

test is possible and the digital system raises a flag (Fig. 14) . All

materials normally attenuate the signal amplitude, so each successive round

trip is smaller. If the microprocessor cannot find the second RT signal, it

raises a flag that the metal may be in very poor condition.

Single Flaw

The data in Fig. 18B are from the same wheel used in Fig. 18A, only now we

have machined a semicircular slot (2 mm deep and 12 mm long at the surface)

into the center of the tread. The additional signals are echoes from this

artificial flaw. There are multiple returns because there are multiple

acoustic paths for the signal to travel.

Our current algorithm looks for peaks between the "main bang" and the first

RT. If the flaw signal amplitude exceeds 20% of the first RT amplitude, it

raises a critical flaw flag. This 20% figure is based on very limited

laboratory experience, and experience will undoubtedly dictate later

adjustments

.

Multiple Flaws

Figure 18C shows the signal from a wheel condemned for thermal checking.

The likelihood of a single deep crack is small, since whatever causes one

crack will probably cause many more around the tread. If more than three

peaks appear between the "main bang" and the first RT, the analysis raises

the multiple flaws flag. Because of the high signal/noise ratio (Fig. 16A)

,

we have confidence that each peak here is a true indicator of a flaw.

Blind Spots

The signal in Fig. 18A shows no echo returns from any flaws. The

unavoidable presence, however, of the "main bang" would mask any indication

of flaws near the transducer- -the signal would simply be lost. The same

problem exists for any flaws exactly opposite the transducer; their echo

would be lost in the round trip. This means that a short section of the

tread at the top and bottom of the wheel (as it triggers the ultrasonic

pulse) will not be inspected. We estimate that these two hidden areas

amount to about 20% of the circumference.

In practice, this ability to see only about 80% of the tread may not prove

to be much of a problem. Our limited experience has indicated that real

flaws usually occur in large multiples. If this observation holds up in

field use, the hidden area will contain only a small number of the fla^ws

present. The analytical algorithm will likely raise a flag on the basis of

the remaining flaws detected. Of course, it is always possible to use two

sensors with a spacing of about a quarter of a wheel circumference.

26
Field Tests

Of course, no amount of laboratory work could substitute for actual tests on

a rail line. TTC provided us this essential opportunity on three separate

occasions. They installed our test rail on their Impact Track and

established a trailer to house the electronics so we could run week-long

tests on November 13-17, 1989, and May 14-18, 1990. On June 25, 1990, we

left the equipment on site for TTC personnel to operate until July 12. The

tests began with simply rolling wheel sets (as we did in the lab) to

establish initial setup, and graduated to running an engine and several

consists (Fig. 17). The rail cars were empty in some cases and 20%

overloaded in others. The wheels ranged from brand new to condemned from

revenue service.

Included among the things learned and the things modified as a result of

this experience:

1. There were two design changes in the aluminum bracket support of

the coil package. While this unit does not bear the weight of the

passing train, it does see enough load that the thickness must be

sufficient to avoid deformation. One wheel with a heavily worn

profile had so much overhang below the top of the rail head that

we had to remove a projection of the horizontal plate that

extended past the vertical plate.

2. Even though the rail flexed quite noticeably as each wheel passed,

the magnet in its copper box did have sufficient space that it was

not crushed or deformed.

3. As determined by TTC engineers, the modified rail section was

sufficient to support fully loaded cars, 143 000 kg (315 000 lbs)

on eight wheels.

4. To obtain some degree of reliability in the trigger system, we

advanced from a single membrane switch to the pad in Fig. 7.

5. On occasion, it was necessary to insert a 2-4 mm thick spacer

between the magnet box and the coil package. This raised the top

surface and generated more pressure through the foam pad to close

the membrane switches

6 . Some software changes improved the communication between the

digital electronics and the reporting computer.

7. Hardware changes in the digital electronics increased the time

resolution of the peak detector.

8. The high-current traction motors of the locomotive did often

generate noise in the baseline of the acoustic signal when they

were directly over the EMAT. However, even for the first wheel

after the locomotive, there was no indication of noise from this

source. The coils appear to be well shielded by the rail and the

wheel under inspection.

9. All the electronics functioned properly with power from a portable

10 kW generator.

10.

While one coil was cut by a wheel sliver, the major weakness in

the coil package appears to be in the fatigue life of the

electrical connections

27
11. With the redesigned switch pad (Fig, 6), the trigger system

appeared reliable up to about 24 km/h (15 mph) . At higher speeds

(32 km/h or 20 mph) , some wheels did not trigger the system - particularly, the second wheel on a truck. While such a speed

does not represent a significant restriction in a rail yard, this

limit is likely due, not to the switch, but to the mechanical

relaxation time of the foam pad above the switches. At the higher

speeds, this material does not have time to recover to its

original shape before the next wheel arrives. Should this become

a problem, some other foam would likely be preferable.

12. A guide rail was installed but its spacing had no effect.

Figure 19 demonstrates some specific examples of the data collected during

the first test in May. The train speed here was 8 km/h (5 mph), but the

appearance of the signal remained unchanged up to at least 24 km/h (15 mph).

The wheel in Fig. 19A was in normal service and had no known defects. The

wheels in Fig. 19B and C had been condemned and removed from use.

The signal baseline for a number of wheels with no defects was as flat as in

Fig., 18A, but Fig. 19A shows considerably more structure. This may indicate

the kind of threshold it will be necessary to specify in the analysis

software

.

The "scrape or gouge" signal in Fig. 19B shows strong echoes indicative of

a single large flaw (cf. Fig. 18B) . The "thermal cracks" signal in Fig. 19C

is similar to Fig. 18C in having a large number of significant peaks. Some

wheels with similar condemnation codes so attenuated the signal that the

round trip indicators were not detectable; in this case, the program would

raise the "no test" flag. The FRA report "Field Testing of Wayside Crack

Detection System" by Robert K. Larson, Jr. of TTC (Feb. 1991) contains

signal traces from many of the wheels tested.

ELECTRONIC SCHEMATICS

The special electronics designed and built for this project are currently in

two distinct packages.

Analog

The analog electronics make it possible for the EMATs to generate and detect

the ultrasonic signal. These two functions are physically separate and

distinct, but the circuits are mounted in one chassis with seven modules.

Puiser: Generates a gated (generally 10 cycles, but adjustable) pulse

of high current at 500 kHz when the in- track trigger closes

to signal the presence of a wheel at the test station. This

system also passes on a trigger to start the signal

processing in the digital electronics section (see below) . A

series capacitor at the final output tunes the transmitter

cable -EMAT system to achieve the maximum power transfer (Fig.

2QA) . The first five modules of the analog chassis house

28
In-Service

TIME (ms)

Figure 19. Typical analog signals from the first field test. The wheel

in A was in normal service with no known defects . The wheels

in B and C were condemned and removed from use. The type of

flaw and the AAR Why Made Code is indicated. Train speed was

8 km/h (5 mph)

29
0 200 400 600 800 1000

Frequency, kHz

Figure 20. Frequency dependence of impedance (Z) and phase (0)

.

The

EMAT is mounted in the rail and a wheel is located on top of

it. A tuning capacitor adjusted the resonant frequency of

the EMAT- track cable system to approximately 500 kHz.

A. Transmitter, series -tuned for minimum impedance.

B. Receiver, shunt- tuned for maximum impedance.

30

Impedance,

0

Impedance,

k

Q
this function. Figure 21 shows both the voltage and current

characteristics of the transmitter pulse.

Preamp: Provides amplification with a very low noise but high

(variable) gain (Fig. 22). The output delivered to the

digital electronics is a detected, logarithmically amplified

signal (see Figs. 18 and 19, A-C)A shunt capacitor at the

input tunes the receiver cable-EMAT system to minimize signal

loss (Fig. 20B)

The seventh module of the analog chassis

houses this unit.

Figure 23 is a schematic of the modules in the analog chassis, giving their

location and connections. The module numbers run from left to right looking

at the front of the chassis. Module six is empty. Figure 24 is a system

photograph.

Module 1 has the electrical control switches on the front panel. The on and

off sequences must always be:

ON 1. Power OFF 1. High Voltage

2. High Voltage 2. Power

Note: the high voltage is the last on and first off.

Among other logic operations, module 4 determines the number of rf cycles

generated in each power pulse to the transmitter. This is controllable from

1-10 cycles by a thumbwheel switch on the front panel. We have normally

operated with 10 cycles (setting - 0)

The gain of the preamplifier in module 7 is variable over a wide range with

a ten- turn pot on its front panel. We have generally used the mid- scale

setting of 400.

Figure 25 indicates the power and signal connections between circuits, Figs.

26-31.

Digital

The digital electronics process the signal generated by the analog system.

Again, there are two parts (on the same printed circuit board)

Peak detector: Extracts amplitude and time information of each

peak above a noise cut-off. The inputs are the

preamp signal and the pulser trigger.

Microprocessor: Uses the software in an EPROM to analyze these

peaks and determine whether a flaw is present.

This decision goes to the reporting computer.

In Fig. 24, the digital system is in the box sitting on top of the analog

chassis. Figures 32-33 are the schematics of each of the circuits.

List of Electronic Components

The following list identifies the components of both analog and digital

electronics (Figs. 24-34).

31
Figure 21. Voltage and current characteristics of the gated pulse

delivered to the transmitter EMAT.

Figure 22. Sample of the receiver EMAT rf signal from the pre-amp.

Figure 18 is after detection and log-amplification.

Expansion of the time scale would make it possible to see the

individual cycles. Subsequent round trip and echo signals

repeat until they are finally attenuated into the noise.

32
Trigger Analog

Out Signal

Trigger EMAT EMAT

In Transmitter Receiver

ANALOG CHASSIS

Figure 23. Schematic of the analog electronics chassis. This identifies

each of the modules, its location, and connections. (Front

view.

)

Figure 24. Photograph of all the special made parts of the crack

detection system: (1) analog- chassis with seven modules,

(2) digital unit sitting on top, (3) 10 m cable, and (4) EMAT

inside the test rail.

33
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List of Electronic Components, Analog and Digital Boxes

Quantity Reference Part Item Quantity Reference Part

1 SHI WHEEL SENSING SWITCH 37 1 C36 .01

3 . 01,02,04 114723 38 6 C37 , C4 5 , C4 6 , C85 , C97 , C134 .01

6 Cl , C2 , C6 , Cll , C101 , CIO

1000 39 2 018 , 019 1N41

1 R1 500 40 2 R25.R26 POT

1 R2 750 41 1 JP1 HEADER 2X2

3

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12 C3 , C4 , C7 , C9 , C12 , C14 , C19

C20, C29 , C30, C35 , C113

4.7 43 4 R27 , R54 , R60 , C84 10

44 1 012 759N

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C31, C39 , C42 , C43 , C77 , C79

C81 , C86 , C130

.1 45 5 R28 , R29 , R32 , R42 ,R43 100

46 2 R30.R31 5.11K

1 R4 820

47 1 L2 150NH

2 U3,U5 IAT7805 48 6 R33 , R34 , R41 , R68 , R90 , R91 10K

12 R6 , Rll ,R14 , R17 ,R40 , R44

R4 5 , R6 7 , R69 , R7 0 , R7 1 , R9 5 IK

49 2 R35.R38 6.8

2 R7.R12 3K 50 2 R36.R37 30

6 R8 , R13 , R20 , R2 1 , R22 , R89 3.3K 51 1 R39 7.5K

1 R9 2.2K 52 1 020 NTE109

3 D1 , D2 , D3 NTE168 53 1 Q9 2N4904

3 C16 , C17 , C18 INF 54 1 Q10 NTE190

4 T1,T2 ,T1B1,T2B1 FP34-340 55 1 Qll 2N3906

6 P3,P1,P2,P4,P5,013 CONN FRA8X2 56 1 Q12 NTE189

3 Q2.Q4.Q6 2N2222 57 2 T3,T4 1:9

3 Q1.Q3.Q5 2N6122 58 3 SW2 , SW5 , SW6 SW SPOT

' 2 07,08 TSC429 59 1 J2 OUTPOT

2 Q7.Q8 15N50 60 2 J3.J4 INPOT

4 D4 , 06 , D8 , D9 MOR1550 61 1 T5 XFMR

2 D5.D7 1N5248A 62 1 C44 SOOpF

2 R15.R16 3.3 63 1 C38 luf

1 J1 EMAT XHIT 64 1 C41 lOOpF

2 R18.R19 18 65 1 T6 200KVA

4 010,012,013,016 1N3600 66 1 SW3 POWER

4 011,014,015,017 1N5235 67 1 SW5A1 HIGH VOLTAGE

2 R23 , R24 560 68 2 SW5C1 , SW5B1 3P2T

4 C22 , C32 , C40 , R57 luF 69 2 022,023 LN28RCP

1 C33 5500pF 70 1 R46 12K

16 C28 , C23 , C24 , C25, C26, C27

C47 , C48 , C49, C50 , C51 , C52

100UF 71 1 D21 4 X 1N4006

C53 , C54 , C55 , C56

010

72 10 038,034,036,037,039,044,

045,046,049,060

74121

1 AH0013

73 2 040,048 74LS00

3 011,032,033 TL071

C34

74 5 R78,R79,R80,R81,R82 470

1 390

45
List of Electronic Components, Analog and Digital Boxes (cont.)

Item Quantity Reference Part Item Quantity Reference Part

75 3 C107,C109, C110 InF 113 2 RP1.RP2 4.7k

76 1 C108 150 114 1 U19 7821

77 1 U41 7474 115 5 L3 , L4 , L5 , L7 , L8 10UH

78 2 U42.U43 74LS192 116 9 C61 , C62 , C63 , C64 , C65 , C66 » 0. luF

C67 , C68 , C69

79 4 U31,U47,U50,U61 7404

117 1 U20 DS3695

30 4 C111,C80,C82,C112 47

118 1 U21 2764

81 6 R8 3-,R48,R49,R50,R53,R84 10k

119 1 XI 16MHz

82 2 R85 , R87 270

120 1 U22 87C51FA-1

83 2 C127 , C128 0.1 M

121 1 U23 75189

84 2 R86 , R88 360

122 1 U2 4 1488

85 1 U51 74S04

123 2 U26.U27 LM311

86 2 U52.U53 MCL2601

124 1 U29 5902

87 3 U54 , U55 , U57 74S140

125 1 U30 74LS76

88 1 U56 7 4HCT4 04 6 126 1 L6 lOOuH

89 1 C129 470PF

127 3 R51 , R55 , R58 lk

90 1 R92 5. IK

128 1 R52 2.4k

91 1 R9 3 50K

129 2 R56 , R59 3.3k

92 1 J7 TRIGGER INPUT

130 1 D26 1N4148

93 1 SW4 BCD SW

131 2 C87 , C83 33

94 13 C114 , C115 , C116 , C117 , C118

,

0.1 C119,C120,C121,C122,C123 132 3 C91 , C92 , C93 lOOnF C124,C125,C126

133 1 D27 MBD301L

95 1 J 6 TRIGGER OUT

134 1 U35 DG201

96 1 U59 NE555

135 1 R7 6 20K

97 1 R94 33K

136 1 R77 600

98 1 J8 TI

137 1 J5 TRIGGER

99 1 U62 14490

138 1 C102 4700

100 1 R96 15K

139 1 C96 6300

101 1 R97 430

140 1 C98 1800

102 1 Cl 3 2 2200

141 2 R7 2 , R73 2K

103 1 C133 2UF

142 2 R74.R75 120K

104 2 C131,C75 . 001

143 2 C99 , C100 47UF

105 1 U14 74LS373

144 1 JP3 SIGNAL

106 7 C57 , C60 , C76 , C78 , C88 , C89 , 10UF

C90 145 1 JP4 OUTPUT SIG

107 1 R4 7 8.2k 146 1 D28 1N4448

108 2 C58 , C59 30pF 147 1 T7 INDUSTRIJSKA ELECKTRONI1

109 1 U15 74LS08 148 1 C104 4700/40V

110 1 U16 6264 149 2 C105 , C106 1K/25V

111 1 U17 74LS138

112 1 U18 74LS245

46
SOFTWARE

Operation

The signal processing software within the box of digital electronics is

contained in an EPROM. Turning the power switch on activates the

microprocessor and its command program.

The computer serving as the report station has two power switches: CPU and

monitor. After the booting operation, it is necessary to load the

communication and data recording program from the internal hard disk. The

simplest way to do this is to enter the command "TRN." This executes a

batch file containing two commands:

CD TRN

COMTRN

Upon entry, the program needs a name used for the file storing the results.

Enter the file name for storing the data : XXXX

Sequential numbers (starting at 0) and the extension .DAT are added to this

name to create a separate file for each train. The screen then clears and

displays the name of the file prepared for the data about to be received as

well as function commands available (see below). The results from the

signal processor (received over the RS-232 interface) are then collected.

When the time since the last signal is one minute, the assumption is that

the end of the train is passed. The file is closed, its summary presented

on the screen, and the next file is prepared. Below is a screen sample:

FI or

* Main Result s

* F 3 cho

Total whee l

4 F 4 t 0 Good wheels 0 F 5 cha

No test 0 F 6 sor Wheel size 36" PGUP t PGDN t Esc yo

File name : XXXX1.dat

F 2 to operate current C0M1/2

ose window to look for more change the current file name

nge the file number to read

t and view the file results

o scroll one page up of data

o scroll one page down data

u want to terminate program

Mo test *** ** Poor metal   Many flaws**  ** p eep flaw * • Size 36 Wh# 1 Size 36 Uh# 2 Size 36 Uh* 3 Size 36 Uh# 4

an artificial

rolled over the EMAT four times. On each pass, the signal processor found

the echo from the slot and raised the "Deep Flaw" flag. Note that the data

displayed have been recorded on the hard disk in the file XXXX0.DAT; the

file XXXX1.DAT (noted on the top line) will' receive the data from the next

train.

47
The functional commands always displayed on the screen have several uses:

F1/F2 switch between communication ports 1/2.

/ F4 allows you to change the file name.

F5 allows you to change the sequence number on the file name.

F6 allows you to examine the data in the file named on the top line.

If a train's passage raises enough flags, it will not be possible to display

all the data on one screen.

F3 allows you to select one of the four flags, and see all the data.

PGDN scrolls down through the data.

PGUP scrolls up through the data.

Finally:

ESC exits the program, leaving you in the TRAIN subdirectory.

Program Listings

The first two programs, FTRAIN.C and FTIMER.C, were compiled and linked

using Franklin C-Compiler- 51 . Machine code for these two programs is

contained in the EPROM in the digital box.

The third program, COMTRN.C, was compiled in Microsoft Quick C. This is the

program in the reporting computer that accepts the test results from the

digital box then records them in a file and presents them on the monitor.

48
FTRAIN.C

#include "reg52.h"

#include "stdio.h"

#include "absacc.h"

#define CR Oxd /* Ascii carrlge return value */

#define port OxcOOO /* The A/D converter port address at C000H */

bit start_test; extern bit timer_flag; extern bit strt; extern int cnst; extern data unsigned int timerl_cnt;

extern data unsigned char count; data unsigned int wheel_cnt;

char deao;

void init();

void ass_data()

void flrst_rt();

void second_rtO

void eale_flav()

void result_flav()

void tran_data()

void clr_all();

void send_cnt()

data int forever;

void aain()

{init();

clr_all();

tlmer_flag-0;

forever-1;

while (forever) ( if (( timer_flag — 1 ) &&

/* Clear all parameters for the coming test */

If (

/* Main loop for every test */

( count >-3 )) { /* Timer 0 interrupt ocured now process the data

t imer_flag-0

ass_data()

/*

first_rt() /*

second_rt(); /*

calc_flaw()

/*

result_flaw()

/*

tran data()

/*

clr_all()

/*

demo-XBYTE [port]

/*

TH0-0xF4; /*

TLO—0x41;

tlmerl_cnt-0

wheel cnt++;

) /*

Organizetion of the collected data */

Look for first round trip */

Look for second round trip */

Calculate and process the flaw signal */

Assign the size and the flaw results to be transmited */

Transmit the data to host computer */

Clear all parameters for the coming test */

Read A/D converter for initilizetion */

Load count for timer_0 to generate 2ms sampling */

timerl_cnt >- 1220 ) ( if ( wheel_cnt !- 0

send_cnt()

wheel cnt-0;

) timerl_cnt-0

/*

{

End of timer_0 prosessing */

One minute pass since the last train */

) /* End of while */

void init()

(TC0N-0x45;

SC0N-0x52;

TMOD-Oxll;

IP-0x5

THO—0xF4

TLO—0x41

TH1-TL1-0

demo—XBYTE [port];

RS0-RS1-0;

IE-0x8F;

timerl_cnt-0;

RCAP2H-0xff;

RCAP2L-0xcb

T2C0N—0x30

TR2-1; TR1-1

DPH-OxcO; DPL-OxOO

P2-0; cnst-2

start_test-l

wheel_cnt-0;

)

/* Falling edge triggered external interruputs */

/* Communication 8 bit recieve on & TI is on */

/* Timer_0 16 bit timer mode 1, timer_l 16 bit auto reload for real time

/* Piriority for external interrupts */

/* Load count for timer_0 to generate 2ms sampling */

/* Generate 65536 cycles for real time timer 1 */

/* Read A/D converter for initilizetion */

/* Working area bank 0 for R0, R7*/

/* Opareting timer 1 as a real time as a timer in internal */

/* mode due to 12Mhz every 15.25 timerl_cnt - 1 sec */

/* Time setting for a Baud Rate generator of 9600 */

/* on timer two for RS - 232 communication */

/* Baud rate generator of 9600 to serial port */

/* Timer 1 is running as a real time clock */

/* The constant that determines the deep of the flaw */

/* counts the number of the wheels of the train */

49
FTIMER.C

#lnclude "reg51.h"

#lnclude "stdio.h"

#define CR Oxd /* Ascii carrige return value */

bit strt; bit timer_flag;

bit srtrip_ok;

bit deep_flaw, many_flaw;

int srtrip_num;

int frtrip_num

;

int cnst; char wheel_size;

data unsigned char count; data unsigned char low_byte [ 20 ] , high_byte [ 20]

;

data unsigned char read_peak[20]

;

unsigned int frtrip;

unsigned int rtrip;

unsigned char frtrip_amp, srtrip_amp;

data unsigned char flaw_size;

union tim_value

{ unsigned int i_read;

unsigned char r_value[2];

) u; struct read_data

( unsigned int time_read[ 20 ]

;

unsigned char peak_read[20]

;

unsigned char decision] 20]

;

) d; void ass_data()

(char i; for ( 1—0 ; i<-count; i++) { u. r_value [ 1

] -low_byte [ i ]

;

u . r_value [ 0

] -high_byte [ i ]

;

d. time_read[ i]-u. i_read;

d.peak_read(i]-read_peak(i]

;

)

)

void first_rt() /* This procedure searches for 1 round trip */

(int i; unsigned char max_amp-0; /* Look for the maximum amplitude also Dec 4 */

frtrip-0;

for ( i—1 ; i<-count; i++) ( rtrip-d. tlme_read[ i] -d. time_read(0]

;

/* Look for first round trip for 28" wheel 720 ]j 40 is */

if ( (rtrip >— 906) && (rtrip <- 1013) && (d.peak_read[i] >- max_amp ) ) ( max_amp-d.peak_read[l]

;

frtrip-rtrip;

d.decision[i]-l;

frtrip_num-i;

} /* End of 28" wheel */

/* Look for first round trip for 33" wheel 840 £ 40 is */

if ( (rtrip >- 1066) && (rtrip <- 1173) && (d.peak_read[ i ] >- max_amp ) ) ( max_amp-d . peak_read [ i ]

;

frtrip-rtrip

;

d.decision[i]-2;

frtrip_num-i;

) /* End of 33" wheel */

/* Look for first round trip for 36" wheel 920 - 40 & +60 is */

if ( (rtrip >- 1174) && (rtrip <- 1306) && (d.peak_read[ i] >- max_amp ) ) { max_amp-d . peak_read[ i ]

;

frtrip-rtrip;

d. decision] i] -3

;

frtrlp_num-i;

} /* End of 36" wheel */

frtrip_amp-d. peak_read[ frtrip_num] ; /* Amplitude of first round trip */

) /* End of first round trip seartch */

void second_rt()

(unsigned int srtrip;

int i; srtrip_ok-0;

srtrip-frtrip*2

;

for ( i—1 ; K-count;

rtrip-d. time_read( i

]

/* This procedure searches for 2 round trip */

/* The timing of first RT multi, by 2 £ 20 is */

i++) ( -d. time_read]0]

;

50
FTIMER.C (cont.)

if ( (rtrip >- srtrip-26) && (rtrip <- srtrip+26) ) { srtrip_num-i

srtrip_ok-l;

break;

)

) wheel_size—d.decision[frtrip_num]

srtrip_amp-d.peak_read[srtrip_num] ; /* Amplitude of second round trip */

) /* End of second round trip soertch */

void calc flaw<)

Iint j;

int prop_amp • 0; char fla*_nua • 0; prop_aap-(frtrip>_aap*cnst)/10; /* Constant of 20% of first RT to svslusts s Deep Flaw */

for ( J-l; j<frtrip_mm; J-m-) ( rtrip-d. tlme_read( j

] -d. time_read(0]

if ( (rtrip <- 200) ) ( ”/* Skip deadtino of lSOts for signal recovery */

continue;

) els# ((lasjHBM;

if ( d.peek_resd[j ] >— prop_aap ) deep_flaw-1

if ( flaw nuB >- 3 ) nany flaw - 1;

1 >

) /* End of calculation the flaw signals */

void result flaw()

(if ( frtrip —0)1 /* There is no first round trip */

wheel_size-'0'

flaw slze-'l'

) if ( srtrip_ok — 1 ) ( /* There were a second round trip */

wheel_s ize-wheel_s ize+0x40

if ( deep_flew — 1 ) flew_size-' 3*

if ( nany_flaw — 1 ) flaw_size-'4'

if ( ( deep_flew — 0 ) && ( menyflaw — 0 )) flaw_size-' 5'

) if (( srtrip_ok — 0 ) && ( frtrip ! — 0 ) ) | /* There is no second round trip means poor metal

wheel_s ize-wheel_size+0x40

flaw size-' 2';

)

)

void tran data()

( while(ITI); /* Transmit the wheel size first */

TI-0;

SBUF-wheel_size

whlle(ITl); /* Transmit the flaw report second */

TI-0;

SBUF-flaw_size

whlle(ITl); /* Transmit the CR to end transmition */

TI-0; SBUF-CR;

»

void clr all()

( strt-0;

deep_flaw-0

many_flaw—0

srtrip_num-0

frtrip_num-0

wheel_size-0;

flaw_size-0;

rtrip-0;

frtrip_amp-0;

srtrip_amp-0

)

timarO() interrupt 1 using 0

{ EA-0;

timer_flag“l;

TR0-0;

, “*1: Eiyo

51
COMTRN.C

# include

# include

#include

include

#include

include

include

include

<dos .h> <malloc .h> <stdio.h>

<stdlib.h>

<time .h> <conio .h> <bios . h>

<graph . h>

define C0M1 0 define COM2 1 define FI 0x3b

define F2 0x3c

define F3 0x3d

define F4 0x3e

define F5 0x3

f

define F6 0x40

define F7 0x41

define F8 0x42

define F9 0x43

define F10 0x44

define CURUP 0x48

define CURDN 0x50

define PGUP 0x49

define PGDN 0x51

define Esc 0x1

define EOI 0x20

define peek( addr ) (*(unsigned char far *)addr)

/* Stack and pointer checking off */

pragma check_stack( off ) pragma check_pointer ( off ) enum BOOLEAN { FALSE, TRUE };

/* Prototypes for interrupt functions */

void (interrupt far *oldcomunl)( void ); void (interrupt far *oldcomun2)( void ); void interrupt far newcomunl( void )

;

void interrupt far newcomun2( void );

int read_flag - FALSE; char data_in( 1000] , data_read[ 1000]

;

char *data_ptr;

int count, countl, forever-1;

char key_press ,buffer[1000]

;

struct videoconfig vc;

int com2_set-0, com2_on-0, file_num—0; unsigned char old_int_cont , new_int_cont

;

char nam_file[17] , nam_file_in( 10]

;

char data_end[] - "NUM - "; char *str_find_ptr

;

int wheel_count, good_wheel, wheel_size;

char seps[] - "\r\n"

;

struct wheel_info

( char info [ 3 ]

;

char size;

char flaw;

) wheel [ 1000]

;

int no_testl , deepflawl , poor_metall , many_flawl

;

int no_test[1000] ,deep_flaw[1000] ,poor_metal[1000] ,many_flaw[1000]

;

int i, whe_size, pgup-0, pgdn-0;

char choose_wdo;

int page_tot, page_nub_n, page_nub_p, page_nub_m, page_nub_d;

main( )

( unsigned key, scan;

int kread - _KEYBRD_READ

;

int kready - _KEYBRD_READY

;

int kshiftstatus - _KEYBRD_SHIFTSTATUS

;

/* If bit 4 of the byte at 0x0040:0x0096 is set

if( peek( 0x00400096 ) & 0x10 ) the new keyboard is present */

52
COMTRN.C (cont.)

kread - NKEYBRD READ; kready -~_NKEYBRD READY; kshiftstatus - _NKEYBRD SHIFTSTATUS;

count-count 1-0

init_conl( )

_gatvldaoconflg( &vc )

_se tvldeoaode ( _TEXTC80 ); system( "els" )

naaa_flle()

naw_fila()

_sa ttextwlndow( 3, 22, 11, 57);

_settextcolor(0)

_satbkcolor(llL)

sprlntf (buffer," FI or F2 to operate current C0H1/2 ");

_outtext( buffer ); eprlntf (buffer, " F3 choose window to look for more ");

_outtext( buffer )

sprintf(buffer , " F4 to change the current file nane ");

_outtext( buffer )

sprintf (buffer , " F5 change the file number to read ”);

_outtext( buffer )

sprintf (buffer , " F6 sort and view the file results ");

_outtext( buffer )

sprintf(buffer , " PGUP to scroll one page up of data ");

_outtext( buffer )

sprintf (buffer, PGDN to scroll one page down data ");

_outtext( buffer )

sprintf (buffer , " Esc you want to terminate program ");

_outtext( buffer ); while ( forever )

(s tr_find_ptr-data_in

str_find_ptr-strstr( str_find_ptr, data_end);

if ( str_find_ptr !- NULL ) ( str_find_ptr-strchr( str_find_ptr, 13 ); if (( str_find_ptr !- NULL ) && ( read_flag)) { read_flag- FALSE; putchar(7)

putchar(7)

putchar(7)

putchar (7)

putchar (7)

save_file()

count-0

read_file()

sort_data()

view_data()

file_nua++; new file()

)

)while( 1 ) ( if ( _bios_keybrd( kready )) break;

if ( read_flag ) { if ( ! ( _bios_keybrd( kready ) ) ) ( scan-0;

goto cont;

)

)

) /* _bios_keybrd( kread ); */

key - _bios_keybrd( kread )

scan - key » 8; cont: switch ( scan )

{case F3: change_wlndow()

break; case PGDN: pgdn-1

select_window()

break; case PGUP:

53
COMTRN . C (cont.)

pgup-l

;

select_window( )

;

break; case F4: name_file ( )

;

new_f ile( )

;

break; case F5: change_num()

;

new_f ile ( )

;

break; case F6

read_file()

;

sort_data()

;

view_data( )

;

break; case FI: com2_set-0;

init_coml()

;

break; case F2; init_com2()

;

break; case Esc:

if ( com2_on) ( dos setvect( 0x0b, oldcomun2 ); ) _dos_setvect( 0x0c , oldcomunl ); outp(0x21 , old_int_cont)

;

setvideomode (_DEFAULTMODE)

;

exit(l)

;

break;

default:

break;

}

)init_coml()

{unsigned char dlab;

_bios_serialcom( _COM_INIT,COMl,_COM_CHR8 | _COM_STOPl | _COM_NOPARITY | _COM_9600 ); oldcomunl - _dos_getvect( 0x0c ); /* Changing the comun. intr. handler */

_dos_setvect( 0x0c, newcomunl ); dlab-( inp(0x3fb) & 0x7f)

;

outp(0x3fb,dlab)

;

outp(0x3f9 , 0x01)

outp(0x20,0x4a)

;

old_int_cont-inp(0x21)

;

outp(0x21, (old_int_cont & Oxef));

/* Read dlab bit from line control register enables intr.

/* Set dlab-0 for fourther communication handling */

/* Enable receive data interrupt */

*/

outp(0x3fc,0x0b)

;

/* Set out2 in modem control register enables intr. */

init_com2 (

)

(unsigned char dlab;

_bios_serialcom( _COM_INIT , COM2 ,_COM_CHR8 | _COM_STOPl | _COM_NOPARITY | _COM_9600 ); oldcomun2 - _dos_getvect( 0x0b ); /* Changing the comun. intr. handler */

_dos_setvec't( 0x0b, newcomun2 ); dlab- (inp( 0x2 fb) & 0x7f); /* Read dlab bit from line control register enables intr. */

outp ( 0x2 fb, dlab ) ; /* Set dlab-0 for fourther communication handling */

outp(0x2f9 , 0x01) ; /* Enable receive data interrupt */

com2_set-0xl00

;

outp(0x21 , (old_int_cont & 0xf7));

com2_on-l

;

outp(0x2fc,0x0b) ; /* Set out2 in modem control register enables intr. */

)

name_file(

)

{ _settextwindow( 24,14, 25, 66);

_settextcolor(0)

;

_setbkcolor ( 11L)

_clearscreen( GWINDOW )

;

sprintf (buffer , " Enter file name for storing the data into : ");

54
COMTRN.C (cont.)

_outtext( buffer )

scanf("%s" ,nam_file_in)

_setbkcolor(OL)

clearscreen( _GWINDOU )

change_num()

( _settextwlndow( 24,26, 25, 54);

_settextcolor(0)

_setbkcolor(llL)

sprintf (buffer , " Enter a new file number : ") _outtext( buffer )

_settextposition(l , 28)

scanf ("%d" , &file_num)

_setbkcolor(OL)

clearscreen( _GWINDOW )

new_file()

(char strg[3];

itoa(file_nua, strg, 10)

nam_file(0]-'\0'

strcat(nasa_file , nam_file_in)

strcat(nam_file , strg);

s treat ( nam_fi le , " .dat")

_settextwindov( 2, 29, 2, 53);

_setbkcolor(0L)

_clearscreen( _GWINDOW ); _settextcolor(7)

_setbkcolor(13L)

_settextposition(0,0)

sprintf (buffer , " File name : %s ",nam_file);

_outtext( buffer )

read file()

(FILE *file_in;

if( (file_in-fopen(nam_file, "rb" )) — NULL )

( printf( "Can't open input file” ); exit( 1 );

)

data_ptr-data_read

while ( ! feof ( file_in ) )

(*data_ptr-fgetc( file_in ); data_ptr++;

) fclose( file in );

)

save file()

(FILE *file_out;

if( (file_out-fopen(nam_file , "wb" )) — NULL )

( printf( "Can't open input file" ); exit( 1 );

)for ( i—0 ; i<-count; i++) ( fputc( data_in[i], file_out );

) fclose( file_out );

)

change window (

)

{ _settextwindow( 24,13, 25, 68);

_settextcolor(0)

_sstbkcolor(HL)

55
COMTRN.C (cont.)

sprintf (buffer , " Type 'n' , 'p', 'm' or 'd* to choose current window

_outtext( buffer )

;

_settextposition(0 , 53)

;

choose_wdo-getche()

;

_setbkcolor(OL)

;

_clearscreen( _GWINDOW )

;

) view_data(

)

(

)

page_nub_n-page_nub_p-page_nub_m-page_nub_d-0;

_settextwindow( 4, 2, 9, 20);

_settextcolor(0)

;

_setbkcolor(10L)

_clearscreen( _GWINDOW )

;

_setbkcolor(13L)

;

sprintf (buffer , " * Main Results * ");

_outtext( buffer )

;

_setbkcolor(10L)

;

_settextposition( 2,0);

sprintf (buffer , " Total wheels %3d " , wheel_count)

;

_outtext( buffer )

;

_settextposition(3 ,0)

;

sprintf (buffer, " Good wheels %3d "

, good_wheel)

;

_outtext( buffer )

;

_settextposition(4,0)

;

sprintf (buffer, " No test _outtext( buffer ); _settextposition(5 ,0)

;

sprintf (buffer , " Wheel size %d\" " , wheel_size)

;

_outtext( buffer )

;

view_no( )

;

view_poor ( )

;

view_many ( ) view_deep()

%3d ", no testl)

;

");

view_no(

)

( _settextwindow( 12, 3, 23, 19);

_settextcolor(7)

;

_setbkcolor(15L)

_clearscreen( _GWIND0W )

;

_setbkcolor(9L)

;

sprintf (buffer , " *** No test *** ");

_outtext( buffer ); _setbkcolor(15L)

;

_settextcolor(4)

_settextposition(2 ,0)

;

page_tot-(no_testl/10)+l

;

if ( (page_tot > 1 ) && ( pgdn | | pgup ) ) { if ( pgdn ) ( pgdn-0

;

page_nub_n++

;

if ( page_nub_n >— page tot ) page_nub_n- - ;

Ielse { if ( pgup ) ( pgup-0

;

page_nub_n- -

;

if ( page_nub_n < 0 ) page_nub_n-0

;

)

)

)for ( i-page_nub_n*10+l ; i<- 10* ( page_nub_n+l ) ; i++) { if ( i > no_testl ) break;

sprintf (buffer , " Wheel numb. %3d ", no_test[i]);

_outtext( buffer )

;

) if ( i < no_testl ) ( _settextposition( 12,2)

;

_settextcolor(0)

;

_setbkcolor(14L)

;

sprintf (buffer , "** More data **");

_outtext( buffer )

;

56
COMTRN.C (cont.)

)

)

view_poor(

)

{ _settextwindow( 12, 22, 23, 38);

_settextcolor(7)

_setbkcolor(15L)

_clearscreen( _GWINDOW )

_setbkcolor(9L)

sprintf (buffer , "** Poor metal ** ");

_outtext( buffer )

_setbkcolor(15L)

_settextcolor(4)

_settextposltion(2 , 0)

page_tot-(poor_metall/10)+l

if ( (page_tot > 1 ) && ( pgdn || pgup )) { if ( pgdn ) { pgdn-0

page_nub_p++

if ( page_nub_p >— page_tot ) page_nub_p-- ;

)else { if ( pgup ) { pgup-0;

page_nub_p - -

if ( page_nub_p < 0 ) page_nub_p-0

)

)

)for ( i-page_nub_p*10+l ; i<- 10*(page_nub_p+l) ; i++) ( if '( i > poor_metall ) break;

whe_size-28+( (wheel [poor_metal [ i] ] .size) -0x41)*4;

sprintf (buffer , " Size %2d Wh# %3d ",whe_size, poor_metal[i] )

_outtext( buffer ); "

) if ( i < poor_metall ) { _settextposition(12 , 2)

_settextcolor(0)

_setbkcolor(14L)

sprintf (buffer , "** More data **”); out text ( buffer )

)

view_many()

{ _settextwindow( 12, 41, 23, 57);

_settextcolor(7)

_setbkcolor(15L)

_clearscreen( _GWINDOW )

_setbkcolor(9L)

sprintf (buffer , * ** Many flaws** n ); _outtext( buffer )

_settextcolor(4)

_setbkcolor(15L)

_settextposition(2,0)

page_tot-(many_flawl/10)+l

if ( (page_tot >!)&&( pgdn | | pgup )) { if ( pgdn ) { pgdn-0;

page_nub_m++

if ( page_nub_m >— page_tot ) page_nub m- - ;

)else ( if ( pgup ) ( pgup-0;

page_nub_m- -

if ( page nub_m < 0 ) page_nub_m-0

)

)

)for ( i-page_nub_m*10+l ; i<- 10*(page_nub_m+l) ; i++) ( if ( i > many_flawl ) break;

57
COMTRN . C (cont.)

whe size-28+( (wheel (many_flaw [ i ] ] .size) -0x41) *4

;

sprintf (buffer," Size %2d Vh# %3d ",whe_size, many_flav[ i ] )

;

_outtext( buffer );

) if ( i < many_flawl ) ( _settextposition(12 , 2)

;

settextcolor(O)

;

_setbkcolor(14L)

;

sprintf (buffer,”** More data **");

outtext( buffer );

)

)

view_deep(

)

_settextwindow( 12, 60, 23, 76);

_settextcolor (7)

;

_setbkcolor(15L)

;

_clearscreen( _GWINDOW )

;

_setbkcolor (9L)

;

sprintf (buffer," ** Deep flaw ** ");

_outtext( buffer ); _settextcolor (4)

;

_setbkcolor(15L)

_settextpositlon(2 ,0)

;

page_t°t— (deep_flawl/10)+l

;

if ( (page_tot > 1 ) && ( pgdn || pgup )) ( if ( pgdn ) { pgdn-0;

page_nub_d-H-

;

if ( page_nub_d >- page_tot ) page_nub_d-- ;

)else ( if ( pgup ) ( Pgup-0

;

page_nub_d- -

;

If ( page_nub_d < 0 ) page_nub_d-0

;

)

)

)for ( i-page_nub_d*10+l ; i<- 10*(page_nub_d+l) ; i++) ( if ( i > deep_flawl ) break;

whe_size-28+( (wheel [deep_flaw [ 1] ] .size) -0x41)*4;

sprintf (buffer , " Size %2d Wh# %3d ",whe_size, deep_flaw[ 1] )

;

_outtext( buffer ); ~

) if ( i < deep_flawl ) ( _settextposition(12,2)

;

_settextcolor(0)

;

_setbkcolor(14L)

sprintf(buffer, "** More data **");

_outtext( buffer );

)

se lec C_window (

)

{ if ( choose_wdo

if ( choose_wdo

if ( choose_wdo

if ( choose_wdo

'n' || choose_wdo —

'p' || choose_wdo —

'm' || choose_wdo —

'd' || choose_wdo —

'N' ) view_no();

'P' ) view_poor();

'M' ) view_many()

;

'D' ) view_deep();

sort_data()

(int num_a , num_b , num_c , max_value

;

int i

;

char *num_str;

num_str-data_read;

nuin_str+-strcspn( num_str, data end)

;

num_str+—strspn( num_str, data_end)

;

num_str-strtok(nuia_str , seps) ; wheel_count-atoi(num_str)

;

num_s tr-da ta_read

;

58
COMTRN.C (cont.)

num_str-strtok(data_read, seps)

for ( 1—1 ; K-wheel_count; 1++) ( wheel[l] . size-*num_str;

wheel [i] .flaw-*(num_str+l)

num_str-strtok(NULL,seps)

Jnua_a-num_b—num_c-0

for ( 1-1; l<-wheel_count; 1++) ( if ( wheel[i) .size— 'A') num_a++;

If ( w'neel[ 1] .size—-'B' ) num_b++;

If ( wheel! 1] .size— ’C') num_c-H-;

)max_value-max( nua_a , num_b ); max~value-aax( aax_value , num_c )

if (max_value—nua_a) wheel_size—28; if(max_value—num_b) wheel_slze—32; if (max value—num_c) wheel_size—36; no_testl-deep_flawl-poor_metall-many_flawl-good_wheel-0;

for ( 1—1 ; i<-wheel_count; 1++) ( if ( wheel[i] . flaw—' 1* ) ( no_testl++;

no tesc[no testl]-l;

) "

if ( wheel[ 1] .flaw—'2') ( poor_metall++

poor metal [poor_metail]-!;

)if ( wheel [i]. flaw—'3') { deep_flawl++;

deep flaw[ deep flaw1

] -i

)if ( wheel! i] .flaw— '4') < many_flawl++

many_flav!many flavl]-i;

)if ( wheel! 1] • flaw— ' 5'

) good_wheel++;

)if ( no_testl > 11 ) choose_wdo - 'n'; if ( poor_metall > 11 ) choose_wdo - 'p'

if ( many_flawl > 11 ) choose_wdo - *m'

if ( deep_flawl > 11 ) choose_vdo - ' d*

void interrupt far nevcomunlO

(char Hr;

ilr-(lnp(0x3fa) & 7);

if( ilr — 4 )

( data ln(count+l]-'\0'

read~flag-TRUE

data_in( count ]-inp( 0x3f8); count++; outp(0x20,EOI) ; /* End of interrupt to 8259 */

)

)

void Interrupt far nevcomun2()

(char Hrl;

Hrl-(inp(0x2fa) & 7);

if( Hrl — 4 )

{ data_in!count+l]-*\0'

read_flag-TRUE

data_in{ count ]-inp( 0x2f8)

count++; outp(0x20, E0I) ; /* End of interrupt to 8259 */

)

) END

59
CHECKLIST

1. EMAT installed in track

2. Coil package position adjusted horizontally and vertically.

3. All connecting cables (coaxial cables, RS-232) installed

4. Ground clips on both ends of track cable connected.

5. All electronics powered on

6. Reporting computer booted-up and control program loaded

TROUBLE SHOOTING

Some potential problems with possible solutions include:

1 . No trigger

2. Trigger but

no signal

Check trigger cable - use multimeter to make sure

switch is closing when pressure is applied to coil

package (have someone step on the transducer in the

rail) - switch to alternate trigger on coil

package, if necessary - replace coil package if

neither trigger closes

If triggers test OK, they may not be getting

sufficient pressure from the rolling wheel (e.g.,

the resilient foam under the coils is collapsing) - loosen the two nuts holding the coil package, raise

it up, insert a nonferritic spacer (“3-4 mm thick)

between its horizontal plate and the magnet, lower

it into place, and tighten nuts

Check continuity of both transmitter and receiver

coils with multimeter (at coil package or at end of

track cable) - DC resistance should be 6-7 0. If

either coil is broken (open) or shorted, replace

coil package

Check that high voltage at analog box is ON

Check integrity of any exposed cables (rodents like

to chew on them)

60
3.

Noise on Check that track cable shield connections to

analog signal aluminum bracket of coil package and frame of

analog electronics box - check that all BNC's are

tight - use ground straps to connect frames of all

boxes of electronics - install a power conditioner

on 110 V power supply

4. Cuts at the

outer edge of

the coil package

cover

Increase spacing between the edge of the coil

package and the lip of the tapered recess by

increasing the number of washers between the magnet

nuts and the vertical plate.

FUTURE CONSIDERATIONS

1. To locate the reporting computer at a remote location, the RS-232 link

with the digital electronics needs to be replaced with:

a. RS-422 or RS-485 link,

b. fiberoptic link,

c. telephone line with modems, or

d. microwave link.

2. The digital electronics can probably be repackaged into the empty

module in the analog electronics rack.

3. The BNC connectors need to be replaced with a system that will be less

subject to corrosion during long-term field use. Possibilities include

simple twisted pairs with screw terminals, or more elaborate MIL- type

connectors

4. The coil package needs to be made weather-proof (or at lest moisture

resistant). Currently, the resilient foam may absorb some water, and

the several tapes inside will not withstand extensive exposure to

moisture

5. The Nd-Fe-B magnet needs a protective coat against rusting.

6. A method of wheel flagging other than sequence numbers will be

necessary. Possibilities are video taping (as done by WHeeLFAX) , or

firing paint pellets at the wheels.

7. It may be desirable to bury the analog and digital electronics in a

shielded box next to the track to minimize the travel distance of rf

and low-level signals.

8. One possible redesign of the in-rail transducer would give it a hard

surface (highly resistant to wear) and have it rids on pivots or

compression springs to accommodate the moving wheel. This would cut

maintenance even further.

61
9 . It will eventually be necessary to incorporate a switching mechanism

that will sense a train as it approaches the inspection site and turn

the equipment on.

10. Field experience may indicate some changes in the processing algorithm:

a. Do we need to adjust the echo/RT amplitude ratio of 20% for

critical flaws?

b. Is three the right number at which to raise the multiple flaw

flag?

c. Should the amplitude be adjusted for the distance the signal

has traveled (as measured by its arrival time)? The first

and second RT amplitudes can be used to measure the

attenuation.

d. Is there any value to processing the flaw peaks between the

first and second RTs?

11. The coil in Fig. 2 is presently hand-wound. We need to explore

automated production for larger quantities

.

12. Inspection of the wheels on both side of the train is obviously

necessary, so test sites will be necessary in both tracks.

13. Since the "main bang" and round trip signals (Fig.l8A) mask about 20%

of the potential flaw signals, it would require two sensors in the same

track to assure 100% tread coverage. Locating the EMATs a quarter of a

wheel circumference apart will prevent their blind spots from

overlapping. It is also likely that a correlation of the analyses of

the two probes would increase reliability.

14. Lightning will be a danger to this system. Nothing will protect

against a strike directly on the transducer, but it would be desirable

to isolate from pulses traveling along the rail from remote hits. The

railroads are likely to have considerable experience with this problem.

15. The current software does not cover the wheel sizes used in

locomotives. Should the electronic noise from the traction motors

prove not to be too great so that good measurements are possible, this

can easily be modified.

16. The trigger system that indicates the wheel is in position needs

improvement for mechanical and electrical reliability. The most likely

current candidate is a strain gage bridge on the rail web to sense the

shear load as the wheel passes over the EMAT. Other possibilities

include noncontact inductive sensors.

17. A hybrid system including these EMATs and other sensors (such as

accelerometers) might provide an even more complete picture of wheel

fitness

.

62
OTHER POTENTIAL APPLICATIONS

The energy of Rayleigh waves is largely confined to the two dimensions of a

surface as opposed to body waves that spread through three dimensions. The

Rayleigh wave signal, therefore, attenuates as the square of the distance

traveled, rather than the cube. In our early work, we saw as many as 13

round trips (p. 26) of the wheel circumference. This amounts to about 55 m

(180 ft) total travel.

This long distance capability of the EMAT described in this report suggests

the possibility of ultrasonic inspection of large scale structures where it

would be difficult or time consuming to scan a probe near all potential

surface cracks. For example, a single, linear sweep of the transducer would

inspect the large steel panels used in the construction of ship hulls or

chemical storage tanks. Since EMATs require no acoustic couplant and little

or no surface preparation, they readily lend themselves to field use.

ACKNOWLEDGMENTS

A considerable number of people have been involved in this work in various

ways and at various time.

From the FRA, Clifford Gannett, Claire Orth, and Donald Gray have all

provided valuable guidance.

From TTC we received a great deal of help and cooperation in obtaining test

wheels and rail sections. Of course, the field tests would have been

impossible without their collaboration. Our main contact has been Robert

Larson, Jr., who put a great deal of effort into this work. Some of the

many others include Britto Rajkumar, Robert Vandeberg, Robert Florom, Alex

Harrell, David Van Dyke, Daisy Cheng (summer intern), and several train and

track crews.

We are indebted to John Cowan of The Fax Corp. in Danbury, Connecticut,

Ansgar Wilbrand of XzfP in Saarbrucken, Germany, and Mike Giesking of Wheel

Checkers in Denver, Colorado, for considerable background information.

Within our own lab, there have been many helpful ideas and considerable

assistance at all stages. We are especially grateful to Dale Fitting, Todd

McGuire, Christopher Fortunko, Daniel Vigliotti, and many others. Many of

the public notices appearing in the Appendix are the result of efforts by

Collier Smith.

63
APPENDIX: PUBLIC NOTICES

Our Public Information Office has disseminated several notices regarding

this work. These were used in internal newsletters as well as several

public periodicals. Some of this publicity has generated numerous inquiries

from both potential users as well as those interested in possible commercial

production.

Those public notices of which we are aware are:

1. "NBS Monthly Highlights," Feb. 1988, pp.3-4.

2. "NIST Monthly Highlights," Sept. 1989, pp. 2-3.

3. "Materials Evaluation," Sept. 1989, p. 1018.

4. "NIST Update," Jan. 22, 1990, p. 3.

5. "Sensor Technology," March 1990, pp.4-5.

6. "Sensors," March 1990, pp. 12-13.

7. "Metalworking News," April 30, 1990.

8. "NIST Research Reports," May 1990, pp. 28-29.

9. "BusinessWeek," June 4, 1990, p. 95.

10.

Frankfurter Allgemeine Zeitung . June 26, 1990.

The authors can provide copies to any interested parties.

64
BL-114A

(5-90)

U.S. DEPARTMENT OF COMMERCE

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY

BIBLIOGRAPHIC DATA SHEET

1. PUBLICATION! OB REPORT NUMBER

NISTIR 91-3967

2. PERFORMING ORGANIZATION REPORT NUMBER

PUBLICATION DATE

May 1991

4.

TITLE AND SUBTITLE

Report No. 22

TREAD CRACK DETECTION IN RAILROAD WHEELS:

AN ULTRASONIC SYSTEM USING EMATS

5.

AUTHOR(S) Raymond E. Schramm, Alfred V. Clark, Jr., Dragan V. Mitrakovic^ Yossef Cohen, Peter J. Shull,

Stephen R. Schaps

6.

PERFORMING ORGANIZATION OF JOINT OR OTHER THAN NIST, SEE INSTRUCTIONS)

U.S. DEPARTMENT OF COMMERCE

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY

BOULDER, COLORADO 80303-3328

7. CONTRACT/GRANT NUMBER

DTFR 53-89-X-00018

8. TYPE OF REPORT AND PERIOD COVERED

Final 9/85 - 12/90

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (STREET, CITY, STATE, ZIP)

U.S. Department of Transportation, Federal Radilroad Administration, Office of Research

and Development, Washington, DC 20590

10.

SUPPLEMENTARY NOTES

11.

ABSTRACT (A 200-WORD OR LESS FACTUAL SUMMARY OF MOST SIGNIFICANT INFORMATION. IF DOCUMENT INCLUDES A SIGNIFICANT BIBLIOGRAPHY OR

UTERATURE SURVEY, MENTION IT HERE.)

This is report number 22 in a series covering research performed by the National Institute

of Standards and Technology (NIST) for the Federal Railroad Administration (FRA). This

report covers a project by the Materials Reliability Division (formerly the Fracture and

Deformation Division) to develop and build an ultrasonic system to detect crack-type flaws

in the tread of railroad wheels. To achieve fully automatic operation, the sensor is built

into the rail so testing occurs as the train rolls past. Signal analysis takes place in

real time.

The ultrasonic probe is an EMAT (electromagnetic-acoustic transducer) . As configured here,

the EMAT has a small footprint, and, due to its principle of operation, it does not require

any acoustic couplant. The system operates in a pitch-catch mode. A short burst of Rayleigh

(surface) waves travels around the wheel tread, and an echo indicates a flaw's presence and

size. Testing was performed on both a short track in the NIST laboratory and the full-scale

facilities of the Transportation Test Center (TTC) in Pueblo, Colorado.

This report documents the design, construction, and testing of the system. It is also to

serve as an operational guide for the equipment being delivered to the FRA.

12.

KEY WORDS (6 TO 12 ENTRIES; ALPHABETICAL ORDER; CAPITALIZE ONLY PROPER NAMES; AND SEPARATE KEY WORDS BY SEMICOLONS)

crack; EMAT; nondestructive testing; railroad wheel; roll-by inspection; ultrasonic

13. AVAILABILITY X UNLIMITED

FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE TO NATIONAL TECHNICAL INFORMATION SERVICE (NTIS). 72

ORDER FROM SUPERINTENDENT OF DOCUMENTS, U.S. GOVERNMENT PRINTING OFFICE,

WASHINGTON, DC 20402.

15. PRICE

X ORDER FROM NATIONAL TECHNICAL INFORMATION SERVICE (NTIS), SPRINGFIELD, VA 22161.

14. NUMBER OF PRINTED PAGES

ELECTRONIC FORM

u.S. GOVERNMENT PRINTING OFFICE: 199! - 575-668/45108
. ...

1H