UT Book - Articles PDF
UT Book - Articles PDF
UT Book - Articles PDF
IN
RAILWAYS
PUBLISHED, 2008
BY
METALLURGICAL & CHEMICAL
DIRECTORATE
COMPILED BY
EDITED BY
INTRODUCTION
Ultrasonic, the science of using ultra high frequency sound waves for inspection of metal pieces or components
was developed independently by both Great Britain and Germany during Second World War It was used to
detect defects in steel ingots and billets in order to reduce the waste in steel. The information on the development
of ultrasonic testing was published immediately after the war, and it became apparent on the Railways that the
new method gave a hope of detecting the dangerous crack which sometimes developed wheel seat under the
wheel hub in railway axles. In 1947 the use of ultrasonic testing for carriage axle was introduced on Railways in
Great Britain.
The testing of axles was the first major railway application of ultrasonic because the type of flaw to which
axles are most susceptible to is the fatigue flaw commencing a short way inside the press fitted wheel and thus
completely invisible. There is in fact no other way known of detecting these flaws without removing the wheels.
In Indian Railways, the ultrasonic testing of axles has been introduced sometimes in mid 50s as a tool for
preventive maintenance to ensure safety in running of trains.
Subsequently, the ultrasonic testing of Rails and Rail welds was also introduced to Indian Railways in early
60s so as to ensure safety and reliability of the permanent way. The ultrasonic flaw detection gradually emerged
as one of the most powerful tools for preventive maintenance because of its easy adaptability, versatility and
sensitivity. During this period, a large number of testing procedures, specifications, guidelines, criteria etc. have
been prepared based on experience.
This technique has also been extended through Alumino Thermic (AT) Weld, Flash Butt (FB) Weld, Gas
Pressure (GB) Weld, Switch Expansion Joints (SEJ) and Points & Crossings.
RDSO, Lucknow started a Non Destructive Training Centre in November 1969 with the approval of
Railway Board. This Training Centre now organizes various courses on ultrasonic testing of axles and rails
through out the year. The Courses are Regular Course for Supervisors of four week duration, Refresher course
of one week duration for supervisors and Appreciation Course of two days for Officers. More than 7000
Personnel have been trained so far all over the Indian Railways. The Supervisors of Chemical & Metallurgical
Staff, Mechanical Department Staff and Engineering Staff are given training in Regular Course. Successful
candidates are issued certificate valid for three years for authorization of Testing Axles and Wheels, Rails and
Rail Welds. After three years they have to come for one week Refresher Course.
Other than Training, the NDT Lab, of M&C Directorate is preparing standard, testing procedure for Axles,
Wheels, Rails, Rail Welds, Crank Shaft, Equalizer Beam etc. For trials these are issued in the form of a USFD
Manual. For other items codes of procedure are issued. More than 315 Code of Procedure have been made by
the NDT Section of M&C Directorate and issued to Railways according to their need. The code of procedure
is the standardization of ultrasonic testing of the axles, wheels and other components as per their drawings. It
helps the operator to test the components. The position of desired echos is shown in the code of procedure. The
valid Trained Supervisors are testing the components ultrasonically according to these Code of Procedure.
The NDT Lab also finds out the requirement of NDT equipments for railways, does technical study and
makes technical specification for these equipments. They also develop indigenous equipments and sources as
per those specifications, so that correct equipments are also made available to Indian Railways.
Based on the above knowledge and experience, it has been decided to assimilate the entire information and
present in the form of a book to guide the ultrasonic personnel in testing, interpretation and taking decisions. The
manuals, code of procedure and specifications mentioned in the book are mandatory during testing of axles and
rails but from time to time the modifications and alterations are to be followed. This book cannot be treated as a
legal document for this purpose and is intended to serve as assistance in clearing the doubts & instill basic
concepts in the personnel engaged in Ultrasonic testing in Railways.
CONTENTS
From To
6 Emerging Techniques 72 81
7 Calibration Blocks 82 86
10 Appendices 93 129
NON DESTRUCTIVE TESTING OF MATERIALS
CHAPTER 1
NON DESTRUCTIVE TESTING OF MATERIALS
With the growth in technology demanding the ultimate from materials with increased awareness of safety
and reliability of engineering components, Non-destructive Testing is emerging as a promising interdisciplinary
science.
The field is so versatile that it is proving to be most powerful tool for quality assurance of all industries and
frontier technology areas like atomic energy, space, aeronautics, defense, warships etc.
For the Railways, the constantly increasing pressure for a safer, economic, speedier and efficient
transportation, the structural integrity of the components has assumed great importance which in turn calls for
extensive utilization of the Non-destructive techniques to ensure the component quality.
Human perception is based primarily on sight, sound, and touch. This assessment process applied to
materials is the subject of Non-destructive Testing.
The connotation e.g. NDT, NDI, NDE etc. have been used to designate Non-destructive Testing and can
be defined as the Discipline of science which deals with the detection of flaw and its characterization without
impairing the serviceability of the component.
NDT involves subjecting the material to specific physical characteristic, processing the response obtained
to a useful from and interpreting the same for flaw detection and characterization.
In effect, it is the differential behavior of the material under test at sound and unsound zone which manifests
itself in the form of a response. The physical characteristics employed may be acoustics, electrical conductivity,
thermal conductivity, radiation absorption, magnetic permeability etc.
The modification in the applied energy may be attenuation, reflection, diffraction, velocity change, amplitude
variation and such other positive and observable changes in the energy applied. These observations provide
valuable information to assess the structural integrity of the part under test.
In a nutshell, material is tested without destroying them and without affecting their serviceability. As the
material is not destroyed, this method is utilized for manufacturing control for product quality and consistency
by making it possible to check 100% components. NDT is used as condition monitoring /preventive maintenance
method to test the component during service at a regular interval of time so that it can be withdrawn from
service before its failure.
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ULTRASONICS IN RAILWAYS
Ultrasonic testing
Figure 1 : Different NDT Methods
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NON DESTRUCTIVE TESTING OF MATERIALS
a) VISUAL INSPECTION
Visual examination is the most widely used among all the NDT techniques. Even though a component is to
be inspected using other NDT methods, a good visual inspection should be carried out first.
A simple visual test can reveal gross surface defects thus leading to an immediate rejection of the component
and consequently saving much time and money. It is often necessary to examine for the presence of finer
defects. For this purpose, visual methods have been developed to a high degree of precision.
The basic procedure used in Visual NDT involves illumination of test specimen with light. The specimen is
then examined with eye or by light sensitive devices.
The equipment required for visual inspection is very simple but adequate illumination is absolutely essential.
The surface should be cleaned before testing.
THE EYE
The human eye is the most valuable tool for visual examination as it has excellent perception. For visual
inspection adequate lighting, that is, 800-1000 lux is of prime importance.
It can reveal the following information: a)The presence or absence of oxide film or corrosive product on
the surface, b)The presence or absence of surface cracks ,c) general condition of the component, d) The surface
porosity, contour of the weld beads e) Sharp notches, misalignment etc.
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ULTRASONICS IN RAILWAYS
The developer acts like a blotter, drawing the penetrant out of the defect. After a short time, indications
appear in the developer which are wider than the defect , therefore, can be seen directly or under ultraviolet
light due to the enhancement of the contrast between the penetrant and the developer.
To start with ,surface of the component is cleaned and dried. as presence of grease or paint will hinder the
test. Penetrant is applied to the component and allowed to act for a brief period. Excess penetrant is completely
removed from the surface. Developer is applied and dried off.
Lastly surface inspection is done for indication of defects.
The colour of the liquid penetrant as a rule is red with white developer so that they provide good contrast
against the developer. Some liquid penetrant contains fluorescent material which glows under ultraviolet light.
Water washable penetrant contains an emulsifier which allows surface penetrant to be removed using
water. Solvent removable penetrant can only be removed fully from the surface by means of an appropriate
organic solvent
As it has been mentioned already, developer colour is white to give a good contrast with red. penetrant. It
may be dry, water based or non water based developer.
The following pictures describes Dye Penetrant Testing.
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NON DESTRUCTIVE TESTING OF MATERIALS
The effectiveness of the test depends upon the magnitude of the leakage field which is influenced by the
following functions.
i) Intensity of he magnetizing current
ii) Permeability of the material
iii) Shape of the object under test
iv) The characterization of the flaw depends upon shape, size. location and orientation.
MAGNETISING TECHNIQUES.
The essential requirement for this test is the application of magnetic field (flux flow) of adequate intensity
along a known direction in the component. There are various techniques available for magnetizing a component.
i) Magnetization using a magnet.
ii) Magnetization using an electromagnet.
iii} Contact current flow method
iv) Coil magnetization
v) Induced current flow
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ULTRASONICS IN RAILWAYS
Here we will discuss in detail about coil magnetization. This is of two types
a) Circular magnetization
b) Longitudinal magnetization
Circular magnetization occurs when electric current is passed through a straight conductor creating a
circular magnetic field around the conductor (see Figure 4a).
Longitudinal magnetization occurs when electric current is passed through a coil of one or more turns, a
magnetic field is established within the coil (see Figure 4b).
To form an indication, the magnetic field must approach discontinuity at an angle great enough to cause the
magnetic field to leave the part and return after bridging the discontinuity. Best results occur when the intersection
is 90 degrees to the magnetic field lines.
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NON DESTRUCTIVE TESTING OF MATERIALS
Magnetic particle should be applied while the magnetizing field is present or while the current is flowing
through the casting or forging. It is applied by dipping or spraying. Frequent agitation of dye must be carried out.
Application of dry powder should be such that it settles gently in a fine dispersion on the surface of casting/
forging.
Dry powder is very sensitive towards sub surface and tiny flaws.
Magnetic particles are supplied in a wet suspension such as water or oil. The wet magnetic particle testing
method is generally more useful than the dry because the suspension provides the particles with more mobility
and makes it possible for smaller particles to be used since dust and adherence to surface contamination is
reduced or eliminated. The wet method also makes it easy to apply the particles uniformly to a relatively large
area.
Both visible and fluorescent particles are available. Most nonfluorescent particles are ferromagnetic iron
oxides, which are either black or brown in color. Fluorescent particles are coated with pigments that fluoresce
when exposed to ultraviolet light.
Carrier solutions can be water or oil-based. Water-based carriers form quicker indications, are generally
less expensive, present little or no fire hazard, give off no petrochemical fumes, and are easier to clean from the
part. Water-based solutions are usually formulated with a corrosion inhibitor to offer some corrosion protection.
However, oil-based carrier solutions offer superior corrosion and hydrogen embitterment protection to those
materials that are prone to attack by these mechanisms
The following pictures describes magnetic particle testing.
Figure 5
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ULTRASONICS IN RAILWAYS
d) RADIOGRAPHY
X Rays and gamma rays form a part of the electromagnetic spectrum of radiations. Because of their
extremely small wavelengths, these radiations posses certain characteristics which are highly suitable for detection
of unsoundness in any material. The wave lengths of X-Rays range from 2 - 0.005A (1 A = 10-10 m) whereas
that of gamma rays range is 0.5 - 0.001. A
In order to examine an object it is irradiated with X-rays or gamma radiation. The radiation will be absorbed
in the object to varying degree depending upon the thickness of the object, the composition of the material and
the wave length of the radiation.
In this way while passing through a homogeneous solid they modify there intensity as penetration proceeds.
The intensity of the rays after passing through a test specimen is measured either on photographic film or on a
fluorescent screen
If a flaw in the nature of a void is present there is less absorption of the rays with the result that a dark area
is recorded on the photographic film or light area on a fluorescent screen. It thus gives a permanent film record
of defects.
IMAGE QUALITY INDICATIOR:
They are used to measure the ability of the radiographic image to show small details. The devices are also
called penetrameter and this property of judging the finer details is termed as sensitivity .It is defined as
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NON DESTRUCTIVE TESTING OF MATERIALS
IIW ,International Institute of welding has made specimen radiographs covering all types of weld defects.
The radiographs are given colors- black, blue, green, yellow and red, depending upon the severity of defect It is
in ascending order as black color is given for free of defect radiograph.. Generally rail material is accepted as
Blue standard .Casting radiographs are evaluated as per ASTM E 446.
A picture of radiographic film is shown below.
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ULTRASONICS IN RAILWAYS
f) ULTRASONIC TESTING
A series of ultrasonic waves each lasting for a few micro-seconds are introduces in the material under test
through a coupling medium. These pulses propagate in the material in a very narrow beam until they strike an
interface such as the opposite surface of the test object or an internal defect.
The pulses are entirely or partly reflected back to the transmitter, which now functions as a receiver. The
receiving probe converts the ultrasonic waves to the electrical energy, which is amplified and displayed on a
CRT in such a manner as to indicate the time difference between the transmitted pulses and reflected pulses.
The horizontal scale of CRT is calibrated in terms of distance, hence position of flaw peak on horizontal
scale tells the location of the flaw. The vertical scale of CRT is calibrated with a standard test piece having
artificial flaws of known size, hence the height of the flaw peak tells about the size of the flaw.
The popularity of ultrasonic testing is increasing day by day.
1. High Sensitivity. Allowing very small imperfections to be detected
2. Good penetration power. Allowing the inspection of thick sections
3. Accurate determination of imperfection position and estimation of imperfection severity.
4. Fast response time. Permitting high speed in manual and automated testing.
5. One surface access. Access is required to only one surface of the product being inspected.
It has been discussed in detail in subsequent chapters.
No single NDT method will work for all flaw detection or measurement applications. Each of the methods
has advantages and disadvantages when compared to other methods. The table below summarizes the scientific
principles, common uses and the advantages and disadvantages for some of the most often used NDT methods.
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NON DESTRUCTIVE TESTING OF MATERIALS
Scientific Principles
Penetrant solution is A magnetic field is High frequency sound Alternating electrical X-rays are used to
applied to the surface of a established in a waves are sent into a current is passed through produce images of objects
precleaned component. component made from material by use of a a coil producing a using film or other
The liquid is pulled into ferromagnetic material. transducer. The sound magnetic field. When the detector that is sensitive
surface-breaking defects The magnetic lines of waves travel through the coil is placed near a to radiation. The test
by capillary action. force travel through the material and are received conductive material, the object is placed between
Excess penetrant material material, and exit and by the same transducer or changing magnetic field the radiation source and
is carefully cleaned from reenter the material at the a second transducer. The induces current flow in detector. The thickness
the surface. A developer poles. Defects such as amount of energy the material. These and the density of the
is applied to pull the crack or voids cannot transmitted or received currents travel in closed material that X-rays must
trapped penetrant back to support as much flux, and and the time the energy is loops and are called eddy penetrate affects the
the surface where it is force some of the flux received are analyzed to currents. Eddy currents amount of radiation
spread out and forms an outside of the part. determine the presence of produce their own reaching the detector.
indication. The indication Magnetic particles flaws. Changes in magnetic field that can be This variation in radiation
is much easier to see than distributed over the material thickness, and measured and used to find produces an image on the
the actual defect. component will be changes in material flaws and characterize detector that often shows
attracted to areas of flux properties can also be conductivity, internal features of the
leakage and produce a measured. permeability, and test object.
visible indication. dimensional features.
Main Uses
Used to locate cracks, Used to inspect Used to locate surface Used to detect surface Used to inspect almost
porosity, and other ferromagnetic materials and subsurface defects in and near-surface flaws in any material for surface
defects that break the (those that can be many materials including conductive materials, and subsurface defects.
surface of a material and magnetized) for defects metals, plastics, and such as the metals. Eddy X-rays can also be used
have enough volume to that result in a transition wood. Ultrasonic current inspection is also to locates and measures
trap and hold the in the magnetic inspection is also used to used to sort materials internal features, confirm
penetrant material. Liquid permeability of a measure the thickness of based on electrical the location of hidden
penetrant testing is used material. Magnetic materials and otherwise conductivity and parts in an assembly, and
to inspect large areas very particle inspection can characterize properties of magnetic permeability, to measure thickness of
efficiently and will work detect surface and near material based on sound and measures the materials.
on most nonporous surface defects. velocity and attenuation thickness of thin sheets of
materials. measurements. metal and nonconductive
coatings such as paint.
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ULTRASONICS IN RAILWAYS
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NON DESTRUCTIVE TESTING OF MATERIALS
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CHAPTER 2
ULTRASONIC : BASIC FUNDAMENTAL
Sound waves move a discrete volume of the material as they pass through a test specimen. This mechanical
movement occurs about the materials neutral position and is most commonly described by the number of
cycles about the neutral position per second.
The number of cycles per second, or frequency, of
sound waves is measured in Hertz (Hz) and can be divided
into three discrete ranges. Sound with a frequency below
approximately 10 Hz is known as subsonic and is
inaudible. Likewise, sound with a frequency above 20,000
Hz is known as ultrasonic and is also inaudible.
Assuming that the test material through which sound
passes has not been stressed beyond its elastic limit, the
material can be modeled as a system of discrete masses
connected in a grid-like manner to adjacent masses with
elastic springs. This system is depicted in figure 1.
If all of the masses on the left side of the model are
excited at the same time with the same force to the right,
then all of the particles in the first plane are forced to
oscillate to the right by the same amount. Figure 1 : Model of an elastic material.
This oscillation of the first plane of masses changes the length of the spring between the first and second
plane. This change in spring length forces the second plane of masses to also oscillate. After the second plane
has begun oscillating, forces are induced in the third plane and so on. These oscillations, and the resulting
transfer of forces to adjacent masses, result in a regular movement of each particle about its neutral position
with respect to the movement of the adjacent masses.
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ULTRASONIC : BASIC FUNDAMENTAL
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ULTRASONICS IN RAILWAYS
VELOCITY
If V is wave velocity, n is frequency and is wavelength.
Then, V= n (1)
The equation is valid for all kinds of waves (longitudinal and shear).
Usually a defect which can be detected using a particular frequency is of the order of half the wavelength
in that medium It is noted that velocity is a material property and remains constant. So, as n increases,
decreases. Greater the frequency, smaller flaw detection can be done.
For example, the commonly used frequency 2MHz, in the case of longitudinal wave in steel corresponds to
a wavelength of approximately 3mm. This gives an idea of the dimension of a flaw which can be detected
reliably using this frequency.
For longitudinal and shear waves, respectively, the following relationships relate the elastic material constants
to the speed of sound in the material:
where VL is velocity of longitudinal wave , VS is velocity of shear wave, VSUR is velocity of surface wave,
E is Youngs modulus of elasticity, G is modulus of rigidity, is Poisons ratio and is density of material.
WAVELENGTH
The following picture shows longitudinal waves having different wavelengths. The more the wavelength,
the less the capability of detection of flaw. It has already been explained in Eq.1
4. ACOUSTIC IMPEDENCE
While performing ultrasonic testing, it is important to
understand how effectively ultrasonic waves pass from one
medium to another. Generally, when an ultrasonic wave is passed
from one medium to another, some energy is reflected and the
remaining energy is transmitted. The factor that describes this
relationship is referred to as acoustical impedance.
Z = V kg/mm2
where
Z = acoustical impedance
= density
V = velocity of sound . Figure 3 : Different Wavelengths
The greater the difference in impedance at a boundary, the greater the reflection that will occur,
and therefore, the smaller the amount of energy that will be transferred.
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ULTRASONIC : BASIC FUNDAMENTAL
For reference, air has low acoustical impedance, water has higher impedance than air, and steel has higher
impedance than water.. Almost 100% of the ultrasonic energy will be reflected when passing ultrasonic waves
from air to a solid such as steel.
NORMAL INCIDENSE
Ultrasonic beam refraction and mode conversion is comparable to light as it passes from one medium to
another The figure below depicts an ultrasonic transducer that transmits an ultrasonic wave through water into
a block of steel. Because the direction of the ultrasonic wave is at a 90 degree angle with the surface of the steel
block, no change in direction of propagation of ultrasonic beam.
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ULTRASONICS IN RAILWAYS
ANGULAR INCIDENSE
As the angle of the ultrasonic transducer is altered, refraction and mode conversion occur. In the figure
below, the ultrasonic transducer has been rotated 5 degrees. The longitudinal wave from the transducer is
converted into two modes, longitudinal and shear, and both wave modes are refracted.
Notice that the waves are refracted at different angles. In this example, the L-wave is approximately four
times the transducer angle and the S-wave is just over two times the transducer angle. Angles that create two
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ULTRASONIC : BASIC FUNDAMENTAL
wave modes are not appropriate because they cause the ultrasonic
transducer to receive multiple echoes, and it is difficult to analyze
the data.
Refraction and mode conversion occur because of the
change in L-wave velocity as it passes the boundary from one
medium to another. The higher the difference in the velocity of
sounds between two materials, the larger the resulting angle of
refraction.
L-waves and S-waves have different angles of refraction
because they have dissimilar velocities within the same material.
As the angle of
the ultrasonic
t r a n s d u c e r
continues to
increase, L-waves
move closer to the
surface of the Figure 6 : Angular Incidense
component under
test. The angle at which the L-wave is parallel with the surface of
the component is referred to as the first critical angle. Only one
wave mode is echoed back to the transducer, making it easy to
interpret the data.
As the angle of the ultrasonic transducer continues to increase,
S-waves move closer to the surface of the component. The angle at
which the S-wave is parallel with the surface of the component is
referred to as the second critical angle. It can be appreciated that
Figure 7 : First Critical Angle between first and second critical angles only shear mode exits in
component.
SNELLS LAW
L-wave and S-wave reflection and refraction angles are calculated using Snells Law. Snells Law also can
be used to determine the critical angles for any combination of materials.
Where:
I = incident angle from normal of beam in the wedge or liquid
R = angle of the reflected or refracted beam in the component
VI = velocity of incident beam in the liquid or wedge
VR = velocity of reflected or refracted beam in the component
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ULTRASONICS IN RAILWAYS
Example :
Let us suppose :
Medium 1 is Perspex and medium2 is steel
Vper= 2.73 x 106 mm/sec.
Vstl =5.9 x 106mm/ sec. For L wave.
Vstl =3.23 x 106 mm/ sec. For S- wave.
Let angle of incidence of longitudinal wave is 20
Refracted longitudinal wave will make an angle 47 36 with normal. Refracted shear wave will make an
angle 47 36 with normal .
In the same way it can be seen first critical angle is 27.6 for steel & 22.6 for aluminum. The second
critical angle is 57.7 for steel & 63 for aluminum.
Since the cutting of crystals for generating the transverse wave to the specimen is difficult, the phenomenon
of mode conversion, is used in practice in the design of transverse and surface wave probes, using a Perspex
block between crystal and specimen.
ANGLUR INCIDENCE
Let us consider two media as steel and air. Since a negligible amount of energy leaves the steel because of
the extreme mis-match to air, the reflection must be total.
As we have seen earlier in refraction phenomena, two reflected beams exist in this case also. One beam
consists of longitudinal waves and the second of shear (transverse) waves. At large glancing angles of incidence,
the conversion to shear waves is almost total. In practical testing this condition frequently occurs as a result of
beam spread and produces subsidiary indications.
The greatest value a shear wave can assume is 33 degree when angle of refection for long. wave = 90
degree i.e. when the incident beam grazes the surface of specimen.
9. TRANSDUCER OR PROBE
Transducers are used in a wide variety of applications. By definition, transducers convert energy from
one form to another. In the case of ultrasonic testing, electrical energy is converted to ultrasonic energy (pressure
energy).
Ultrasonic transducers can generally be classified in 6 categories: piezoelectric, electromagnetic,
electrostatic, magnetostrictive, optical (e.g., laser), and miscellaneous. For the majority of ultrasonic testing
applications, the piezoelectric transducer is the most suitable.
PIEZOELECTRIC EFFECT
Piezoelectricity (pressure electricity) is a property of certain crystals, including quartz. As the name indicates,
electricity can be developed in one of these crystals by applying a pressure. Further, the reverse is also true:
When an electric field is applied, the crystal rapidly changes shape and, therefore, induces a pressure.
This piezoelectric effect is illustrated in figures 8ad. Figures 8a and 8b illustrate the direct piezoelectric
effect where an applied stress induces electric charges on each face. Conversely, figures 8c and 8d illustrate the
opposite piezoelectric effect where an applied electric field induces a mechanical deformation.
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ULTRASONIC : BASIC FUNDAMENTAL
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ULTRASONICS IN RAILWAYS
as possible, an impedance matching is placed between the active element and the face of the transducer.
Optimal impedance matching is achieved by sizing the matching layer so that its thickness is 1/4 of the
desired wavelength. This keeps waves that were reflected within the matching layer in phase when they exit the
layer (as illustrated in the image to the right).
For contact transducers, the matching layer is made from a material that has an acoustical impedance
between the active element and steel. Immersion transducers have a matching layer with an acoustical impedance
between the active element and water. Contact transducers also incorporate a wear plate to protect the matching
layer and active element from scratching.
The backing material supporting the crystal has a great influence on the damping characteristics of a
transducer. Using a backing material with an impedance similar to that of the active element will produce the
most effective damping.
Such a transducer will have a wider bandwidth resulting in higher sensitivity. As the mismatch in impedance
between the active element and the backing material increases, material penetration increases but transducer
sensitivity is reduced.
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ULTRASONIC : BASIC FUNDAMENTAL
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ULTRASONICS IN RAILWAYS
longitudinal waves from an angle beam transducer as shear waves are also present and can make signal
interpretation difficult.
Angle probes are of two types
i) Low angle probe
ii) High angle probe
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ULTRASONIC : BASIC FUNDAMENTAL
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ULTRASONICS IN RAILWAYS
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ULTRASONIC : BASIC FUNDAMENTAL
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ULTRASONICS IN RAILWAYS
TIME BASE
The time base circuit is required to provide a linear traverse from left to right across the cathode ray tube.
On this horizontal sweep is ultimately displayed in a vertical plane, the transmitter pulse and the various
reflected echoes in succession.
The time base circuit must be capable of generating sweep times which are variable, either continuously
or in steps, to cover the range from the minimum to the maximum for depth of material to be examined.
PULSE GENERATOR
This may be regarded as the prime mover in the sequence of events loading to the visual presentation on
the cathode ray tube screen. The initiating pulse serves a dual function.
In the first place, it is used to trigger the time-base circuit causing the spot to commence its extrusion across
the cathode ray tube face.
In the second place it triggers the transmitter value causing a large pulse of energy to be delivered to the
piezoelectric crystal.
The frequency at which this triggering action takes place is the pulse repetition frequency which ranges
from 50-1000 pulses (cycles) per second depending upon particular instrument..
A delay circuit may be introduced between the generator and the time-base to delay the start of the later
when the earlier part of the trace does not contain any useful information.
DISPLAY UNIT
In the diagram, a cathode-ray tube is shown as the display device and such tubes give a bright trace on a
fluorescent screen.
PULSE TRANSMITTER
In addition to operating the tube trace, the pulse generator also triggers the transmitter driver. It performs
this duty a short time after the spot starts to move across the face of the cathode ray tube.
This pulse ensures that a higher voltage pulse is delivered to the transmitter probe. This short pulse or
burst of ultrasonic is communicated to the object under test. But the same moment as the transducer is excited
some energy is communicated to the receiver. This is the basis of initial signal.
RECEIVER AMPLIFIER
The receiver amplifier accepts the signals from the receiving crystal and amplifies them suitably for display
on the cathode ray tube. A gain of between 10,000 and 1, 00,000 times is required, the maximum requirements
being dictated only by limitations of design factors, such as valve noise and stability.
It is seen that pulse is passed through the amplifier and fed to the Y plates of the cathode-ray tube after the
light spot has started to move across the tube in compliance with the time base voltage.
Voltage applied to Y plate deflects the light spot on a direction at right angles to that governed by the X
plates. In consequence, the pulse pulls the light spot out of its normal path and causes a peak of blip to appear
on the trace.
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ULTRASONIC : BASIC FUNDAMENTAL
DECIBEL SCALE
The decibel scale is an indication of the ratio between two conditions of the same dimension and is extensively
used in electronics. The fundamental decibel is given by the following equation where I is the measured intensity.
If two intensities, input and output, are I1 and I2 then,
dB= 10 log10 I1/I2 (9)
The intensity (I) is a square function of the voltage (V) and the decibel relationship could also be written as:
dB = 10 log10 ( V1/V2 )2 (10)
which in turn translates to: dB = 20 log10 ( V1/V2 ) (11)
Accordingly, a reduction in voltage of one half (i.e., one half the signal strength) corresponds to a drop of
approximately 6 dB.
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ULTRASONICS IN RAILWAYS
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ULTRASONIC : BASIC FUNDAMENTAL
Figure 20: Influence of Defect Size on Ultrasonic Signal Angle Beam Testing by Pulse Echo Technique
Figure 18 illustrates shadow effects. In this scan, the presence of the smaller defect is masked by the
larger defect, which shields it from the ultrasonic signal.
Figure 19 illustrates the effect of defect orientation. Although this figure indicates that no signal would be
detected, this really is not the case. Rather, a much reduced signal would actually be detected as a result of
scattering of the beam at the defect.
Figure 20 illustrates the influence of defect size.
As can be seen, with all else equivalent (for illustrative
purposes, the two defects have been shown at slightly
different locations here), a larger defect will reflect
more ultrasonic energy, yielding greater amplitude.
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ULTRASONICS IN RAILWAYS
32
ULTRASONIC : BASIC FUNDAMENTAL
transducer. This situation can occur in many types of welds, in structural metal parts, and in many other critical
components. An angle beam assembly directs sound energy into the test piece at a selected angle.
A variety of specific beam angles and probe positions are used to accommodate different part geometries
and flaw types. In the case of angled discontinuities, a properly selected angle beam assembly can direct sound
at a favorable angle for reflection back to the transducer.
To use testing, the operator must measure the distance to a reflector (sound path distance) from the
ultrasonic test data. As the transducer angle is known, the location of a reflector can be estimated.
PITCH-CATCH TECHNIQUE
The pitch-catch technique is an application of ultrasonic testing where the ultrasonic beam follows a somewhat
complex path (i.e., the beam is reflected one or more times before reaching the receiver). The two broad
categories of pitch-catch techniques are direct and indirect.
For direct pitch-catch, the receiver is placed where the reflected beam is expected if there are no defects.
The presence of a defect is found if the signal is not detected where it is expected or if the signal strength is
reduced.
Conversely, for the indirect pitch-catch technique, the receiver is placed where the reflected beam is
expected if a defect does exist. Figures 23 and 24 illustrate the application of the direct and indirect pitch-catch
techniques, respectively.
Typically, the direct pitch-catch technique is less prone to error caused by defect orientation and other
defect characteristics. On the other hand, the indirect pitch-catch technique is generally faster but may miss
some defects because of defect orientation. Both direct and indirect techniques may be used with the transmitter
and receiver on the same side or on opposing sides of a test specimen.
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ULTRASONICS IN RAILWAYS
(a) (b)
34
ULTRASONIC : BASIC FUNDAMENTAL
Figures 25a and 25b conceptually illustrate how a DAC curve would be generated for an angle beam
transducer. In figure 25a, a side-drilled hole is shown in a test block that can be scanned with four different
scanning patterns. Note that one could double the number of points on the DAC curve by using a second
equivalent side-drilled hole at a different depth. When the echo signals are plotted together, the DAC curve
shown in figure 25b results. This curve is referred to as 100 percent DAC. This means that for an equivalent
defect in the test specimen, the echo signal will fall on this line. Smaller or larger defects in the test specimen
will lie below or above the 100 percent DAC curve, respectively. The most accurate way to assess these
defects is to repeat the DAC curve generation with a series of diameter holes. The result will be a series of
curves that should allow for more accurate defect assessment.
IMMERSION TESTING
Immersion testing is carried out mainly for laboratory and for large installations for a large number of
components. In immersion testing both the probe and component are immersed in water. The ultrasonic beam is
directed into water either as longitudinal or transverse wave. Immersion testing has the following advantages:
1. Uniform couplant conditions are obtained and
2. Longitudinal and transverse waves can be generated with the same probe simply by changing the inclination
of the probe.
The ultrasonic beam is directed through the water into the test specimen either as a normal beam or an
angle beam.
35
ULTRASONICS IN RAILWAYS
actually requires the operator to generate a beam profile plot with a beam calibration block containing several
holes at different depths before sizing any defects. The beam profile plot is generated as follows:
1. Locate a hole and maximize the echo amplitude (location O).
2. Move the probe forward until the echo is reduced by 20 dB and note the location.
3. Move the probe backward from location O until the echo is reduced by 20 dB and note
4. the location.
5. Repeat steps 1 through 3 for different hole depths and sizes.
With this information, a beam profile plot is generated. The following procedure is used to size actual
defects using the 20-dB drop technique:
1. Locate the flaw.
2. Maximize the echo noting the amplitude and location.
3. Move the probe forward and backward noting the 20-dB drop positions.
4. Use the beam profile plot to determine the depth and size of the defect.
AMPLITUDE TECHNIQUES
A) THE COMPARATOR BLOCK TECHNIQUE
The use of a comparator block is the most straightforward, easy, and possibly most accurate technique for
sizing reflectors. The technique consists of comparing the echo from an artificial target in a fabricated test block
to echoes found in the component. The test block must be of similar material to the test specimen. In addition,
the artificial target must be in approximately the same location (referenced to the test surface) as the actual
defect. This requires that the test block be fabricated with prior knowledge of likely locations for defects.
For example, the discontinuity in component reflects the sound waves the same as a circular disk having a
diameter of 4 mm. Due to the fact that we can only assess the sound reflected from the discontinuities we must
of course not equate the diameter of 4 mm with the true size of the discontinuity. We therefore refer to them
as an equivalent disk-shaped reflector or as equivalent reflector size (ERS) . The equivalent reflector
size only corresponds to the true reflector size of a discontinuity in an ideal case which is when it is circular and
exactly hit vertical to the acoustic axis.
In practice this almost never occurs which means that the true size of a discontinuity is normally larger
than the equivalent reflector size. A law for this cannot be derived because the echo height is strongly dependent
on the characteristics of the discontinuity, this means its geometry, orientation to the sound beam and the surface
quality
Scanning the discontinuity from different directions, assessing the echo shape and the behavior of the
display when moving the probe are just a few techniques which can be successfully applied.
36
DEFECTS IN RAIL AND THEIR DETECTION BY UST
CHAPTER 3
DEFECTS IN RAIL AND THEIR DETECTION BY UST
Inherent defects:
Defects such as unsatisfactory composition, harmful segregation, piping which arises at the stage of manufacture
of ingots and also seams, laps, guide marks, flakes (hair line cracks) which arises in the stage of rolling of the
rails, falls under this category. Defects in chemistry and internal defects such as segregation, inclusion etc. can
not be determined by visual examination of the fracture face and appropriate metallurgical technique should be
adopted to reveal these defects.
Pipe: Due to contraction of molten metal steel on solidification, axial cavities, continuous or discontinuous, are
formed usually towards the top portion of the ingot and sometimes extending into the ingot. Due to the solidification
characteristic of the steel, not only is there a pronounced segregation towards the core, but also the surface of
the pipe cavity is often contaminated with inclusions and oxide products. During rolling, the surfaces of the
cavities do not get welded up. If sufficient length of the cavities do not get welded up. If sufficient length of the
portion of the rolled bloom representing the top of the ingot is not cropped off, the bloom is likely to contain pipe
defects which will persist in the rolled rail, usually in the web and regions adjacent to it.
Seam: A seam can be defined as longitudinal manufacturing defect usually of small depth arising from blow
holes or subsurface cracks in the ingots or blooms which get elongated and closed but do not weld up during
rolling. These are either present as lines parallel to the direction of rolling on the as rolled surface or just below
it.
Lap: A defect appearing as a seam on the surface of forged or rolled products. It is caused by folding over of hot
steel in the form of fins, sharp corners, etc, on the surface and subsequently rolled or forged but not welded to
the surface. Laps may also arise from defective groves in rolls.
Roll/Guide mark: These are longitudinal surface defects, appearing usually as pairs parallel to the direction of
rolling and of very small depths caused by the guides in the rolling mills or certain defects in the rolls.
Flakes or hair lines cracks: These are fine internal cracks of usually small lengths. These are confined to the
interior and are therefore difficult to detect. These flakes result from the combined effects of transformation
stresses and integral pressure build-up by molecular hydrogen arising from the segregation and release of dissolved
hydrogen during cooling. The local stress thus produced, often exceeds the strength of the material causing
numerous small rupture which are called hair-line cracks.
Inclusions and flakes may give rise to transverse fissure, shelling etc. while piping and heavy segregation
leads to vertical longitudinal head split, web splits etc. Failures such as half moon breakage in the foot are often
associates with seams at the bottom of the rails.
Service defects:
Depending upon the dynamic stresses caused by vertical and dynamic loads particularly by vehicles with
wheel flats or when the vehicle runs over poorly maintained rail joints etc, normally the growth of transverse
defects may be categorised into three type-
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ULTRASONICS IN RAILWAYS
a) Normal Growth: During normal growth of transverse defect in rail, it develops over an appreciable
period of time in very gradual stages. The entire face of the transverse separation becomes smooth and well
defined.
b) Rapid Growth: The small , polished , well defined fracture is surrounded by a rough granular surface
which shows the outline of several growth rings of gradual increasing size. The fracture face given below shows
the growth rings.
c) Sudden Growth : The small polished , well defined fracture is surrounded by a rough granular surface
which shows the out line of one or two growth rings. The distance between the rings will increase directly with
the rate of growth.
Transverse Fissures:
The transverse fissures is a progressive cross wise fracture starting from a centre or nucleus inside the
head of the rail, then spreading outward substantially at right angles to the running surface of rail. It originate
due to an imperfection in steel, such as shatter crack, a minute inclusion or blow holes. Growth is normally slow
to size of 20 - 25% then more rapid.
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DEFECTS IN RAIL AND THEIR DETECTION BY UST
Compound Fissure: The compound fissure is a progressive fracture in the head of the rail generally staring as
horizontal separation which turns up or down direction substantially at right angles to the running surface. It
originate from an internal longitudinal seam, segregation or inclusion. Transverse growth is normally slow to
size of 30 to 35 %.
Horizontal split Head: In horizontal split head , separation along a seam spreads horizontally through the
head, parallel to running surface. The origin is an internal longitudinal seam segregation, or inclusion. Growth is
usually rapid for the length of internal longitudinal separation.
A shear break is a longitudinal separation of the rail head as the material is torn off by mechanical force. A
shear break is not associated with inherent condition. Breakage is usually found sudden.
39
ULTRASONICS IN RAILWAYS
Split Web:
The split web is a progressive fracture through the web, which develops in a
longitudinal or transverse direction, or both. The origin is a seam in the web or
damage to the web. Split webs sometimes develop at
locations where heat numbers are stamped into web or
the web has experienced mechanical damage. Growth
is usually rapid after the crack extends through web,
and is accelerated by eccentric or heavy loading.
Piped Rail:
General appearance of
It is a progressive longitudinal fracture in the web split web
of the rail, with a vertical separation or seam which opens
into a cavity. It originate by a wide longitudinal seam or cavity inside the web, which
extends vertically towards the head and base of the rail.
Piped Rail
40
DEFECTS IN RAIL AND THEIR DETECTION BY UST
Surface defects
a) Shelling:
Shelling is a surface defects which appear as dark spots irregularly placed on the gage side of the running
surface. It reveals longitudinal separation at one or several levels in the upper gage corner, with dislocation from
bleeding. If rail is turned, shelly spots will appear on the field side, with an irregular overhanging lip of metal.
Appearance is then similar to flowed rail.
b) Flaking:
Flaking is not a serious defect. Very shallow depressions with irregular edges,
occurring on the running surface near the upper gage corner. Generally will not occur more
than in from the gage corner of the rail. Horizontal hairline cracks along the running
surface.
c) Silvers:
Silvers are not a serious defects. Thin silvers on the surface of
the rail head parallel to the rail length. Darkened silvers giving an
appearance much like the vertical split head but without any spreading or crushing of the
rail head. Silvers on the side of the rail head. All silvers are generally less than 1/8 in. thick.
41
ULTRASONICS IN RAILWAYS
Procedure:
1. Calibrate the horizontal scale of the UFD for required depth range.
2. Calibrate the vertical scale using standard block having artificial flaws of known size.
3. Scan the rail using suitable transducer.
4. Compare the trace pattern with the trace pattern from standard block.
5. Follow the rejection criteria as specified in the USFD manual.
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DEFECTS IN RAIL AND THEIR DETECTION BY UST
5 FBH
12 THROUGH HOLE
25
20
40
20 25
90
APPROX. 100
1.25m LONG ALUMINIUM / WOODEN HOUSING FOR TEST PIECE HAVING TOP TABLE
WIDTH EQUAL TO RAIL HEAD WIDTH
1. The slice from rail head for sensitivity setting shall be from rail of same sectional weight which is to be tested (i.e. for testing on 60Kg/52Kg, 90R rails etc. the
sensitivity testing piece shall be from 60Kg, 52Kg, 90R rails respectively.
2. In case of machines having provision of variable shift of gauge face probes following shall be ensured:
a) Maximum shift of probe shall be limited to the extant up to which there is no loss of acoustic coupling depending on rail top profile.
b) The sensitivity setting shall be done at the shift level with which actual testing is to be carried out.
c) The shift of probe shall not be altered during testing without fresh setting at altered shift .
ALL DIMENSIONS ARE IN mm.
DRAWING IS NOT TO SCALE
43
ULTRASONICS IN RAILWAYS
44
DEFECTS IN RAIL AND THEIR DETECTION BY UST
45
ULTRASONICS IN RAILWAYS
46
DEFECTS IN WHEELS AND AXLES AND DETECTION BY UST
CHAPTER 4
DEFECTS IN WHEELS AND AXLES AND DETECTION
BY UST
WHEEL
Wheels are made up of carbon steel forgings which are subsequently heat treated and machined to subsequent
dimensions. Wheels are also manufactured by casting process. The defects in wheel may be classified in two
groups,
1. Inherent defects
2. Service defects
1. INHERENT DEFECTS
The defects encountered during steel-making , shaping and machining operations may be summarized as
unsatisfactory chemical composition, micro structure, harmful inclusion, segregation, pipe, flake, etc. which are
associated with faults in the making of steel and manufacturing into wheels.
As wheels are also manufactured by casting process, defects related to casting may appear as porosity,
blowholes, and slag inclusions etc. Improper heat treatment may lead to coarse grain structure,
Processing defect arise during machining, fabrication, handling etc. They can be summarized as deep tool
mark, dent mark arising during machining, fabrication, handling etc.
2. SERVICE DEFECTS
Defects developing in wheels during their service life due to service condition leading to failure . The
examples are written below.
Wheel shelling defect : Wheel shelling, separation of metal from wheel , is a rolling contact fatigue phenomenon
that leads to damage on the wheel tread and eventually small pieces of the wheel tread break off.
Thermal cracking defect : Thermal cracking is a process that requires elevated temperatures which is
generated during severe braking. Often, these cracks are found on wheels with heat checks and the cracks
appear to be closely related.
Sliding defect : It occurs when wheel will slide on a rail as a result of the retarding force between wheel
and brake shoe is greater than the adhesive force between wheel and rail.
Wheel Spalling defect : It occurs in service after the wheel slides on the rail and patches of martensite are
formed on the tread. In spalling, the crack network is either perpendicular or parallel to the surface.
Shattered Rim defect : This type of defect originate at the sub-surface of tread resulting in fatigue initiation
which further progresses circumferentially and when the fatigue crack gets connected with tread surface, a
chunk of metal is dislodged from tread.
Other defects in wheel can be written as sharp corner at rim edge, wheel flat, spread rim, thinning of
flange, punch mark at wheel rim etc.
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ULTRASONICS IN RAILWAYS
SHELLING
ORIGIN (I) SURFACE MARTENSITE SPOTS,
NORMALLY BY SLIP
(II) SUBSURFACE FATIGUE DUE TO
ROLLING CONTACT CAUSED BY
TANGENTIAL STRESS
48
DEFECTS IN WHEELS AND AXLES AND DETECTION BY UST
VERTICAL SPLIT
ORIGIN- INHERENT DEFECT IN INGOT
REMEDY- PROPER CROPPING OF INGOT
49
ULTRASONICS IN RAILWAYS
SHATTERED RIM
ORIGIN- INHERENT DEFECT LIKE
CLUSTER OF INCLUSIONS,
FORGING BURST, LOWER
STRENGTH.
REMEDY- CLEAN STEEL, USFD -
TREAD PROBING
THERMAL CRACKS
ORIGIN-THERMAL CRACKS
REMEDY-LOWER C%, DESIGN, DISC
BRAKE, MAINTENANCE OF BRAKE SYSTEM
THERMAL DAMAGE TO WHEEL
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DEFECTS IN WHEELS AND AXLES AND DETECTION BY UST
51
ULTRASONICS IN RAILWAYS
AXLE
Railway axles are one of the most highly stressed components of the various rolling stocks in use. The
safety and reliability of these axles are therefore of paramount importance. The following discussion is about
defects, which are observed on them.
A) STEEL MAKING:
The steels are required for manufacture of axles can be made in open hearth furnace, basic oxygen
process or a combination of these processes. The steel so manufactured is required to be of killed quality in
order to have maximum fatigue strength under condition of dynamic loading. The steel required to have a
maximum of 0.007%of nitrogen and 2ppm of hydrogen if produced by basic oxygen processes. These two
elements have the tendency to develop crack/brittleness during subsequent manufacturing operations or service.
In order to obtain the desired mechanical properties and freedom from hot shortness and cold shortness, sulphur
and phosphorous contents should not exceed 0.05%. The steel so produced are in the form of ingots which is
further worked down to obtain the final product. In order to ensure freedom from undesirable piping and harmful
segregation, sufficient discard is necessary from the ingot.
B) AXLE FORGING:
The ingots so produced are converted in the form of blooms in a blooming mill and the finished shape of the
forged axle is obtained by forging the bloom in a press or a forging hammer. The reduction ratio from ingot to
axle should not be generally less than 4:1. The forged axles are allowed to cool slowly after forging. The forged
blanks are thereafter suitably heat treated (normalized or quenched and tempered) to obtain the desirable micro
structure and mechanical properties.
During the process of manufacture of steel and also during subsequent mechanical working operations for
producing the final shape of axle, it is essential to ensure freedom from defects e.g. pipe, segregation, cracks,
flakes, laps, seam, etc. These defects are undesirable as their presence leads to failure of axles in service.
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DEFECTS IN WHEELS AND AXLES AND DETECTION BY UST
Sufficient control of heat treatment process is essential to obtain the desired mechanical property and avoid
undesirable micro structure (e.g. overheated or burnt structures).
C) MACHINING:
The forged and heat treated blocks are thereafter machined to drawing dimensions providing generally 60
included angle for lathe centres. Utmost care is essential in maintaining the specified surface finish especially on
the journals and wheel seat areas. The fillet radii at each change of section has to be a gradual transition and of
correct dimension. Sharp changes in section, tool marks, dent marks, machining marks etc. on the surface of the
axle are undesirable. The fatigue properties on the axles are highly sensitive to the surface imperfections. It is
only logical, therefore, that the handling of the machined axles also warrants due care to prevent surface damage.
53
ULTRASONICS IN RAILWAYS
BRITTLE FAILURE
54
DEFECTS IN WHEELS AND AXLES AND DETECTION BY UST
55
ULTRASONICS IN RAILWAYS
WHEEL
For detecting internal discontinuities in the rim and the hub of the wheel, ultrasonic inspection is carried out
. It shall be performed after final thermal and machining operations. The wheels are passed through Go/no Go
evaluation system of ultrasonic testing method , based on Indian Railway Specification . Recent system of
evaluation can also provide the position and severity of defects.
The rims of the wheels are checked through ultrasonic inspection to detect defects at two orientations.
AXLE
For detecting internal discontinuities in new axles the following three tests are done
1. Penetration Test
2. Discontinuity Detection Test
3. Longitudinal Discontinuity Detection Test
Penetration Test
For ascertaining the suitability or otherwise in respect of grain size of the axles this test is done. Axles with
coarse grained structure exhibits poor fracture toughness, reduced impact resistance and propensity towards
higher rate of crack growth Acceptance criteria will be as per IRS specification.
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DEFECTS IN WHEELS AND AXLES AND DETECTION BY UST
57
ULTRASONICS IN RAILWAYS
CONTROL SIGNAL
Axles of particular design are tested and echoes arising in CRT screen are noted down .One signal is
selected, for a particular scanning technique. It is called CONTROL SIGNAL. Each type of axle has its own
code of procedure. Testing is done at specified height of control echo (gain level) as mentioned in code of
procedure.
Control signal for Far end testing is generally taken from a far end fillet.
Control signal for Near End Low Angle Testing is taken from inner fillet.
Control signal for High Angle testing is generally taken from same location as in Near End Low Angle
Testing.
The Standard echoes are observed during scanning of axles. Extra echo is cause of concern as it may be
occurring from a defect.
This test is carried out to test the full axle. The probable reflectors in an axle may be as follows: end of the
axle, journal fillet, wheel seat fillet, motor bearing seat fillet, stress relief grooves etc. Additional echoes appear
due to mode conversion of sound wave.
58
DEFECTS IN WHEELS AND AXLES AND DETECTION BY UST
TRAJECTORY NO.1
A longitudinal beam propagating along the axle when strikes the fillet at an angle of 45o as shown below, the
longitudinal wave is reflected to the point diametrically opposite and having normal incidence at the boundary
due to which it retraces its path back to the probe and creates a peak on the oscillogram at a distance equivalent
to the path traveled in term of longitudinal mode. The shear wave component is very weak. The trajectory
length of the longitudinal wave under such condition can be calculated by,
T1 = L + (D + d )/2
TRAJECTORY NO.2
Considering that the ultrasonic waves propagate from the probe face in a bundle having a
solid angle depending upon the diameter of the probe used and the frequency, there would be eam having
a typical angle of incidence of 61o and hence will have another mode change as shown below. The trajectory
length will be defined by:
T2 = L + 1.82 (D + d)/2
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ULTRASONICS IN RAILWAYS
TRAJECTORY NO.3
When a longitudinal beam strikes at an angle of 85 degree, it splits up into a strong shear wave and a weak
longitudinal wave. The longitudinal wave is reflected back in its path and the reflected energy is received by the
probe to give the indication at a distance equivalent to L on the oscillogram .The shear wave reflects at an angle
of 33o and when it meets the corner R the stress relieving groove is reflected. back.
In the case of the shear wave which is reflected from a point R the total time taken is much more than that
taken by the longitudinal wave and hence a peak is displayed on the oscilogram at a trajectory length of L + 1.57
D approx. In case the relieving groove were to be absent the longitudinal and the shear wave would have
traveled further along the axle and would have appended their energy and consequently caused no peak to
appear on the oscillogram.
T3= L + 1.57D
PROBE TO BE USED: 2.5 MHz single crystal normal probe of diameter 20/25 is
generally used.
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DEFECTS IN WHEELS AND AXLES AND DETECTION BY UST
61
ULTRASONICS IN RAILWAYS
Different angles are prescribed for wheel seat and gear seat . testing . Scanning by low angle in wheel seat
and gear seat is shown respectively. Generally calibration is done for 1000 mm longitudinal wave.
PROBE TO BE USED: The angle probe used are 5, 7.5, 10, 12.5, 15, 17.5 are used. Selection of probe
angle is done based on geometry of axle.
PROBE TO BE USED:
The angle probe used are 33 and 45 Selection of probe angle is done based on geometry of axle
62
DEFECTS IN WHEELS AND AXLES AND DETECTION BY UST
63
ULTRASONICS IN RAILWAYS
and as such should not be certified to continue in service. For ascertaining the suitability or otherwise in respect
of grain size of the axles under test , the following steps may be followed by the ultrasonic test personnel.
a) Axles should be tested with 2.5 MHz probes. Absence or depleted back wall echo associated with grassy
pattern received from all the available probing positions during gain setting makes the axle suspect regarding
grain size.
b) Such axles should be further tested with 1.25 MHz probes and if the back wall echo amplitude improves
with absence or decreasing grassy pattern , the presence of coarse grained structure is confirmed. In such
case the axle should be removed from service.
However , it is also mentioned that depleted back wall echo and presence of grassy type pattern may also
be obtained from improper acoustic coupling , deep seated punch marks ,presence of concavity ,convexity in
the axle end faces and from loose contacts ,defective be checked before conforming any axle .
64
APPLICATION OF ULTRASONIC TESTING ON OTHER CRITICAL COMPONENTS
CHAPTER 5
APPLICATION OF ULTRASONIC TESTING ON OTHER CRITICAL
COMPONENTS
Application of ultrasonics for the evaluation of integrity of components such as Axles, Wheels, Rails & Rail
Welds have already been covered in earlier chapters. In this chapter emphasis has been given on characterisation
of defects and evaluation of integrity of various other critical components used in Indian Railways as mentioned
below.
a. Butt Welds of Bogie Frames.
b. Fillet Welds of Bridge Girders.
c. Armature Shafts.
d. Bearing.
BOGIE FRAMES
In past bogie frames were evaluated by
radiography for its soundness. Radiography gives
idea about the orientation of the discontinuity.
Since radiography is a costly method and
associated with health hazards, evaluation of
bogie frames have been done by switching over
to ultrasonic. The ultrasonic system of evaluation
is calibrated with help of radiographic method.
Bogie frame is a critical component, on which
whole structure of the Locomotive rests. It is
manufactured by fabrication of the plates with
help of butt welding. For welding MIG/MAG Co Co bogie
technique is being employed. There is possibility
of generation of defects in two stages, first inherent manufacturing defects in plates and other arising during
the process of welding. Such defects can be detected with help of various NDT methods.
Ultrasonic play an important role also for detection of inherent internal manufacturing defects of the
plates such as air filled laminations (loose tackiness of layers), inclusions etc. Plates are prior examined
ultrasonically with the aid of normal probe with reference to relevant standards.
Weld is considered to be week link in any assembly. The commonly occurring defects in welded joints are
porosity, slag inclusions, lack of side-wall fusion, lack of inter-run fusion, lack of root penetration, undercutting
and longitudinal or transverse cracks. Soundness of the weld is ensured by means of NDT so that it will be less
susceptible to failure.
Testing butt welds with normally (00) probes is only occasionally possible if the geometry of the specimen
is favourable. Weld defect evaluation is being done by angle beam scanning technique.
For ultrasonic examination of butt welded joints in bogie frames, normal and angular probes are used. The
angle of the probe may be 450 or 600 or 700 depending on the plate thickness.
65
ULTRASONICS IN RAILWAYS
1. Testing a Butt weld from the weld from the welded-on flange. 2. Sound paths for half and full skip distance.
66
APPLICATION OF ULTRASONIC TESTING ON OTHER CRITICAL COMPONENTS
Testing fillet welds (a) joint not penetrated (b) joints fully penetrated (K Joint)
67
ULTRASONICS IN RAILWAYS
ARMATURE SHAFT
Armature shaft is a rotor shaft in motor of the
electric locomotive. With help of this shaft power of motor
transmission occur for rotation of loco axle drive. More
stresses is generated during service. This shaft tested
ultrasonically in two stages:
1. Initial testing to detect manufacturing defects
2. Periodic testing to detect cracks generated in
service.
Initial testing to detect manufacturing defects:
The manufacture stage generated defects are
detected by this testing. After manufacturing armature
shaft is subjected to ultrasonic examination for detection of defects. These following techniques are employed
for the same:
(a) Penetration test
(b) Longitudinal discontinuity detection (Diametrical probing)
(c) Transverse discontinuity detection (with help of DAC)
The detailed procedure of testing to be adopted is followed based on relevant standard/specification.
Periodic testing to detect cracks generated in service :
When armature shaft is put into the service, transverse, fatigue cracks are generated. Such types defects
are detected with help of periodic ultrasonic testing. Following techniques are employed for detection of
cracks generated in service.
(a) Far end scanning
(b) Near end low angle scanning.
The testing is being carried out with reference to relevant standard/specification as mention in later chapter
under list of specification/code of procedure.
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APPLICATION OF ULTRASONIC TESTING ON OTHER CRITICAL COMPONENTS
BEARINGS
Bearings are considered to be one of the most critical components from safety point of view. During
service it remains under higher amount of load. Therefore it becomes extremely important to ensure the integrity
of the bearing before putting them into the service. On slide or shell bearings the bonding of the tin or lead-
bronze liner to the steel backing has to be tested. The bearing alloy has approximately the same acoustic
impedance as steel, with the result that a properly bonded boundary gives only weak echoes. The test of the
bonding is usually performed with the echo method. The bond can also be tested using the echo from the bond
and the back echo of the support.
The testing is being carried out with reference to relevant standard/specification as mention in later chapter
under list of specification/code of procedure.
Other items which can not be examined by Ultrasonic testing
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ULTRASONICS IN RAILWAYS
Above pattern depicts the ultrasonic test pattern obtained from the cast items where it is evident that the
attenuation become predominant and noise level goes high. Therefore interpretation of signals becomes more
complicated to arrive at concrete conclusion.
Evaluation of cast items are done preferably using MPI/DPI technique.
Ultrasonic Examination of Austenitic Steels:
Ultrasonic testing of in austenitic stainless steel is a much more difficult problem than ferritic steels, with
some alloys and thickness. The austenitic metal consists, in most cases, of large elongated anisotropic grains
forming a fibrous structure with symmetry around the fibre axis. There are therefore a number of basic problems
1. There is severe attenuation, particularly at high frequencies.
2. The anisotropic grain structure (dendrites) causes the ultrasonic beam to bend, particularly with shear
waves; this means that ultrasonic propagation is a function of the grain orientation.
3. The material is noisy there is a large amount of grass on the display, which can completely mask the
pulse from flaws.
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APPLICATION OF ULTRASONIC TESTING ON OTHER CRITICAL COMPONENTS
The main problem was thought at one time to be due to ultrasonic scatter.
Ultrasonic propagation depends strongly on the orientation of the ultrasonic beam to
the fibre axis.
Attenuation effects in austenitic steels are also not fully understood. The
attenuation factor increases with average grain size, but is also a function of the (grain
size)/wavelength ratio.
Austenitic steel castings produce the same difficulties as austenitic steel welds.
So, austenitic steel casting product like CMS crossing (cast manganese steel crossing)
is also not suitable for ultrasonic testing.
Evaluation of austenitic steel items (like cast manganese steel crossing, jaw
crusher plate etc.) are done preferably using DPI technique.
Cast Manganese
ULTRASONIC EXAMINATION OF NON FERROUS ITEMS
Ultrasonic examination also employed for evaluation of non ferrous items such as copper, aluminium,
brass etc. The principal of ultrasonic testing remains the same except the fact that velocity of the sound wave
varies with respect to the medium of wave propagation. The velocity of sound waves in different medium is
listed below:
VELOCITY CORRECTION
If the calibration block used for the time base calibration is a different material then that of material of the
specimen, then the masured thickness of the specimen has to be corrected for the difference in velocities in the
calibration blocks and the test specimen.
The correction is made as follows:
71
ULTRASONICS IN RAILWAYS
CHAPTER 6
EMERGENT TECHNIQUES
Many new techniques has been emerged for generating ultrasonic waves. These techniques are having
their own merits. Projects on its application to Indian Railways is in process. Indian Railways are having ample
scope in assimilating these techniques for its own advantage. Followings are some main advantage over
conventional method-
Parameter Conventional UT Advanced UT
Flaw Nature Operator Experience Signal Processing
Flaw depth Amplitude comparison with Time-of-flight (Tip Diffraction & TOFD)
reference
Record A-scan (No permanent record) Imaging (B & C-scan), Data storage
Multiple beam angles Single Probe, Single angle Multiple probes, Phased Arrays
Access Direct Contact Non-Contact (EMATs, Laser UT)
Material Property Not much information Several parameters Non-linear UT
Coverage Limited Guided waves
72
EMERGENT TECHNIQUES
B-Scan: A sectional image (B-Scan ) is a 2D view of the recorded ultrasonic data. Generally in B-scanning,
horizontal axis is taken as the scan position and vertical axis is the time base i.e ultrasound path. The axis may
also reversed depending upon the required display. The position of the displayed data is related to the encoder
positions at the moment of the acquisition. A B-Scan is a series of stacked A-Scan or wavforms.
C Scan: A C-Scan is a two dimensional view of ultrasound data which is displayed as top or plan view of the
object under test. The position of the displayed data is related to the encoder positions during acquisition.
73
ULTRASONICS IN RAILWAYS
74
EMERGENT TECHNIQUES
Characteristic of the system: The characteristic of the system i.e probe, equipment and A-Scan converter
shall be as-
For the probe- The parameter listed has greater importance for selecting a phased array probe. Probe type,
frequency and wave mode , number of elements, size of the elements, sensitivity variation of of different elements,
size of the effective transducer dimensions, delay path length, range of variation of the skewing and the incidence
angle. Angle of incidence for a zero delay time distribution or wedge angle is also important parameter. The
pictures of a linear array conventional probe & multi-element phased array probes are given below.
Besides the classical sound field and spectral characterization of conventional probe, the parameters, element
sensitivity, element separation and directivity pattern and grating lobe suppression must be recorded.
Fig. A
75
ULTRASONICS IN RAILWAYS
Figure : B
For A Scan Converter- The parameters, sample rate , resolution in bits, maximum and minimum dynamic
range, maximum pulse repletion rate of the A Scan conversion and data storage are regarded as operational
Parameters.
76
EMERGENT TECHNIQUES
77
ULTRASONICS IN RAILWAYS
78
EMERGENT TECHNIQUES
79
ULTRASONICS IN RAILWAYS
Limitations of TOFD:
1. Defects located at upper surface and inner surface are difficult to detect due to dead zone of the lateral
wave and because of the dead zone of the back-wall signal.
2. Defect interpretation and defect pattern recongnition require training and experience.
3. Defect location in a linear D-scan has some error due to TOF locus, since the time of arrival of diffracted
waves depend on defect position with respect to probes.
80
EMERGENT TECHNIQUES
81
ULTRASONICS IN RAILWAYS
CHAPTER 7
CALIBRATION BLOCKS
Calibration blocks are used to assess the performance of ultrasonic flaw detection equipment, including
transducers. They are also used to calibrate the equipment (setting up of gain, range, sweep rate, etc.) for the
examination of materials.
The blocks are supposed to be made of materials having a specified composition and heat treatment, and of
a given surface texture and geometrical form. Variation in any characteristic from block to block may lead to
different interpretation of results. It is desirable that all the calibration blocks, used anywhere in the world, have
the same general properties.
While it is not difficult to verify the dimensions and the geometry of blocks, the test for other properties
such as composition, heat treatment, and surface texture is not straightforward. These other properties cast
appreciable influence on ultrasonic velocity and attenuation.
Fortunately, these two ultrasonic parameters are desired to be nearly the same in blocks, and if these
parameters have the same values, one need not go to the extent of evaluating composition, grain size, surface
texture, etc.
82
CALIBRATION BLOCKS
i) V1 or A2 Block
Figure 1 : V1 block
The V1 block (according to BS 2704 - A2), has a thickness of exactly 25 mm and is made of low-alloyed
fine grained steel so that it can be used for nearly all types of calibration when similar steels are to be tested. The
following properties of Ultrasonic flaw detector and probe are checked
i) Linearity of Time-base ii) Linearity of amplification
iii) Resolution iv) Dead Zone
v) Penetrating Power vi) Sensitivity
vii) Angle of probe
ii) V2 or A4 Block.
For the miniature angle-beam probe one uses the considerably smaller and lighter Standard Calibration
Block, V2 block. This has, as opposed to the V1 block, two circle segments with a common center point,
however it does not have saw cuts. The required echo sequence is produced here by the alternating reflection of
the sound wave..
(a) (b)
Figure 2 : V2 Block
83
ULTRASONICS IN RAILWAYS
3. STEP GAUGE
Step gauge is used for measurement of dead zone Near surface discontinuities can be detected if dead
zone is less.
T/R (double crystal) probe has less dead zone than T+R (single crystal) probe .
84
CALIBRATION BLOCKS
Figure 5 : Transducer and Hole Location for Generating DAC Curve and Resulting DAC Curve
85
ULTRASONICS IN RAILWAYS
Figure 6 : Flat bottom holes and ecohes coming from flat bottom holes
Figure 7
86
ULTRASONICS IN RAILWAYS
CHAPTER-8
EFFECT OF ENVIROMENTAL & EXTERNAL
FACTORS ON SIGNAL HEIGHT
87
ULTRASONICS IN RAILWAYS
CHAPTER - 9
TRAINING OF PERSONNEL IN ULTRASONIC
TESTING OF RAILS AND AXLES
The Non Destructive Testing (NDT) Training Centre of RDSO was established in 1969. Since then more
than 7000 Personnel have been trained in this Centre. This training Centre is giving training to Supervisors of
Indian Railways who are engaged in ultrasonic, ultrasonic testing of Rails in Service, Alumino Thermic (AT)
Welding of Rails in Service, Switch Expansion Joints (SEJ) in Service, Flash Butt Welding of Rails etc. in
Zonal Railways and Ultrasonic Testing of Carriage, Wagon, EMU, Diesel Locomotives and Electric Locomotives
Axles and wheels in Workshops, Production Units, EMU Car Sheds, Diesel Sheds and other maintenance sheds
of Zonal Railways. This training is mandatory for doing Ultrasonic Testing. This Training Centre also giving
training to Officers of Zonal Railways and Production Units who are related with Ultrasonic job, as first hand
knowledge regarding testing.
Before introducing this Ultrasonic Testing Training, lots of accidents took place due to fatigue failure in
Axle. This fatigue was mainly started from wheel seat position of the axle. Due to press fitting of wheel on axle
stress develop in vulnerable position i.e. inner wheel seat and outer wheel seat. During running of the train,
fatigue crack develop from these points and increases during completion of each cycle. As a result ultimate
failure of the Axle occurs causing an accident which incurs a loss of life in Passenger Train and lakhs of rupees
goods damages in Goods Train. The number of accidents occur due to axle failure have been minimised after
introducing the ultrasonic testing of axles & wheels. Now a days the accident due to axle failure is negligible.
Similarly the introduction of Ultrasonic Testing of Rails & Rail welds reduces the accident due to Rail failure.
The ultrasonic testing of Rail was introduced in early 60s. At present it is one of the best preventive maintenance
of rail. Initially only rails were tested ultrasonically. But the testing scope has been extended to Alumino
Thermic, Flash Butt, Gas Pressure welded joints, Switch Expansion Joints and Points & Crossings.
The persons who are doing Ultrasonic job are trained in the NDT Training Centre at RDSO/Lucknow.
This is the only Training Centre of Indian Railways for Ultrasonic Testing.
Some times Zonal Railways are pressing hard for giving Training to their Railways. Actually the RDSO
Training Centre is well equipped for providing training to Supervisors and Officers. There is a modern class
room with desklet type chair. It helps student for writing down their notes comfortably. There is a Workshop for
practical training where simulated rails were kept. The trainees have to find out the crack during practical
classes. There is hostel arrangement for boarding the trainees so the total environment of the RDSO Training
Centre is a learning attitude. If the training is incorporated in the Zonal Railways, the ideal class room, well
equipped Workshop with simulated rail etc. will not be available. So the training will be incomplete. More over,
as the Supervisors will be available in their Railway, they may be called by their Senior Officers if any urgency
arises. Some trainees may attend classes from their houses. So the day to day problems of the family have to
face them. All these factors will create a hindrance in proper attention to the study. As this training is purely on
safety related job, so attention in the studies both theoretical and Practical are very essential. Only successful
candidates are allowed to undertake ultrasonic test.
After taking training the Supervisors are testing the Axles and Rails in the Zonal Railways and Production
Units. They reject the crack axle found flaw in the shop floor and withdraw the crack rail detected by Ultrasonic
Flaw detection Machine. As a result accident avoided after getting its ultimate failure in the service. So this
Training Centre has a great roll to minimize axle and rail failure in service.
88
TRAINING OF PERSONNEL IN ULTRASONIC TESTING OF RAILS AND AXLES
89
ULTRASONICS IN RAILWAYS
3. Ultrasonic Waves, Mechanical Waves through an Elastic Body, Parameter of a Wave, Designation and
Units of Wave Parameter, Decibel, Wave Length, and dimension of a given flaw.
4. Ultrasonic Wave - Longitudinal Transverse and Surface Waves.
5. Properties of Sound Waves - Reflection, Refraction, Diffraction, Absorption & Scattering.
6. Transmission of Ultrasonic Beam from One Medium to another medium at Normal Incidence to the
Boundary and at an Angle to the Boundary.
7. Conversion of Ultrasonic Wave-Trajectories No. 1, 2 & 3.
8. Piezoelectric effect, Transducers, Properties of Different Piezoelectric crystals.
9. Probes used in Ultrasonic Testing, Normal Probes, Angle Probes, Calibration and checking methods of
probes.
10. Principle, Application and Testing Technique of Pulse-Echo reflection method.
11. Block Diagram of a Flaw Detector: Principle and Working of different parts.
12. Important characteristics of ultrasonic flaw detectors viz. Linearity of Time Base, Linearity of Amplification,
Resolution, Dead Zone etc. and their measurement.
13. Scanning Techniques - far end, low angle & high angle.
14. Method of Ultrasonic Testing and Acceptance standard for wrought wheels.
15. Ultrasonic testing of new axles.
16. Axle metallurgy and axle defects.
The topics covered under practical of Ultrasonic testing of axles and wheels are as under :
1. Familiarization with different control knobs of USFD.
2. Horizontal scale calibration of USFD for different ranges.
3. Horizontal scale calibration of USFD for shear waves.
4. Characteristics checking of USFD and probes.
5. Far-end scanning of axles.
6. UST of axle using Trace Delay technique.
7. Near-End Low Angle scanning.
8. High Angle scanning.
9. UST of wheel disc.
The General topics covered under 4 week regular course for 1Atrasonic testing of rails and rail welds are
as under:-
1. Various NDT methods, their principle and application.
2. Acoustics, Subsonic, Sonics and Ultrasonic Waves: their Industrial Application: Ultrasonic for Non-
Destructive Testing and Ultrasonic Spectrum.
3. Ultrasonic Waves, Mechanical Waves through an Elastic Body, Parameter of a wave, designation and units
of wave parameter, decibel, wave length, and dimension of a given flaw.
90
TRAINING OF PERSONNEL IN ULTRASONIC TESTING OF RAILS AND AXLES
91
ULTRASONICS IN RAILWAYS
The topics covered under practical of Ultrasonic testing of rail & rail welds are as under:
a) Familiarization with different control knobs of USFD.
b) Horizontal scale calibration of USFD for different ranges.
c) Horizontal scale calibration of USFD for shear waves.
d) Characteristics checking of USFD and probes.
e) Sensitivity of USFD for UST of rails.
f) Ultrasonic testing of rails on track.
g) UST of AT welded rail joints.
h) UST of FB & GP welded rail joints.
The topics covered under Refresher Course for Ultrasonic testing of Axles & Wheels are as under:-
a) Axles Metallurgy, axle specification and effects.
b) Re-capitulation of basic fundamental of ultrasonic waves.
c) Assessment of USFD and accessories.
d) Panel discussion on problem related to UST of axle and equipment.
e) Latest development in UST of axle and wheels.
f) Practical demonstration of new techniques.
The topics covered under Refresher Course for Ultrasonic testing of Rails & Rail Welds are as under :-
a) Rail Metallurgy, rail specification and defects in rails.
b) Re-capitulation of basic fundamentals of ultrasonic waves.
c) Assessment of USFD and accessories.
d) Panel discussion on problems related to UST of rails and equipment.
e) Latest development in UST of rails and welds.
f) Practical demonstration of end techniques.
The persons who are qualified in written and practical examination are eligible for getting certificate for
doing ultrasonic job for three years. After that they have to come for one week Refresher Course. An examination
is also conducted after completion of the course. The topics covered are Non destructive testing of materials,
Ultrasonic testing methods and their application, new technique in ultrasonic testing like Phased Array, EMAT
etc.
Two days Appreciation Course is also organised for managerial cadre of Indian Railways to keep them
aware with the knowledge of ultrasonic testing technique and also to guide and sort out difficulties faced by
Operators in the field. The teaching is provided through audiovisual system. Classroom is well equipped with
modern sitting arrangement, adequate lighting and air-conditioned environment.
92
army printing press
www.armyprintingpress.com
Lucknow (0522) 2481164
Appendices
ULTRASONICS IN RAILWAYS
94
APPENDICES
List of Appendix
Appendix I : Approved sources for ultrasonic equipment for rail & axle testing.
Appendix III : List of IRS Specification relating to Ultrasonic Testing prepared by RDSO.
95
ULTRASONICS IN RAILWAYS
96
APPENDICES
Appendix I
97
ULTRASONICS IN RAILWAYS
98
APPENDICES
Appendix II
CRANE AXLE
99
ULTRASONICS IN RAILWAYS
100
APPENDICES
101
ULTRASONICS IN RAILWAYS
S
N
1
CARRIAGE (BG) / EMU 2
102
APPENDICES
103
ULTRASONICS IN RAILWAYS
4
S
N
4
1
4
2
4
3
4
4
5
4
6
4
7
4
8
9
1
1
1
1
1
1
1
104
APPENDICES
CARRIAGE (NG)
S.
S. Class/type
Class /type Drg. No. Drg. No. Issued on Issued M&C Report
on M&C
No.
No. No Report No
11 Matheron Light
Suspension Railway LA-66/M (C.Rly.)
bearing 15.2.80 1976 K-194K-294
--
22 C&Wpin (WP)
Crank W/WL-3133 12.11.80 Aug.77K-215K-172
--
33 C&W Link BEML
Swing W/WL-3139 C/BE-465912.11.80 May 78K-214K-177
44 Leading
Crank pinaxle(Driving
YP/YG CCC/Rail car 15.2.84 11.1.79K-296K-191
--
5 unit) Rail
SGCI car of C & W
bearing MISCELLANEOUS -- ITEMS 9.5.79 K-285
6.5 Trailor Axle
Coupling rod Rail
YP/YGcar CCC/Rail car/32 18.3.87 25.9.80Not printed
-- Not printed
7.6. Diesel Rail car NRD1
Draft gear bolt (EMU) SKDP-2602 24.7.87
NA/306/M/ALT- 9.12.85 K-367K-332
(Driving) 5/C.Rly.
8.7. Frontcore
Solid Axleinsulator
of Motor SKDP-237 26.8.87 3.4.87 Not printed
-- K-354
9. coach of NRD1
WDM2 loco crank shaft 10141790 15.9.93 Not printed
8.
10. Trailor coach axle of LA.81/M (C.Rly.)
Guide valve lever yoke for WDM1,WDM2,WDS5 & ER.10210714 25.1.88 16.5.94K-359Not printed
Diesel Rail car (NG)
WDS6
9. Driving axle (Driving CCC/Rail car/31-A 26.2.88 K-360
unit) of Diesel Rail car
(NG)
10. C & W Ex.B.L.Rly.(NG) SCR/KWV LA 3051/M 25.10.88 K-376
11. C & W (NG) KPA 40/67 C & W 19.4.89 K-383
12. Diesel Rail Car (NG) NDR/WL-203-203/X 3.7.90/30.6.90 K-395
powered axle
13. Diesel Rail Car (NG) NDR/WL-201 & 201/X 15.11.90 Not printed
Trailing Axle
14. Diesel Rail Car (Revised) CCC/Rail car/32/E.Rly. 29.9.93 Not printed
105
ULTRASONICS IN RAILWAYS
11. Standardisation of ultrasonic testing of thermit welded TPP technique March 95 Not printed
combination joints (60/52 Kg)
12. WDS4 loco side rod /coupling rod (WDS4A,WDS4B 1 WDS4/3 64 20.10.95 Not printed
& WDS4D)
13. Bolster suspension pin for Trailor coach & motor MG/T-0-5-023 & May 95 Not printed
coach EMU/M-0-5-007
14. Standardisation of ultrasonic testing of TSC stud of CI.FN-812 22.5.96 Not printed
WDM2 loco in fitted condition.
15. Standardisation of ultrasonic testing of Manganese -- 1994 Not printed
pins of electric loco.
16. Radiator Fan blade of Diesel loco. -- 16.6.99 MC-27
17. Code of procedure for ultrasonic testing of Butt weld -- -- MC-4
joints of bogie frames for Railway rolling stock.
18. Equaliser spring seat guide pin fitted in electric SK.DL-3867 Dec.2001 MC-48
locomotive.
19. UST of container flat wheel. -- 14.1.2002 MC-49
20. Procedure for ultrasonic testing of AT welded Rail -- July 2002 MC-52
joints of 75 mm gap.
21. Equaliser beams, Compansating beam and Links Feb 05 MC 87
22. UST of Rail using Sperry RSU Walking stick May 05 MC 88
23. Ust of air box channel and base rail ( lamination test ) June 06 MC- 107
of GM Loco
24 Ust of air box assembly butt welded joints of GM June 06 MC- 108
Loco S
N
WAGON (BG &MG) 1
2
6
7
9
1
106
APPENDICES
ARMATURE SHAFT
S. DESCRIPTION OF ITEM DRG.NO. DT./YR. M&C
N. OF ISSUE REPORT
NO.
1 Armature shaft TAO-659 -- July 77 K-164
2 Armature shaft of EMU coach AE1/133AZ EMU/B3/102 11.5.78 K-280
3 Armature shaft TAO-659 for WAM4 -- 17.5.79 K-203
4 Armature shaft TJAA/62(EMU) TJAA/62 29.11.79 K-276
5 Pinion End shaft MG-1580(WAG4) TMS/CNB/15&TRS 22.12.80 K-302
1009/0
6 Armature shaft of T.M.710A for WAM1(Part) -- March.82 --
7 Armature shaft of TMTJAA/40 (EMU) TJAA/40 May.82 K-246
8 Armature shaft of TM253/BX/4601/AZ (EMU) ER/KPA/EL-TM 22.9.82 K-282
2HE053A
9 Armature shaft of Hitachi-HS1038Br(EMU) -- 13.10.82 K-260
10 Armature shaft TDK-5442 (MG-EMU) TDK-5442-A 5.11.82 K-261
11 Armature shaft 710A with slno.14 ER/KPA/EL/TM- -- K-249
IMI.081
12 Armature shaft TDK-5620A(BG-EMU) RES-400689 7.1.83 K-275
13 Armature shaft TM165/4939AZ WAM4/WDM2 ELW/BSL/WAM4/2110 28.1.83 K-264
-189&BHEL/F/4625385
14 Pinion End Shaft MG1580(hollow)-WAG4 WAG/476/CNB/TM 11.2.83 K-277
15 Armature shaft of TM HS-1091Ar for WAG2 HS-1091Ar 25.4.84 K-298
16 Armature shaft of WDM2 (GE make) CR/CI/EL-237 7.5.84 K-299
17 Armature shaft TMMU-252(EMU) EMU/CI/586 11.7.84 K-303
18 Armature shaft of TAO-659 for WAP1 1.TWD.092.456 22.10.84 K-310
(modified)
19 Armature shaft of TM 133AY(EMU) W.Rly.POH-69/49/R 31.12.84 K-315
20 Armature shaft of TM510(A&B) EMU TEAA/1 23.3.85 K-318
21 Armature shaft of TM HS3738B2 of WCM4 TH4LA-163/R2 9.1.86 K-335
22 Armature shaft of TM type MB-3045A for ER/KPA/ELREW276.5 10.2.86 K-334
WAM2=WDM2 69
107
ULTRASONICS IN RAILWAYS
S
N
1
2
3
4
5
6
9
1
1
1
1
108
APPENDICES
110
APPENDICES
Appendix III
LIST OF SPECIFICATION RELATING TO
ULTRASONIC TESTING PREPARED BY RDSO
S. Name of the Specification Old specification No. New Specification No. Issued
No. (Month/
Year)
1. Technical specification for hand M&C/NDT/19/93 M&C/NDT/102/2000 March-
operated double rail tester (Pulse 2000
echo type) for testing of rails in
track for flaws.
2. Specification for material used in M&C/NDT/4/91 M&C/NDT/105/2001 May 2001
penetrant examination
3. Specification for test panels (Ni-Cr) M&C/NDT/5/91 M&C/NDT/106 Proposed
4. Specification for ultraviolet lamp M&C/NDT/6/91 M&C/NDT/107 Proposed
(hand held)
5. Specification for ultrasonic M&C/NDT/7/91 M&C/NDT/108 Proposed
intensity meter.
6. Specification for magnetic particle M&C/NDT/8/91 M&C/NDT/109 Proposed
used in Magnetic particle
examination.
7. Specification for keto's Ring. M&C/NDT/9/91 M&C/NDT/110 Proposed
8. Specification for AC/half wave DC M&C/NDT/15/91 M&C/NDT/111/2001 July - 2001
electromagnet yoke type.
9. Technical specification for lathe M&C/NDT/18/92 M&CNDT/114/2000 Proposed
centre probe for ultrasonic testing (M&C/NDT/5/5 dt
of BG axle using contact method. 23.2.98)
10. Technical specification of Data -- M&C/NDT/115/2000 May 2004
logger for recording of the test Rev,-1 May 2004
details obtained from ultrasonic rail
tester during rail examination.
11. Technical specification for piezo M&C/NDT/16/91 M&C/NDT/116/2000 March -
electric probes for ultrasonic testing 2000
of railway components using
contact method.
12. Specification for carrying case of -- M&C/NDT/119/2001 April -
UFD for AT weld joint inspection. 2001
13. Technical specification of U.T. -- M&C/NDT/120/2001 May - 2005
equipment for AT welded rail (Rev.-2)
joints.
111
ULTRASONICS IN RAILWAYS
112
APPENDICES
Appendix IV
S. Document Description
No.
1. IS: 1182 - 1983 Recommended practice for radiographic examination of fusion welded butt
joints in steel plate
2. IS: 2417 - 2003 Glossary of terms used in ultrasonic non-destructive testing
3. IS : 2478 - 1981 Glossary of terms relating to industrial radiology
4. IS: 2595 - 1978 Code of practice for radiographic testing
5. IS: 2598 - 1966 Safety code for industrial radiology
6. IS: 2953 - 1985 Glossary of terms used for inspection of welds and cating radiographs
7. IS: 3657 - 1978 Radiographic image quality indicators
8. IS: 3658 - 1981 Code of practice for liquid penetrant flaw detection
9. IS: 3664 - 1981 Code of practice for ultrasonic pulse echo testing by contact and immersion
method
10. IS: 3703 - 1966 Code of practice for magnetic particle flaw detection
11. IS: 4225 - 2004 Recommended practice for straight beam ultrasonic testing of steel plates
12. IS: 4260 - 1986 Recommended practice for ultrasonic testing of butt welded in ferritic steel
13. IS : 4853 - 1982 Recommended practice for radiograph inspection of fusion welded butt joints
in steel pipes
14. IS: 4904 - 1990 Calibration blocks for used in Ultrasonic Non destructive testing
15. IS: 6394 - 1986 Code of practice for ultrasonic testing of seamless metallic tubular products
by contact and immersion method
16. IS: 7343 - 1986 Code of practice for ultrasonic testing of ferrous welded pipes and tubular
products
17. IS: 7666 - 1988 Ultrasonic examination of ferrite castings of carbon and low alloy steel -
recommended procedure
18. IS : 7743 - 1975 Recommended practice for magnetic particle testing and inspection of steel
forgings. 113
19. IS: 8791 - 1978 Code of practice for ultrasonic detection of ferritic steel forgings
20. IS: 11626 - 1986 Recommended practice for ultrasonic testing aand acceptance for forging
quality steel blooms
ULTRASONICS IN RAILWAYS
Appendix (V)
A. British Specification
1.1 BS :
EN 12668-3 : 2000 Non destructive testing - characterization and verification of ultrasonic examination 2B
equipment-part-3 : combined equipment. 3
D
3
1.2 Aerospace Series D
3
4
4
4
D
B. American Standard
D
2.1 ASTM
A.418-74 Ultrasonic testing and inspection of turbine and generator steel rotor forgings.
A.435-75 Specification for straight beam ultrasonic examination of steel plates for pressure vessels.
A.531-74 Recommended Practice for ultrasonic inspection of turbine generators steel retaining rings.
A:577 Ultrasonic angle-beam examination of steel plates.
A:578-75 Specification for straight beam ultrasonic examination of plain and clad steel plates for
special applications.
A:609 Longitudinal Beam Ultrasonic inspection of Carbon and Low Alloy Steel Castings.
A: 745 Ultrasonic Examination of Austenitic Steel Forgings.
B : 509-77 Specification for supplementary requirements for nickel alloy plate for Nuclear application.
114
APPENDICES
B : 510-77 Specification for supplementary requirements for nickel alloy rod and bar for Nuclear
application.
B : 513-77 Specification for supplementary requirements for nickel alloy seamless pipe and tube for
nuclear application.
B : 594-74 Ultrasonic inspection of aluminium alloy wrought product for aerospace specification.
B : 597 Test Method for Pulse Velocity Through Concrete.
B : 2845 Test Method for Pulse Velocities and ultrasonic Elastic constants of Rock.
D : 2966 Test Method for Cavitations Erosion-Corrosion Characteristics of Aluminium in Engine
Coolants Using Ultrasonic Energy.
E : 113-74 Ultrasonic testing by resonance method.
E : 114-75 Ultrasonic pulse echo straight beam testing by the contact method.
E : 127-75 Fabricating and checking of aluminium alloy, ultrasonic reference blocks.
E : 164-74 Ultrasonic contact examination of weldment.
E : 165-02 Standard test method for liquid penetrant examination.
E : 213-77 Ultrasonic inspection of metal pipe and tubing for longitudinal discontinuities.
E : 214-74 Immersed ultrasonic testing by the reflection method, using pulsed longitudinal waves.
E : 273-68 Ultrasonic inspection of longitudinal and spiral welds of welded pipes and tubing.
E : 317-68 Evaluating performance characteristics of pulse echo ultrasonic testing systems.
E : 428-75 Fabrication and control of steel reference blocks used in ultrasonic inspection.
E : 453 Recommended Practice for Examination of Fuel Element Cladding including the
Determination of the Mechanical properties.
E : 494-75 Measuring Ultrasonic velocity in materials.
E : 500-74 Definitions of terms relating to ultrasonic testing.
E : 587-76 Ultrasonic angle beam examination by the contact method.
E : 588-76 Detection of large inclusions in bearing quality steel by the ultrasonic method.
E : 664 Measurement of the Apparent Attention of Longitudinal Ultrasonic waves by Immersion
Method.
E : 709-95 Standard guide for magnetic particle examination.
E : 797 Measuring Thickness by Manual Ultrasonic Pulse echo Contact Method.
E : 804 Calibration of an Ultrasonic Evaluation of Socket and Butt joints of Thermoplastic piping.
E : 1444-94 Standard Practice for Magnetic Particle Examination.
F : 600 Non-destructive Ultrasonic Evaluation of Socket and Butt joints of Thermoplastic piping.
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ULTRASONICS IN RAILWAYS
ASME Sec.I
PW : 11 Radiographic and ultrasonic examination of boilers fabricated by welding.
PW : 52 Acceptance standard for ultrasonic examination of boilers fabricated by welding.
ASME Sec.III
NB : 2532 Ultrasonic examination procedure for plates.
NB : 2542 Ultrasonic examination of forgings & bars.
NB : 2552 Ultrasonic examination of seamless and welded tubular products and fittings.
NB : 2560 Examination and repair of tubular products and fittings welded with filler metal.
NB : 2572 Ultrasonic examination of statically and centrifugally cast products (ferritic steel
casting.
NB : 2584 Ultrasonic examination of bolts, studs and nuts of sizes greater than 2.
NB : 2585 Ultrasonic examination of bolts, studs and nuts of sizes greater than 4
NB : 5330 Ultrasonic acceptance standard for welds.
UF : 55 Ultrasonic examination of pressure vessels fabricated by forgings.
UW : 11 Radiographic and ultrasonic examination of pressure vessels fabricated by welding.
UW : 53 Technique for ultrasonic examination of welded joints in pneumatically tested
pressure vessels.
ASME Sec.V Boiler and pressure vessel code : Non-destructive Examination.
ASME Sec.VIII
Appendix VII Mandatory appendix : examination of steel castings.
Appendix U Non-Mandatory appendix : Ultrasonic examination of welds.
AF : 703 Ultrasonic examination of forged fabrications.
AM : 203 Ultrasonic examination of all product forms of ferrous materials.
AM : 252-2 Ultrasonic examination of steel castings.
AM : 402 Ultrasonic examination of all product forms of non-ferrous materials.
ASME Sec. IX
I.W.A. 22232 In-service ultrasonic examination of nuclear power plant components.
116
APPENDICES
Appendix.III
Mandatory appendix : In service ultrasonic examination of class 1 & 2,
ferritic steel piping systems for nuclear power plants.
C. French Specifications
D. German Specifications
DIN : 54119 Non-destructive testing ultrasonic definitions.
DIN : 54120 Non-destructive testing, reference blocks and its use for the adjustment and
control of ultrasonic echo equipment.
DIN : 54122 Non-destructive testing, reference block 2 and its use for the adjustment and
control of pulse echo equipment.
NF : A04.305.74 Ultrasonic testing of steel plates, methods of testing definition of qualities.
NF : A04.3111.64 Ultrasonic testing, calibration blocks, ferrous products and steel pieces.
E. International Standard Organisation
NF : A49.200.72 Seamless steel tubes for higher temperature and pressure application, testing
ISO : 2400-72 by ultrasonic,Reference
classification according
blocks to quality
2 for the and various
calibration application.
of equipment of ultrasonic testing of
NF : A49.870 welds in steel.
Seamless steel tubes for high temperature and pressure application testing by
ultrasonic for detection of longitudinal defects.
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ULTRASONICS IN RAILWAYS
Appendix VI
GLOSSARY OF ULTRASONICS & NDT METHODS
l A-Scan Display - A data presentation method in which signal amplitude is plotted along the y-axis versus
time on the x-axis. The horizontal distance between any two signals represents the material distance
between the two conditions causing the signals. In a linear system, the vertical excursion is proportional to
the amplitude of the signal.
l Absorption - The taking up of energy from the medium through which it passes.
l Absorption Coefficient - The ratio of energy absorbed by a medium or material to the energy incident on
the surface. If a flux through a material decreases with distance x in proportion to e-ax, then a is called the
absorption coefficient. Also known as the absorption factor; absorption ratio; coefficient of absorption.
l Absorption Coefficient, Linear - The fractional decrease in transmitted intensity per unit of absorber
thickness. It is usually designated by the symbol .
l Accelerator - A device that accelerates charged atomic particles to high energies. An x-ray machine or a
betatron is an accelerator.
l Acceptance Standard - A controlled specimen containing natural or artificial discontinuities that are well
defined and similar to the maximum acceptable discontinuity, in size and extent, in the product.
l Acoustic Emission Testing (AE) - A nondestructive testing method that listens for transient elastic-
waves generated due to a rapid release of strain energy caused by a structural alteration in a solid material.
l Acoustic Impedance (Z)- The resistance of a material to the passage of sound waves. The value of this
material property is the product of the material density and sound velocity. The acoustic impedance of a
material determines how much sound will be transmitted and reflected when the wave encounters a boundary
with another material. The larger the difference in acoustic impedance between two materials, the larger
the amount of reflected energy will be.
l Acoustic Plane Wave - A disturbance of molecular matter (sound energy) for which the wave disturbance
is distributed uniformly over a planar surface (same phase / same amplitude)
l Acoustic Properties - Intrinsic characteristics of any particular material that describe how sound travels
through it. Such characteristics include the density, acoustic impedance, and sound velocity.
l ACPD - Acronym for Alternating Current Potential Drop.
l Amplifier - A device to increase or amplify electric impulses.
l Amplitude - (1) The maximum absolute value obtained by the disturbance of a wave or any quantity that
varies periodically. (2) The vertical height of a received signal on an A-scan. It is measured from peak to
peak for an RF presentation or from base to peak for a video presentation.
l Angle Beam Testing - An ultrasound testing technique that uses an incidence wave angle other than 90
degrees to the test surface. The refracted angle of the sound energy is calculated using Snells law.
l Angle Beam Transducers - A device used generated sound energy, send the energy into a material at
angle other than 90 degrees to the surface, and receive reflected energy and convert it to electrical pulses.
118
APPENDICES
l Angle of Incidence - The angle between the direction of propagation of an electromagnetic or acoustic
wave (or ray) incident on a body and the local normal to that body.
l Angle of Reflection - The angle between the direction of propagation of an electromagnetic or acoustic
wave (or ray) reflected by a body and the local normal to that body.
l Angle of Refraction - The angle between the direction of propagation of an electromagnetic or acoustic
wave (or ray) refracted by an optically homogeneous body and the local normal to that body.
l Angstrom - A unit of length equal to 0.0000000001 or (1 x 10-10) meter.
l Angular Frequency - For any oscillation, the number of vibrations per unit time, multiplied by 2. Also
known as angular velocity and radian frequency.
l Anisotropy - The characteristic of a substance for which a physical property, such as the elastic properties,
varies with the direction along which the measurement is made.
l Annealing - Any treatment of metal at an elevated temperature for the purpose of softening, removing
residual stresses, recrystallization and other purposes.
l Area-Amplitude Blocks - Calibration blocks in which there are a series of flat-bottomed holes of varying
diameter.
l Array Transducer - A transducer made up of several individually piezoelectric elements connected so
that the signals they transmit or receive may be treated separately or combined as desired.
l Artificial Discontinuity - A feature, such as a notch, hole or crack, that is manufactured to closely resemble
a natural defect.
l Attenuation - The reduction in the level of a quantity, such as the intensity of a wave or radiation.
l Attenuation Coefficient - A factor which is determined by the degree of reduction in sound wave energy
per unit distance traveled. It is composed of two parts, one (absorption) proportional to frequency, the
other (scattering) dependent on the ratio of grain size or particle size to wavelength.
l Attenuator - A device for causing or measuring attenuation. Usually calibrated in decibels.
l B-scan - A data presentation method applied to pulse echo techniques. It produces a two-dimensional
view of a cross-sectional plane through the test object. The horizontal sweep is proportional to the distance
along the test object and the vertical sweep is proportional to depth, showing the front and back surfaces
and discontinuities between.
l Baseline - The reference line in a measurement by triangulation. (I.e. The horizontal trace across the A-
scan display. It represents time and is generally related to material distance or thickness.)
l Beachmarks - Macroscopic lines on a fatigue fracture that show the location of the tip of the fatigue crack
at some point in time. Must not be confused with striations, which are extremely small and are formed in
a different way.
l Beam Profiles - A measurement of the intensity of the beam across its width (or profile). It provides
valuable information about transducer sound field characteristics. Transverse beam profiles are created by
scanning the transducer across a target (usually either a steel ball or rod) at a given distance from the
transducer face and are used to determine focal spot size and beam symmetry. Axial beam profiles are
created by recording the pulse-echo amplitude of the sound field as a function of distance from the transducer
face and provide data on depth of field and focal length.
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ULTRASONICS IN RAILWAYS
l Brittle Rupture - A material failure mechanism that results with little or no plastic (permanent) deformation
prior to fracture.
l C-scan - a data presentation method applied to pulse echo and transmission techniques. It yields a two-
dimensional plan view of the object. No indication of depth is given unless special gating procedures are
used.
l Calibration - The process whereby the magnitude of the output of a measuring instrument is related to the
magnitude of the input force driving the instrument (i.e. Adjusting a weight scale to zero when there is
nothing on it).
l Cathode Ray Tube - A vacuum tube containing a screen on which ultrasonic scans or oscilloscope traces
may be displayed.
l Cleavage Fracture - A splitting fracture of a metal (usually polycrystalline) across the grains (or crystals).
l Color-Contrast Penetrant - A penetrant incorporating a color dye or sufficient intensity to give good
color contrast in indications against the background of the surface being tested, when viewed under white
light.
l Columnar Structure - A coarse structure of parallel columns of grains, having the long axis perpendicular
to the surface.
l Comparative Test Block - A metal block specially cracked and having two separate, but adjacent areas
for the application of different penetrants so that a direct comparison can be obtain.
l Compressional Wave - A wave in which the particle motion in the material is parallel to the wave
propagation direction. Also called a longitudinal wave.
l Contact Transducers - An ultrasonic transducer that is designed to be used in direct contact with the
surface of the test article.
l Control Echo - An ultrasonic reference signal from a constant reflector, such as the back reflection from
a smooth, regular surface. Loss of the control echo indicates that the UT system is not functioning properly
due to a problem such as coupling loss.
l Corner Effect - The strong reflection obtained when an ultrasonic beam is directed toward the intersection
of two or three mutually perpendicular surfaces.
l Corrosion - Deterioration of a metal by chemical or electrochemical reaction with its environment.
l Corrosion Fatigue - Cracking that initiates and propagates due to the application of repeated or fluctuating
stresses, and the initiation and propagation occurs more rapidly due to the presence of a corrosive
environment.
l Couplant - A substance (usually liquid) used between the transducer and the test surface to permit or
improve transmission of ultrasonic energy into the test object.
l Crack - A long narrow discontinuity
l Crack Growth Rate - The change in crack length per number of fatigue cycles.
l Critical Angle - The first angel of the incident sound wave that generates a refracted wave that travels
along the incident surface. The first angle that results in a surface following longitudinal wave is known as
the 1st critical angle and the first angle that results in surface following shear wave is known as the 2nd
critical angle.
120
APPENDICES
l Crystal - A three-dimensional array or atoms having a certain regularity in its arrangement. A crystal is
composed of many cells or lattices, in which the atoms are arranged. In the field of metallurgy, a crystal is
often called a grain.
l Cutoff Frequency - The upper or lower frequency beyond which no appreciable energy is transmitted.
l Cycle (Hertz) - One complete set of recurrent values of a periodic quantity comprises a cycle.
l Damping Material - A highly absorbent material used to cause rapid decay of vibration. The material
bonded to the back of the piezoelectric element of a transducer to limit the duration of vibrations.
l Dead Zone - In ultrasonic testing, the interval following the initial pulse where the transducer ring down
prevents detection or interpretation of reflected energy (echoes). In contact ultrasonic testing, the area just
below the the surface of a test object that can not be inspected because of the transducer is still ringing
down and not yet ready to receive signals.
l Decibel - A logarithmic unit for expressing power relationships. n = 10 log10(I1/I2) where n is the difference
of decibels of intensities 1 & 2.
l Defect - A discontinuity or other imperfection causing a reduction in the quality of a material or component.
l Delay Line - A material (liquid or solid) placed in front of a transducer to cause a time delay between the
initial pulse and the front surface reflection.
l Density - The mass of a substance per unit volume.
l Discontinuity - a break in the continuity of a medium or material.
l Distance Amplitude Correction (DAC) - Compensation of gain as a function of time for difference in
amplitude of reflections from equal reflectors at different sound travel distances. Refers also to compensation
by electronic means such as swept gain, time corrected gain, time variable gain and sensitivity time control.
l Distance-Amplitude Blocks - A set of ultrasonic reference specimens in which each specimen has a
different metal path length to a equal-sized reflector. The specimens are used to develop distance amplitude
response curves.
l Divergence - An improper term used to describe the spreading of ultrasonic waves beyond the near field.
It is a function of transducer diameter and wavelength in the medium.
l Ductile - Permitting plastic (or permanently) prior to eventual fracture.
l Echo - A signal indicating reflected acoustic energy.
l Echoes - A sound wave that continues to bounce around a room or off other barriers, or reverberate, until
it has lost all its energy.
l Eddy Currents - Circular induced currents that are generated by an alternating current in the nearby coil.
l Eddy Current Inspection - An electromagnetic technique used on conductive materials for crack detection
or the rapid sorting of small components for either flaws, size variations, or material variation, as well as
other applications.
l Electromagnetic Acoustic Transducer - A device using the magneto effect to generate and receive acoustic
signals for ultrasonic nondestructive tests.
l Electromagnetic Acoustic Transducers (EMATS) - A scanning device which transmits and receives
ultrasonic waves.
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ULTRASONICS IN RAILWAYS
l False Indication - A test indication that could be interpreted as originating from a discontinuity but which
actually originates where no discontinuity exists.
l Far Field - The zone beyond the near field in front of the transducer in which signal amplitude decreases
monotonically in proportion to distance from the
l Fatigue - The phenomenon leading to fracture under repeated or fluctuating stresses having a maximum
values less than the tensile strength of the material. Fatigue fractures are progressive, beginning as minute
cracks that grow under the action of the fluctuating stresses.
l Ferrite - Essentially pure iron in the microstructure of an iron or steel specimen. It may have a small
amount of carbon (less than 0.02 wt%). Also called alpha iron.
l Ferromagnetic Materials - Materials that can be magnetized.
l Filet - a radius (curvature) imparted to inside meeting surfaces; a blended curve joining an internal corner
to two lateral surfaces.
l Flat Bottom Hole - A type of reflector commonly used in reference standards. The end (bottom) surface
of the hole is the reflector.
l Flaw - A defect.
l Flaw Location Scale - A specially graduated ruler that can be attached to an angle beam transducer to
relate the position of an indication on the cathode ray tube screen to the actual location of a discontinuity
within the test object.
l Focused Beam - A sound beam that converges to a cross section smaller than that generated by the
transducer.
l Focused Transducer - A transducer that produces a focused sound beam.
l Focusing - Concentration or convergence of energy into a small beam.
l Fracture - A break, or separation, of a part into two or more pieces.
l Frequency - The number of waves that pass a given point in a specified unit of time.
l Frequency, Pulse Repetition - The number of pulses per second.
l Frequency, Test - The nominal ultrasonic wave frequency used in a test.
l Gain Control - A control which varies the amplification of the ultrasonic system. Also considered the
sensitivity control.
l Gas Porosity - A cavity caused by entrapped gas. Essentially a smooth-sided bubble within the metal,
where the metal solidified before the gas could escape to the atmosphere. Also called gas pocket.
l Gate - An electronic device for monitoring signals in a selected segment of the trace on an A-scan display.
- The interval along the baseline that is monitored.
l Grain - The more common term for crystal, a three-dimensional array of atoms having a certain regularity
in its internal arrangement. The grain is composed of many cells, or lattices, in which the atoms are
arranged on the metal involved.
l Grain Size - Size of the crystals in metal when compared with a standard. Usually referred to as being
fine, medium, or coarse.
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APPENDICES
l Heat Treatment - Heating and cooling a metal or alloy in such a way as to obtain desired conditions or
properties.
l Heat-Affected Zone - That portion of the base metal which was not melted during brazing, cutting or
welding, but whose microstructure and physical properties were altered by the heat.
l Hertz - One cycle per second.
l Horizontal Linearity - A measure of the proportionality between the positions of the indications appearing
on the horizontal trace and the positions of their sources.
l Hot Cracks - Appear as ragged dark lines of variable width and numerous branches internally or at the
surface.
l Hot Tear - A fracture formed in a metal during solidification because of hindered contraction.
l Imaging - A process to produce an image of an opaque object on film for study.
l Immersion Method - The test method in which the test object and the transducer are submerged in a
liquid (usually water) that acts as the coupling medium. The transducer is not usually in contact with the
test object.
l Impurities - Elements or compounds whose presence in a material is undesired.
l Inclusion - Nonmetallic particles, usually compounds in a metal matrix. Usually considered undesirable,
though in some cases, such as in free machining metals, inclusions may be deliberately introduced to
improve mach inability.
l Incomplete Fusion - Welding fusion which is less than compete. Failure of weld metal to fuse completely
with the base metal or preceding bead.
l Incomplete Joint Penetration (Lack of Fusion) - Welding fusion that fails to penetrate to complete
thickness of the materials being joined. Appears as elongated darkened lines of varying length and width
which may occur in any part of the welding groove.
l Incomplete Penetration - Welding root penetration which is less than complete or failure of a root pass
and backing pass to fuse with each other.
l Inherent Defects - Discontinuities which are normal in the material at the time it originally solidifies
from the molten state.
l Initial Pulse - The pulse applied to excite the transducer. It is the first indication on the screen if the sweep
is undelayed. Also called the main bang. May refer to an electrical pulse or an acoustic pulse.
l Intensity - The amount of energy a sound has over an area. The same sound is more intense if you hear it
in a smaller area. In general, sounds with a higher intensity are louder.
l Interpretation - The determination of the source and relevancy of an ultrasonic indication.
l Lamb Wave -A type of ultrasonic wave propagation in which the wave is guided between two parallel
surfaces of the test object. The mode and velocity depend on the product of the test frequency and the
separation between the surfaces.
l Linearity -The characteristic of an instrument that is revealed by a linear change in reflected signal
amplitude. The vertical linearity is determined by plotting the change in ratios of signal amplitude from
two reflecting areas. The horizontal linearity is determined by plotting the distance the signal is displaced
along the sweep against the change in material thickness.
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ULTRASONICS IN RAILWAYS
124
APPENDICES
l Plane Wave - wave in which points of same phase lie on parallel plane surfaces.
l Polycrystalline - Pertaining to a solid metal composed of many crystals, such as an ordinary commercial
metal.
l Probe Index - The point on a shear wave or surface wave transducer through which the emergent beam
axis passes.
l Pulse - A transient electrical or ultrasonic signal.
l Pulse Echo Method - An ultrasonic test method in which discontinuities are detected by return echoes
from the transmitted pulses.
l Radiograph - a photographic recording produced by the passage of radiation through a subject onto a
film.
l Range Control - A means of expanding the pattern obtained on the cathode ray tube so that any portion of
the total distance being tested can be presented.
l Ray - A beam of energy of small cross section.
l Rayleigh Waves - An ultrasonic wave that propagates along the surface of a test object. The particle
motion is elliptical in a plane perpendicular to the surface, decreasing rapidly with depth below the surface.
The effective depth of penetration is considered to be about one wavelength.
l Receiver - The section of the ultrasonic instrument that amplifies echoes returning from the test object.
Also, the transducer that picks up the echoes.
l Reference Blocks - A block or series of blocks of material containing artificial or natural discontinuities
or one or more reflecting areas at one or more distances from the test surface, which are used for reference
in defining the size and distance of defective areas in materials.
l Refracted Beam - A beam that occurs in the second medium when an ultrasonic beam is incident at an
acute angel on the interface between two media having different sound velocities.
l Rejection Level - The level above or below which a signal is an indication of a rejectable discontinuity.
l Residual Method (Magnetic Particle) - Bath is applied after current has been shut off; that is, the indicating
particles are on the part when residual (remaining) magnetic field is present.
l Residual Stress Internal stress; stress present in a body that is free from external forces or thermal
gradients.
l Resolution - The ability to clearly distinguish signals obtained from two reflective surfaces with a minimum
difference in depth. Near surface resolution is the ability to clearly distinguish a signal from a reflector at
a minimum distance under the near surface without interference from the initial pulse signal. Far surface
resolution is the ability to clearly distinguish signals from the back surface when the sound beam is normal
to that back surface.
l Resolving power - A measure of the ability of an ultrasonic system to separate two signals close together
in time or distance.
l Scanning - Movement of the transducer over the surface of the test object in a controlled manner so as to
achieve complete coverage. May be either contract or immersion method.
l Scattering Ultrasonic - Dispersion of ultrasonic waves in a medium due to causes other than absorption.
l Search Unit - An assembly comprising a piezoelectric element, backing material (damping), wear plate or
125
ULTRASONICS IN RAILWAYS
wedge (optional) and leads enclosed in a housing. Also called transducer or probe.
l Segregation - Nonuniform distribution of alloying elements, impurities or microphases.
l Sensitivity - A measure of the ability to detect small signals. Limited by the signal-to-noise ratio.
l Shadow - A region in a test object that cannot be reached by ultrasonic energy traveling in a given direction.
Shadows are caused by geometry or the presence of intervening large discontinuities.
l Shallow Discontinuity - A discontinuity open to the surface of a solid object which possesses little depth
in proportion to the width of this opening. A scratch or nick may be a shallow discontinuity in this sense.
l Shear - A type of force that causes or tends to cause two regions of the same part or assembly to slide
relative to each other in a direction parallel to their plane of contact. May be considered on a microscale
when planes of atoms slide across each other during permanent, or plastic, deformation. May also be
considered on a macroscale when gross movement occurs along one or more planes, as when a metal is cut
or sheared by another metal.
l Shear Fracture - Fracture that occurs when shear stresses exceed shear fractures are transverse fracture
of a ductile metal under a torsional (twisting) stress, and fracture of a rivet cut by sliding movement of the
joined parts in opposite directions, like the action of a the pair of scissors.
l Shear Waves - Waves which move perpendicular to the direction the wave propagates.
l Shear Wave Transducer - An angle beam transducer designed to cause converted shear waves to propagate
at a nominal angle in a specified test medium.
l Skip Distance - In angle beam tests of plate or pipe, the distance from the sound entry point to the first
reflection point on the same surface. See V-path.
l Soft X-Rays - The quality or penetrating power of x-radiation; their penetrating power is relatively slight.
l Sound - Mechanical vibrations transmitted by an elastic medium.
l Spectrum - The amplitude distribution of frequencies in a signal.
l Test Frequency - The frequency f vibration of the ultrasonic transducer employed for ultrasonic testing.
l Transducer - An electroacoustic or magnetoacoustic device containing an element for converting electrical
energy into acoustical energy and vice versa. See search unit.
l Transducer Element - The component in a transducer that actually converts the electrical energy into
acoustical energy and vice versa. The transducer element is often made of a piezoelectric material or a
magnetostrictive material.
l Transmission Angle - The incident angle of a transmitted ultrasonic beam. It is zero degrees when the
beam is perpendicular (normal) to the test surface.
l Transmitter - The transducer that emits ultrasonic energy. - The electrical circuits that generate the signals
emitted by the transducer.
l Transverse - Literally across, usually signifying a direction or plane perpendicular to the axis of a part.
l Two-crystal Method - Use of 2 crystals for sending and receiving. May be pulse-echo or through
transmission method.
l UT - Abbreviation for the ultrasonic method of nondestructive testing.
l Ultrasonic - A term referring to acoustic vibration frequencies greater than about 20,000 hertz.
126
APPENDICES
l Ultrasonic Spectrum - Usually, the frequency range from 20,000 to 107 hertz. But may extend much
higher in special applications.
l Ultrasonic Testing - The transmission of high-frequency sound waves into a material to detect imperfections
or to locate changes in material properties.
l Ultrasonic Waves - Sound waves too high in frequency for humans to hear.
l Water Washable Penetrant - A penetrant containing emulsifying such that it does not require the allocation
of a separate emulsifying agent to facilitate removal by eater rinsing.
l Wavefront - In a wave disturbance, the locus of points having the same phase.
l Wavelength - The distance needed in the propagation direction for a wave to go through a complete cycle.
l Wedge - A device used to direct ultrasonic energy into a test object at an acute angle.
l Wheel Transducer - A device that couples ultrasonic energy to a test object through the rolling contact
area of a wheel containing a liquid and one or more transducers.
l X-rays - A form of electromagnetic radiation with wavelengths shorter than those of ultraviolet light.
127
ULTRASONICS IN RAILWAYS
Appendix (VII)
References
1. Ultrasonic Testing of Railway Components by S.WISE, Asstt. Director (Mech. Testing), Engineering
Research Division, British Railways Board, Derby.
5. Practical Ultrasonic Indian Society for Non Destructive Testing C.V. Subramanian.
128
APPENDICES
The standard of our Training Centre is also recommended by Bureau of Indian Standards (BIS). They
stated that The Training is imparted in accordance to IS: 13805-2001 Certification Scheme for Level-II in
Ultrasonic Testing. The certificate issued after the training given to the Supervisors level/officers of Indian
Railways on Ultrasonic Testing covering all the criteria and content laid down in BIS Specification IS: 13805-
2001. It is indicated that the course model confirms to all the criteria of Level-II in NDT/UT of IS: 13805:2004.
BIS has given us permission to write level-II in the certificate issued to trainees.
The National Certificated Board for Non-destructive Testing has also issued certificate of Indian Society
for Nondestructive Testing (ISNT) and American Society for Non-destructive Testing (ASNT) Level-II &
Level-III.
129