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Файл:A Brief Description оf NDT Techniques. Учебное пособие по английскому языку
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A transducer is an instrument that is capable of converting energy from
one state to another. Ultrasonic transducers can transform electrical energy into sound energy and vice versa.
For ultrasonic flaw detection, standard transducers employ an active
element that is made of either a polymer, composite, or piezoelectric ceramic. When an electrical pulse of high voltage is applied to this element,
it vibrates through a particular spectrum of frequencies and produces
sound waves. When an incoming sound wave vibrates this element, it
produces an electrical pulse.
Cross section of typical contact transducer
In flaw detection applications, five types of ultrasonic transducers are
usually employed. They include contact transducers, immersion transducers, delay line transducers, angle beam transducers, and dual element
transducers.
Advanced Ultrasonic Flaw Detectors
Panametrics-NDT Epoch series are ultrasonic flaw detectors that are
compact and portable instruments based on microprocessor. They are
ideal for shop and field applications and display an ultrasonic waveform
that is easily understood by a trained operator, who detects and classifies
the flaws in test pieces. The series comprises a waveform display, an ultrasonic pulser/receiver, a data logging module, and software and hardware for signal capture and analysis. In order to optimize the performance
of transducer, pulse amplitude, damping and shape can be controlled.
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Likewise, in order to signal-to-noise ratios, receiver gain and bandwidth
can be modified.
Illustration of Ultrasonic Flaw Detection
Procedure of Ultrasonic Flaw Detection
A trained operator can identify particular echo patterns related to the
echo response from representative flaws and good parts. This can be done
by utilizing correct reference standards and accepted test procedures
along with a good knowledge of sound wave propagation. Two calibration standards such as straight beam testing and angle beam testing are
used in ultrasonic flaw detection. The latter technique is commonly used
in weld inspection.
Ultrasonic flaw detection is a comparative method. Although some
analog-based flaw detectors are still being produced, most modern instruments employ digital signal processing to promote enhanced stability and
accuracy.
Task 8. Vocabulary Check. Match the terms with the translation. You do not need all the terms.
42
transducer, software, sound wave, portable, immersion, accuracy,
delay, enhance
Translation
Term
1.
[n.] точность, правильность; тщательность,
меткость
2.
[n.] задержка, препятствие, отсрочка, замедление, выдержка [v.] задерживать, препятствовать, отсрочивать, откладывать
3.
[v.] увеличивать, усиливать, усугублять, повышать, совершенствовать
4.
[adj.] переносный, съемный, разборный
5.
[n.] программное обеспечение, программные системы
6.
[phr.] звуковая волна
7.
[n.] преобразователь, датчик, приемник
Task 9. Connect the halves of the given sentences:
1
A transducer is an in-
strument that is capable
A
are compact and portable instruments based on microprocessor.
2
For ultrasonic flaw detection, standard transducers employ an active element that
B
it produces an electrical
pulse. 3 When an electrical
pulse of high voltage is applied to this element,
C
it vibrates through a particular spectrum of frequencies and
produces sound waves.
4
When an incoming
sound wave vibrates this
element,
D
pulse amplitude, damping
and shape can be controlled.
5
Panametrics-NDT
Epoch series are ultrasonic
flaw detectors that
E
is made of either a polymer,
composite, or piezoelectric ceramic.
6
In order to optimize the
performance of transducer,
F
of converting energy from
one state to another.
43
7
A trained operator can
identify particular echo
patterns related to
G
most modern instruments
employ digital signal processing
to promote enhanced stability
and accuracy.
8
Although some analogbased flaw detectors are
still being produced,
H
the echo response from representative flaws and good
parts.
Task 10. Match the synonyms:
capable, propagation, likewise, immersion, respond, although
Synonyms
Term
1
acknowledge, answer, reply
2
admitting, while, albeit
3
generation, proliferation, multiplication
4
efficient, skillful, adequate
5
similarly, also, additionally
6
absorption, engagement, concentration
Advantages of Ultrasonic Flaw Detection
Thickness and lengths up to 914.4 cm (30 ft) can be tested. (For nu-
clear power, the thickness of metal does not exceed 30 - 40 cm, for
example, in the reactor vessel)
Position, size and type of defect can be determined.
Instant test results.
Portable.
Extremely sensitive if required.
Capable of being fully automated.
Access to at least one side necessary
Disadvantages of Ultrasonic Flaw Detection
No permanent record available unless one of the more sophisticated test results and data collection systems is used.
The operator can decide whether the test piece is defective or not
whilst the test is in progress.
Indications require interpretation (except for digital wall thickness gauges).
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Considerable degree of skill necessary to obtain the fullest infor-
A. investigate
1. отразиться, вернуться
B. transmit
2. преобразовать
C. bounce back
3. проводить
D. convert
4. захватывать
E. capture
5. передавать
F. conduct
6. обследовать
A. high frequency
B. internal discontinuity
C. rear wall
D. bonding layer
E. contact fluid
A. The Examiner sees whether there are any discontinuities.
B. The object is cleaned of any material that may interfere with
the analysis.
C. A transducer converts an electronic signal into ultrasonic
sound waves.
D. The Examiner applies a contact fluid to enable the ultrasonic
filler to make proper contact with the material.
E. The ultrasound equipment captures the reflected waves and
converts this into a visual signal.
F. If there are discontinuities, the exact location is determined
using calculations.
mation from the test.
Very thin sections can prove difficult.
LISTENING
Task 11. Match the verb with their Russian equivalents
Task 12. Give the definitions to the following terms
Task 13. Watch the video ‘Ultrasonic Testing’ and put the
stages in the correct order
https://www.youtube.com/watch?v=DgeQTw7q_xQ
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Task 14. Watch the video again and fill in the gaps with a word
or a short phrase
1) It is possible to investigate whether there are discontinuities un-
der the surface using ___________.
2) The vibrations can, however, be measured with sensitive measur-
ing ______.
3) Using this storage vessel our weld is checked for ____________.
4) Sound waves are transmitted into the material with the transducer
and an echo is sent back from the _________ or discontinuity.
5) In case of a discontinuity, sound is echoed back faster. Thus, we
can see if the material wall is thinning for instance, by ______.
6) The Examiner first applies a _________ to enable the ultrasonic
filler to make proper contact with the material.
7) This _________ serves to conduct the sound waves into the ma-
terial.
8) A transducer ______ an electronic signal into ultrasonic sound
waves.
9) The ultrasound equipment captures the _________ and converts
this into a visual signal.
10) If there is an indication, the exact location can be determined
using ______.
GRAMMAR
Quantifiers
Task 15. Complete each sentence with a quantifier. In two of
the sentences two quantifiers are possible.
all, any, both, each, either, enough, little, neither, no, some
a) Carston pic had ______ success in extending its business to the USA,
and soon had to close all its branches.
b) A late surge in sales produced just ______ income for the company
to survive.
c) ______ application received after the deadline will be rejected.
d) ______ of the two candidates made an opening statement before the
debate took place.
e) Bywater Ltd will have ______ thirty subsidiaries worldwide after its
expansion programme is complete.
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f) Becoming self-employed or setting up a limited company: in theory,
1. eddy currents
A. переменный ток
2. electromagnetic induction
B. контактный детектор
3. alternating current
C. преграда, препятствие
4. collapse
D. отслоение; расслаивание
5. obstacle
E. электромагнитная катушка
6. probe
F. тепловая обработка
7. coil
G. вихревые токи
8. case depth
H. резко падать
9. heat treatment
I. электромагнитная индукция
10. delamination
J. толщина слоя
______ option is open to the freelancer.
g) Some printers support automatic printing on ______ sides of the pa-
per (known as 'duplex printing').
h) Professor Chalmers claims that a virtual reality helmet that mimics
______ five senses will be ready within five years.
LESSON VII
EDDY CURRENT TESTING
Task 1. Match the terms with their Russian equivalents:
Task 2. Read the text and answer the following questions:
a) How are eddy currents used in NDT?
b) Why is NDT so important to our society?
c) Why is eddy current inspection preferable to other methods of
NDT?
d) What are the chief obstacles to applying eddy current testing?
e) What eddy current equipment and probes can you name?
Nondestructive testing (NDT) literally means testing materials without destroying them. In other words, we can look for defects in a variety
of metallic materials using eddy currents and never harm the material that
we are testing. This is important because if we destroy the material we
47
are testing, it does not do much good to test it in the first place. NDT is
very important because often the defects that we are looking for are not
visible because paint or some other coating may cover them. There might
also be defects that are so small they cannot be seen with our eyes or any
other visual method of inspection. Therefore, inspection methods such as
eddy current inspection have been developed to detect the defects.
Basic Principles of Eddy Current Inspection
Eddy current inspection is one of several NDT methods that use the
principal of “electromagnetism” as the basis for conducting examinations. Several other methods such as Remote Field Testing (RFT), Flux
Leakage and Barkhausen Noise also use this principle.
Eddy currents are created through a process called electromagnetic induction. When alternating current is applied to the conductor, such as
copper wire, a magnetic field develops in and around the conductor. This
magnetic field expands as the alternating current rises to maximum and
collapses as the current is reduced to zero. If another electrical conductor
is brought into the close proximity to this changing magnetic field, current
will be induced in this second conductor. Eddy currents are induced elec-
trical currents that flow in a circular path. They get their name from “eddies” that are formed when a liquid or gas flows in a circular path around
obstacles when conditions are right.
In order to generate eddy currents for an inspection, a “probe” is used.
Inside the probe is a length of electrical conductor material which is
formed into a coil.
One of the major advantages of eddy current as an NDT tool is the
variety of inspections and measurements that can be performed. In the
proper circumstances, eddy currents can be used for:
48
Crack detection
Material thickness measurements
Coating thickness measurements
Conductivity measurements for:
o Material identification
o Heat damage detection
o Case depth determination
o Heat treatment monitoring
Some of the advantages of eddy current inspection include:
Sensitive to small cracks and other defects
Detects surface and near surface defects
Inspection gives immediate results
Equipment is very portable
Method can be used for much more than flaw detection
Minimum part preparation is required
Test probe does not need to contact the part
Inspects complex shapes and sizes of conductive materials
Some of the limitations of eddy current inspection include:
Only conductive materials can be inspected
Surface must be accessible to the probe
Skill and training required is more extensive than other tech-
niques
Surface finish and roughness may interfere
Reference standards needed for setup
Depth of penetration is limited
Flaws such as delaminations that lie parallel to the probe coil
winding and probe scan direction are undetectable
Present State of Eddy Cur-
rent Inspection
Inspectors use eddy current testing to inspect for damage. Eddy
current inspection is used in a variety of industries to find defects and
make measurements. One of the
primary uses of eddy current testing
49
is for defect detection when the nature of the defect is well understood. In
general, the technique is used to inspect a relatively small area and the
probe design and test parameters must be established with a good understanding of the flaw that is to be detected. Since eddy currents tend to
concentrate at the surface of a material, they can only be used to detect
surface and near surface defects.
In thin materials such as tubing and sheet stock, eddy currents can be
used to measure the thickness of the material. This makes eddy current a
useful tool for detecting corrosion damage and other damage that causes
a thinning of the material. The technique is used to make corrosion thinning measurements on aircraft skins and in the walls of tubing used in
assemblies such as heat exchangers. Eddy current testing is also used to
measure the thickness of paints and other coatings.
Eddy currents are also affected by the electrical conductivity and magnetic permeability of materials. Therefore, eddy current measurements
can be used to sort materials and to tell if a material has seen high temperatures or been heat treated, which changes the conductivity of some
materials.
Eddy current equipment and probes can be purchased in a wide variety
of configurations. Eddyscopes and a conductivity tester come packaged
in very small and battery operated units for easy portability. Computer
based systems are also available that provide easy data manipulation features for the laboratory. Signal processing software has also been developed for trend removal, background subtraction, and noise reduction. Impedance analyzers are also sometimes used to allow improved quantitative eddy-current measurements. Some laboratories have multidimensional scanning capabilities that are used to produce images of the scan
regions. A few portable scanning systems also exist for special applications, such as scanning regions of aircraft fuselages.
Task 3. Mark the sentences T (true) or F (false).
a) The technique is often used to check a limited area, and the probe
design and test settings must be determined with a thorough analysis of
the problem to be identified.
b) When the nature of the flaw is too difficult to recognize, eddy
current inspection is one of the most common applications.
c) Eddy currents cannot be applied to measure the thickness of frag-
ile sections such as tubing and sheet stock. As a result, eddy current is an
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