Nondestructive testing (NDT) is a group of analysis techniques that evaluate materials without causing damage, saving time and money in product evaluation. Common methods include eddy-current, magnetic-particle, dye penetrant, radiographic, ultrasonic, and visual testing, each with unique procedures and applications across various engineering fields. The techniques are crucial for detecting flaws, ensuring component integrity, and preventing costly failures.

1. Non Destructive
Testing (NDT)
By
Mr. H.P.Varade
Assistant Professor
Sanjivani College of Engineering,
Kopargaon, District-Ahmednagar

2. What is NDT?
• Nondestructive testing or non-destructive
testing (NDT) is a wide group of analysis
techniques used in science and technology
industry to evaluate the properties of a
material, component or system without
causing damage.
• The terms nondestructive examination
(NDE), nondestructive inspection (NDI), and
nondestructive evaluation (NDE) are also
commonly used to describe this technology.

3. • Because NDT does not permanently alter the
article being inspected, it is a highly valuable
technique that can save both money and time
in product evaluation, troubleshooting, and
research. The six most frequently used NDT
methods are eddy-current, magnetic-particle,
dye/liquid penetrant, radiographic, ultrasonic,
and visual testing

4.  NDT does not directly measure mechanical
properties but they are used to locate defects or
flaws in the component.
 Flaws reduce useful life of component resulting
in premature failure even with a sound design
and proper selection of materials.
 To obtain high level of reliability , defect should
be absent or at minimum level.
 NDT is carried out periodically.
 Replacement of component before its
premature failure to avoid dangerous results.

5. Applications of NDT
• NDT is commonly used in forensic
engineering, mechanical engineering,
petroleum engineering, electrical engineering,
civil engineering, systems engineering,
aeronautical engineering, medicine, and art.
• Innovations in the field of nondestructive
testing have had a profound impact on
medical imaging, including on
echocardiography, medical ultrasonography,
and digital radiography.

6. DIFFERENT NDT METHODS
1. DYE PENETRATION TEST
2. SONIC TEST
3. ULTRASONIC TEST
4. MAGNETIC PARTICLE TEST
5. RADIOGRAPHY TEST
6. EDDY CURRENT TEST

7. 1.Dye Penetrant Inspection
 Invisible cracks, porosity and other defects on
the surface of components easily detected by
this technique.
 Components may be ferrous, nonferrous, plastic,
glass or ceramic.
 Procedure:-
1. Cleaning of surface.(Grease, oil, any other
material).
2. Drying of surface.

8. 3. Applying dye-penetrant on clean and dry surface.
It is allowed to penetrate in surface flaws.
i) Liquid Soluble Penetrant
ii) Fluroscent
4. Removing excess penetrant by soft or clean
cotton.
5. Applying developer on surface. This pulls out dye
from flaws and flaws are revealed by colour of
dye. Instead of developer, fine developing
powder or talc powder can be sprinkled on the
surface.

11. Advantages of Dye Penetrant
Inspection
• This test can be applied to almost any type of
metals, nonmetals, magnetic or non magnetic
type.
• Simple to utilize and control.
• Results of test can be interpreted fastly.
• Cost of test is very less as it does not require
any instrument or electronic display units.
• Sensitivity is greater than that of magnetic
particle testing.

12. Disadvantages of Dye Penetrant
Inspection
• Cleaning of components is must before and
after testing to avoid rusting
• Misleading results may be obtained in case of
components with surface films and coatings
• Only surface defects can be detected
• Test is not applicable for powder metallurgical
components

13. 2.Sonic Inspection
 Sound is created in the component and from
quality of sound ,presence of defect is judged.
 e.g. C.I. piece gives a dull sound as compared
to steel piece if dropped from certain height
on the floor.
 e.g. Cups, saucer, earthen pots ,coconuts.

14. Principle-
1. Measure of time required by ultrasonic vibrations
to penetrate material of interest , reflect from
opposite side or from internal discontinuity and
return to point from where first introduced.
2. Behaviour of waves through cycle with regard to
time is recorded on CRO screen.
3. By observing this presence of defect and their
location can be detected.
Two types of Ultrasonic testing method-
i)Pulse –echo method
ii) Transmission Method
3.Ultrasonic Test/inspection

15. i)Pulse –Echo method:-

17. ii) Transmission Method:-

18. Advantages of Ultrasonic Test
• Better detection of flaws situated deep in
metal due to superior penetrating power of
ultrasonic waves
• High sensitivity, better accuracy and reliability
• The equipment is portable and easy to handle
• Output of test can be processed by computer
which lead to improved result reliability

19. Disadvantages of Ultrasonic Test
• Due to manual operation, careful attention
and highly skilled operators are required
• Irregular shaped and rough parts are very
difficult to examine
• Subsurface discontinuities are more difficult to
detect
• Couplants are needed for testing

20. 4.Magnetic Particle (Magnaflux)
Inspection
• It is used to detect various kinds of flaws in
ferromagnetic components such as weldings,
castings, forgings of iron and steel.
• Component to be inspected for flaws is
magnetized.
• In dry method of inspection special fine
ferromagnetic powder is applied on surface .

21. • This test is a very fast method of inspection
and often used to test aerospace components
and automobile parts.
• This test is generally used to detect internal
cracks like shrinkage cavities, hot tears, zones
of corrosion and non-metallic inclusions

22. Magnaflux Test Procedure:-
1. Cleaning Surface
2. Magnetization
3. Application of ferromagnetic Powder
4. Observation and Inspection
5. Demagnetization

23. Magnetic Particle /Magnaflux Inspection

26. Advantages of Magnaflux Test
• Sub-surface cracks can be easily detected
• Almost any shaped and sized component can
be tested for defects
• Instruments are portable and easy to handle
• Highly sensitive method to detect small and
shallow surface cracks

27. Disadvantages of Magnaflux Test
• Method is applicable only to ferromagnetic
materials
• Surface plating or thin paint coating affect the
sensitivity of the test
• After testing, demagnetization is a must
• Local heating and sparking is possible during
test hence proper care must be taken

28. 5. Radiography Test
• NDT method that utilizes x-rays or gamma
radiation to detect discontinuities in materials,
and to present their images on recording
medium.
• This includes X-rays, gamma rays and radio-
isotopes. This method is used to check internal
cracks, defects in materials which are made by
casting, welding, forging.
• Nowadays, radiography techniques are finding
more extensive applications in the field of
physical metallurgy and in the treatment of
various diseases.

29. • Rays are absorbed by the materials through
which they are passed in the proportion of
their density. The rays, after passing through
the components, show a picture on a
fluorescent screen or on a photographic plate.
• The cracks, blow holes and cavities appear
lighter, whereas inclusions of impurities
appear darker than the metal component.
• Developed photographic film show lighter and
darker areas to represent the radiograph of
defects in the component.

33. Advantages of Radiography Test
• X-ray radiography is highly sensitive, fast
method of finding defects
• X-ray radiography is suitable for various
applications due to its adjustable energy levels
• Gamma ray radiography has high penetrating
power hence can be used for more denser and
thicker materials
• A number of samples can be inspected at a
time by gamma ray radiography

34. Disadvantages of Radiography Test
• X-ray radiography can be applied for thinner
components due to its less penetrating power
• X-ray radiography allows only one component to
be tested at a time
• X-ray radiography involves high initial cost
• X-ray and gamma ray radiography involve
radiations which are hazardous to living beings
• Trained operators are required

35. 6.Eddy Current Testing
 Basic Principle:- When coil carrying alternating
current is brought near metallic specimen, eddy
currents are developed in specimen due to
electromagnetic induction.
Magnitude of induced EMI depend on –
i)Magnitude and frequency of alternating current
flowing in coil.
ii) Electrical conductivity of specimen.
iii) Magnetic permeability of specimen.

36. iv)Shape of specimen.
v)Relative positions of coil and specimen.
vi)Microstructure and hardness of Specimen.
vii)Amount and type of defects in the specimen.

40. Advantages ECT
• Test is quick and less time consuming
• Test can be automated easily
• Permanent record of test results can be easily
available
• Test is versatile and can be used for various
applications

41. Disadvantages of ECT
• The instrument standardization and
calibration is necessary from time to time
• Instruments and display units are costly
• Test can be applied to components of limited
size and shape

42. REFERENCES
• Material Science and Metallurgy for Engineers
by V D Kodgire and S V Kodgire
• www.wikipedia.com