Unit 6: Non-Destructive Testing
Syllabus
Non-Destructive Testing
- Classification of Non-destructive testing methods
- Principles of physics in Non-destructive Testing
- Advantages of Non-destructive testing methods
- Acoustic Emission Testing
- Ultrasonic (thickness measurement, flaw detection)
- Radiography testing
Nanotechnology
- Introduction to nanotechnology
- Quantum confinement and surface to volume ratio
- Properties of nanoparticles: optical, electrical, mechanical
- Applications of nanoparticles: Medical (targeted drug delivery), electronics, space and
defense, automobile
6.1.1 Introduction and classification of Nondestructive Testing
Destructive Testing: In this method, the sample under test is destroyed and cannot be used for any
purpose after the test. Examples are tensile test, impact test, etc. These tests are performed on
sample material out of the batch. These tests are used to find our mechanical properties like
hardness, compressive strength, yield strength and tensile strength, etc.
Objectives of Nondestructive testing (NDT):
- These tests do not change the structural properties of the material under the investigation.
- It is the process of inspecting, testing, or evaluating materials, components or assemblies for
discontinuities, or differences in characteristics without destroying the serviceability of the
part or system.
- Safety norms can be applied after the requirements of the test.
6.1.2 Classification of NDT methods and Physics Applied
- Classification of NDT Methods Nondestructive testing (NDT) is based on interrelation
between a physical field or a substance and a tested object.
- Few types of NDT are discussed as below:
Sr. NDT Method Physics employed Applications
1 Acoustic Application of mechanical load or rapid Flaws or irregularities inside the
temperature or pressure change to the part materials
being tested and analyzing its propagation.
2 Ultrasonic Echo sounding using ultrasonic Detection of flaws or irregularities
inside the materials.
Measurement of thickness of metal
sheets
3 Radiography Exposing the materials under test to x-rays Detection of Cracks, Cavities, Flaws,
Testing X- or -rays and taking impression Porosity of materials
rays or -rays
4 Magnetic Magnetic field is applied to the materials Continuity (flaw detection)
NDT methods and changes in the magnetic characteristics Dimensions, structural and
of the ferromagnetic materials are mechanical properties
detected
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, 5 Electric or Exposing the tested objects to electric (i) Measuring parameters of the
non-electric disturbance (e.g. electrostatic field, composition and structure of a
NDT methods constant AC or DC field) or non-electric material
disturbance (e.g. infrared, mechanical, etc.) (ii) Finding geometrical dimensions
of a tested object
(iii) Finding moisture level
6 Eddy-Current The interaction between an external Testing item dimensions,
NDT methods electromagnetic field and the measuring the diameter of wire,
electromagnetic field induced in the test rods and pipes, thickness of metal
object. plates and that of pipe walls
- In addition to these, other types of NDT methods are vibration analysis, leak testing
and integrated ones.
- In all the NDT methods, due to probable presence of defects in the tested object, the nature
of external applied field changes.
Distinction between destructive and non-destructive testing
Sr. Destructive testing Non-destructive testing
1 Tests are carried out to find properties and Tests are carried out to find properties and
behavior of the material under different the defects inside the material.
external conditions.
2 Properties of the material such as bending, Properties of the materials cannot be found
tensile strength, compression, strength can out.
be found out.
3 Defects inside the material such as flaw, Defects inside the material can be located.
cracks, porosity cannot be located.
4 Tests are not possible to carry out on entire Tests can be carried out on selected samples
batch of products as it will destroy all parts in randomly and results can be correlated to
production. other parts.
5 The object under testing is destroyed. The object under testing remains intact.
6 As tests involve destruction of part, the As tests do not involve destruction of part,
production cost increases as part needs to be the part under test remains intact and
replaced after tests. production cost can be reduced.
7 Examples: bending test, tensile test, Examples: Acoustic emission, ultrasonic
compression test, impact test, etc. testing, eddy current testing, radiography
testing etc.
6.1.3 Acoustic Emission Technique (AET)
Principle: A mechanical load or rapid temperature or pressure is applied to the material under test
and resulting stress waves generated are sensed by sensors.
Method:
• A localized external force such as an
abrupt mechanical load or rapid
temperature or pressure is applied to
the part of the material being tested.
• A small material displacement or
plastic deformation is produced inside
the material.
• This results into generation of stress waves inside the material in the form of short-lived,
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Syllabus
Non-Destructive Testing
- Classification of Non-destructive testing methods
- Principles of physics in Non-destructive Testing
- Advantages of Non-destructive testing methods
- Acoustic Emission Testing
- Ultrasonic (thickness measurement, flaw detection)
- Radiography testing
Nanotechnology
- Introduction to nanotechnology
- Quantum confinement and surface to volume ratio
- Properties of nanoparticles: optical, electrical, mechanical
- Applications of nanoparticles: Medical (targeted drug delivery), electronics, space and
defense, automobile
6.1.1 Introduction and classification of Nondestructive Testing
Destructive Testing: In this method, the sample under test is destroyed and cannot be used for any
purpose after the test. Examples are tensile test, impact test, etc. These tests are performed on
sample material out of the batch. These tests are used to find our mechanical properties like
hardness, compressive strength, yield strength and tensile strength, etc.
Objectives of Nondestructive testing (NDT):
- These tests do not change the structural properties of the material under the investigation.
- It is the process of inspecting, testing, or evaluating materials, components or assemblies for
discontinuities, or differences in characteristics without destroying the serviceability of the
part or system.
- Safety norms can be applied after the requirements of the test.
6.1.2 Classification of NDT methods and Physics Applied
- Classification of NDT Methods Nondestructive testing (NDT) is based on interrelation
between a physical field or a substance and a tested object.
- Few types of NDT are discussed as below:
Sr. NDT Method Physics employed Applications
1 Acoustic Application of mechanical load or rapid Flaws or irregularities inside the
temperature or pressure change to the part materials
being tested and analyzing its propagation.
2 Ultrasonic Echo sounding using ultrasonic Detection of flaws or irregularities
inside the materials.
Measurement of thickness of metal
sheets
3 Radiography Exposing the materials under test to x-rays Detection of Cracks, Cavities, Flaws,
Testing X- or -rays and taking impression Porosity of materials
rays or -rays
4 Magnetic Magnetic field is applied to the materials Continuity (flaw detection)
NDT methods and changes in the magnetic characteristics Dimensions, structural and
of the ferromagnetic materials are mechanical properties
detected
Page 1 of 12
, 5 Electric or Exposing the tested objects to electric (i) Measuring parameters of the
non-electric disturbance (e.g. electrostatic field, composition and structure of a
NDT methods constant AC or DC field) or non-electric material
disturbance (e.g. infrared, mechanical, etc.) (ii) Finding geometrical dimensions
of a tested object
(iii) Finding moisture level
6 Eddy-Current The interaction between an external Testing item dimensions,
NDT methods electromagnetic field and the measuring the diameter of wire,
electromagnetic field induced in the test rods and pipes, thickness of metal
object. plates and that of pipe walls
- In addition to these, other types of NDT methods are vibration analysis, leak testing
and integrated ones.
- In all the NDT methods, due to probable presence of defects in the tested object, the nature
of external applied field changes.
Distinction between destructive and non-destructive testing
Sr. Destructive testing Non-destructive testing
1 Tests are carried out to find properties and Tests are carried out to find properties and
behavior of the material under different the defects inside the material.
external conditions.
2 Properties of the material such as bending, Properties of the materials cannot be found
tensile strength, compression, strength can out.
be found out.
3 Defects inside the material such as flaw, Defects inside the material can be located.
cracks, porosity cannot be located.
4 Tests are not possible to carry out on entire Tests can be carried out on selected samples
batch of products as it will destroy all parts in randomly and results can be correlated to
production. other parts.
5 The object under testing is destroyed. The object under testing remains intact.
6 As tests involve destruction of part, the As tests do not involve destruction of part,
production cost increases as part needs to be the part under test remains intact and
replaced after tests. production cost can be reduced.
7 Examples: bending test, tensile test, Examples: Acoustic emission, ultrasonic
compression test, impact test, etc. testing, eddy current testing, radiography
testing etc.
6.1.3 Acoustic Emission Technique (AET)
Principle: A mechanical load or rapid temperature or pressure is applied to the material under test
and resulting stress waves generated are sensed by sensors.
Method:
• A localized external force such as an
abrupt mechanical load or rapid
temperature or pressure is applied to
the part of the material being tested.
• A small material displacement or
plastic deformation is produced inside
the material.
• This results into generation of stress waves inside the material in the form of short-lived,
Page 2 of 12
