Non destructive testing introduction

1. Unit-1
OVERVIEW OF NDT
By
GODWIN PITHALIS N E

2. ME6019
NON DESTRUCTIVE TESTING AND MATERIALS
OBJECTIVES:
 To study and understand the various Non
Destructive Evaluation and Testing methods,
theory and their industrial applications.
UNIT I OVERVIEW OF NDT
 NDT Versus Mechanical testing, Overview of the
Non Destructive Testing Methods for the
detection of manufacturing defects as well as
material characterisation. Relative merits and
limitations, Various physical characteristics of
materials and their applications in NDT., Visual
inspection – Unaided and aided.

3. UNIT II SURFACE NDE METHODS
Liquid Penetrant Testing - Principles, types and properties of
liquid penetrants, developers, advantages and limitations of
various methods, Testing Procedure, Interpretation of results.
Magnetic Particle Testing- Theory of magnetism, inspection
materials Magnetisation methods, Interpretation and evaluation
of test indications, Principles and methods of demagnetization,
Residual magnetism.
UNIT III THERMOGRAPHY AND EDDY CURRENT TESTING (ET)
Thermography- Principles, Contact and non contact inspection
methods, Techniques for applying liquid crystals, Advantages
and limitation - infrared radiation and infrared detectors,
Instrumentations and methods, applications. Eddy Current
Testing-Generation of eddy currents, Properties of eddy
currents, Eddy current sensing elements, Probes,
Instrumentation, Types of arrangement, Applications,
advantages, Limitations, Interpretation/Evaluation

4. UNIT IV ULTRASONIC TESTING (UT) AND ACOUSTIC EMISSION (AE)
Ultrasonic Testing-Principle, Transducers, transmission and pulse-
echo method, straight beam and angle beam, instrumentation,
data representation, A/Scan, B-scan, C-scan. Phased Array
Ultrasound, Time of Flight Diffraction. Acoustic Emission
Technique –Principle, AE parameters, Applications
UNIT V RADIOGRAPHY (RT) 10
Principle, interaction of X-Ray with matter, imaging, film and film
less techniques, types and use of filters and screens, geometric
factors, Inverse square, law, characteristics of films - graininess,
density, speed, contrast, characteristic curves, Penetrameters,
Exposure charts, Radiographic equivalence. Fluoroscopy- Xero-
Radiography, Computed Radiography, Computed Tomography
OUTCOMES:
Upon completion of this course, the students can able to use the
various Non Destructive Testing and Testing methods understand
for defects and characterization of industrial components

5.  In this type of testing, the component or specimen to
be tested is destroyed and cannot be reused.
 After testing, the component or specimen either breaks
or remains no longer useful for future use.
 As the name suggests, destructive testing (DT)
includes methods where the component or specimen
is broken down in order to determine physical and
mechanical properties such as strength, toughness,
ductility and hardness.
 Destructive testing is more suitable and economical
for mass production, as the cost of destroying a
small number of pieces is negligible. It is not
economical to do destructive testing where only one
or very few items are to be produced.

6.  Tensile test
 Compression test
 Shear test
 Hardness test
 Impact test
 Bending test
 Fatigue test
 Creep test
 Torsion test
 Chemical analysis, etc

7.  NDT stands for Non-Destructive testing
 As its name implies, non-destructive testing
means testing of materials without destroying
them.
 A non-destructive test is an examination of
an object which will not produce any kind of
damage or destruction to the sample and
after testing the material can be reused.

8.  Non-Destructive testing 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. In other words, when the inspection is
completed, the part can be used.
 NDT is a procedure which covers the
inspection and/or testing of any material,
component or assembly by means which do
not affect its ultimate serviceability.

9.  Material sorting
 Material characterization
 Property monitoring
 Thickness measurement
 Defect detection/ location
 Defect characterization
 Major task of NDT is to detect and identify the
range of defects.
Main objectives
 (i) To detect internal or surface flaws
 (ii)To measure the dimensions of the specimen
 (iii) To determine material structure or chemistry
 (iv) To evaluate material’s physical or mechanical
properties.

10.  Flaw Detection and Evaluation
 Leak Detection
 Location Determination
 Dimensional Measurements
 Structure and Microstructure Characterization
 Estimation of Mechanical and Physical
Properties
 Stress (Strain) and Dynamic Response
Measurements
 Material Sorting
 Chemical Composition Determination

11.  NDT allows parts and material to be inspected and measured
without damaging them. Because it allows inspection without
interfering with a product's final use, NDT provides an excellent
balance between quality control and cost-effectiveness.
What is NDE:
Non destructive evaluation (NDE) is a term that is often used
interchangeably with NDT.
However, technically, NDE is used to describe measurements that
are more quantitative in nature.
For example, an NDE method would not only locate a defect, but
it would also be used to measure something about that defect
such as its size, shape, and orientation.
NDE may be used to determine material properties, such as
fracture toughness, formability, and other physical
characteristics.

12.  There are NDE application at almost any stage
in the production or life cycle of a component.
◦ To assist in product development
◦ To screen or sort incoming materials
◦ To monitor, improve or control manufacturing
processes
◦ To verify proper processing such as heat treating
◦ To verify proper assembly
◦ To inspect for in-service damage

13.  To ensure product integrity and reliability
 To control manufacturing processes
 To lower production costs
 To maintain a uniformity in quality level
NDT tests can be performed …
(i) During manufacturing
(ii) After manufacturing
(iii) Even on parts that are already in service

14.  Inspection of Raw Products
 Inspection Following Secondary Processing
 In-Services Damage Inspection
Inspection of Raw Products
 Forgings,
 Castings,
 Extrusions,etc.

15.  Machining
 Welding
 Grinding
 Heat treating
 Plating

16.  Cracking
 Corrosion
 Erosion/Wear
 Heat Damage

17.  Using NDT, an entire production lot can be
inspected, or selected samples can be inspected
 Also different tests can be applied to the same
item, either simultaneous or sequentially, and the
same test can be repeated on the same specimen
for additional verification.
 It may be added that the NDT equipment is often
portable. This permits the use of NDT methods for
on-site testing in most locations.
 NDT does not permanently alter the specimen being
inspected, it is a high valuable technique that can
save both time and money in product evaluation,
trouble shooting, and research.
 NDT make components more reliable, safe and
economical.

18.  The equipments are easy to handle
 Defects can be detected without damaging the
components
 Methods are quick and accurate
 Components can be sorted out on the basis of
electrical, magnetic or chemical properties
 Test results and other information can be
conveniently recorded on paper films, cassettes,
floppies, DVD, CD. etc

19. NON DESTRUCTIVE TEST DESTRUCTIVE TEST
Used for finding out defects of
materials
Used for finding out the properties
of the material
Load is not applied on the material Load is applied on the material
No load applications, so no chance
for material damage
Due to load application, material
gets damaged
No requirement of special
equipments
Special equipments are required
Non expensive Expensive
Less skill Skill is required
e.g: dye penetrate test, ultrasonic,
radiography, etc
e.g: tensile test, compression test,
hardness test, etc

20.  Visual inspection is the simplest, fastest and most
widely used non-destructive testing method.
 Visual inspection is carried out with naked
eye(unaided) or using some optical aids (aided)
such as mirrors, magnifying glasses and
microscopes etc.
Definition:
 Visual inspection is defined as the examination of
material or component for conditions of non-
conformance using light and the eyes alone or in
conjunction with various aids.
 Visual inspection often also involves seeing,
listening, feeling and sometimes even smelling
the component being inspected.

21.  Visual inspection is commonly employed to
support other NDT methods
 Other NDT methods require visual intervention
to interpret images obtained while carrying out
examinations. At some point, all NDT methods
fall back on visual testing.
 For Example, LPT uses dyes that rely on the
inspectors ability to visually identify surface
indications.
 Digital detectors and computer technology
have made it possible to automate visual
inspections. This is known as machine vision.

22. Visual testing is commonly used
 To detect surface characteristics such as
surface finish, scratches, cracks, colour, wear
and corrosion
 To check alignment of mating surfaces
 To check of the components
 To check the evidence of leaking
 To check internal side defects

23.  Simple and easy to use
 Relatively inexpensive
 Testing speed is high
 Testing can be performed on components which
are in-service
 Permanent records are available when latest
equipments are used
 Almost all materials can inspect
Limitations:
 Limited to detection of surface flaws
 The test results depend on skill and knowledge
of tester
 Eye resolution is week
 Eye fatigue

24. Classified on the basis of use of aids used
 (i) Unaided or direct visual testing
 (ii) Aided visual testing
Unaided or direct visual testing
 As the name suggests, the unaided visual
testing is carried out with naked eye (without
using any optical aids)
 The most important instrument in visual
inspection is human eye

25.  Human eye is the most fascinating and valuable tool
in NDT
 It has greater precision and accuracy than many of
the most sophisticated cameras. It has unique
focusing capabilities and has the ability to work in
conjunction with the human brain so that it can be
trained to find specific details or characteristics in a
test specimen.
 It has the ability to differentiate and distinguish
between colours and their tones/shades
characteristics as well
 Human eye is capable of assessing many visual
characteristics and identifying various types of
discontinuities
 The eye can perform accurate inspections to detect
size, shape, colour, depth, brightness, contrast and
texture

26.  As the name suggests, the aided inspection is
carried out with the help of optical aids (such as
magnifying glasses, microscopes, borescopes,
fiberscopes) and a variety of other optical
imaging and image enhancement tools.
 The optical aids are mainly used for
(i) Magnification of defects which cannot be
detected by unaided visual inspection
(ii) Assisting in the inspection of defects
(iii) areas where not easily accessible to human eye

27. The optical aids used for visual inspection are
(i) Magnifying Mirrors (small, angled mirrors)
(ii) Magnifying glasses, eye loupes, multi-lens
magnifiers, measuring magnifiers
(iii) Microscopes(optical and electron)
(iv) Boroscopes
(v) Fiberscopes and videoscopes
(vi) Telescopes
(vii) Periscopes
(viii) Optical comparators
(ix) Optical flats(for surface flatness measurements)
(x) Photographic records
(xi) Closed-circuit television (CCTV) systems
(xii) Machine vision systems
(xiii) Image enhancement (computer analysis and
enhancement)

28.  When inspecting areas not easily accessible, a magnifying
mirror can be used
 Depending on the test specimen, the mirror can be of any
size.
(ii) Magnifying Glass
 A magnifying glass can be used for closer inspection of
suspicious looking areas
 It generally consists of a simple lens for lower power
magnification and double or multiple lenses for higher
magnification
(iii) Microscopes:
 Microscope is a multiple element magnifier for providing
very high magnified image of small object
 The simple microscopes consists of a convex lens. The
object is placed between lens and focus length of lens, so
that an erect, virtual and magnified image is formed. The
size of the image of an object depends upon the angle
subtended at the eye by the object.(known as visual angle)

29.  Borescope are optical instrument designed
for remote viewing of objects. They are used
to inspect the inside of a narrow tube, bore or
chamber.
 Borescopes is a precision optical instrument
with built-in illumination
 Borescopes, also called endoscopes or
endoprobes consist of superior optical
systems and high intensity light sources.
 Some Borescopes provide magnification
option, zoom controls.
 Because of the variety of applications,
Borescopes are manufactured in rigid,
extended, flexible and micro designs.

30.  Modern fiberscope and videoscopes, due to their
small size and flexibility, can provide access to
internal areas inaccessible to rigid borescopes.
 Using these, digital images can be captured and
processed in real time. With the aid of laser
lights, the area and depth of many surface
defects can also be determined.
(vi) Telescopes
 Telescope is an instrument that collects radiation
from a distant object in order to produce an
image of it.
 An optical telescope uses visual radiations
 The telescopes are used for providing visual
examination of the inaccessible surfaces.

31.  Optical comparators are the magnifying
devices for visual examination and
measurement.
 A comparator produces 2D enlarged image of
an object on a large ground-glass screen.
 Optical comparators project the image of
small parts onto a large projection screen.
The magnified image is then compared
against an optical comparator chart, which is
a magnified outline drawing of the workpiece
being gauged.

32.  Periscope is an instrument used for remote
observation of inaccessible areas.
 In simple periscope, two right angle reflecting
prisms are utilized in combination with a
series of lenses.
 The periscopes are commonly used for
remote visual inspection in hazardous
situation such as radiations areas, toxic
environment and for overhead viewing of
areas involving obstacles.

33.  Inspection of cleanliness in machines
 Checking for corrosion, erosion and deformities of
machine components
 Checking for ruptures, cracks and wear of parts in
the equipment.
 Monitoring of manometers, pressure and
temperatures
 Monitoring of oil level, greasing and greasing
apparatus.
 Monitoring of the operational conditions of
systems or machines.
 Visual Testing of welds
 Visual Testing of Pumps
 Visual Testing of hydraulic systems
 Visual Testing of Belt Pulley
 Visual Testing of Forging Discontinuities

34. Most basic and common
inspection method.
Tools include
fiberscopes,
borescopes, magnifying
glasses and mirrors.
Robotic crawlers permit
observation in hazardous
or tight areas, such as air
ducts, reactors, pipelines.
Portable video inspection
unit with zoom allows
inspection of large tanks
and vessels, railroad
tank cars, sewer lines.