This document discusses non-destructive testing (NDT) methods, with a focus on visual inspection techniques. It defines NDT as examining materials and components without destroying them to find defects. Several NDT methods are described including visual inspection, liquid penetrant testing, magnetic particle testing, etc. Visual inspection can be unaided or aided using tools like magnifying mirrors, boroscopes, and robotic crawlers. Factors that influence visual testing like surface conditions, environment, and inspector fatigue are also covered. The document provides examples of visual inspection applications and lists advantages and limitations of various NDT methods.

1. M.KARTHIKEYAN
ASSISTANT PROFESSOR
DEPARTMENT OF MECHANICAL ENGINEERING
AAA COLLEGE OF ENGINEERING & TECHNOLOGY, SIVAKASI
karthikeyan@aaacet.ac.in
OML751 TESTING OF MATERIALS

2. UNIT III NON DESTRUCTIVE TESTING
1. Visual inspection
2. Liquid penetrant test
3. Magnetic particle test
4. Thermography test
5. Radiographic test
6. Eddy current test
7. Ultrasonic test
8. Acoustic emission
Principles, Techniques, Methods, Advantages and Limitations,
Applications.

3. DESTRUCTIVE
TESTING
NON-DESTRUCTIVE
TESTING

4. DESTRUCTIVE TEST NON DESTRUCTIVE TEST
1 Used for finding out the
properties of the material
Used for finding out defects of
materials
2 Load is applied on the material Load is not applied on the
material
3 Due to load application, material
gets damaged
No load applications, so no
chance for material damage
4 Tested material cannot be
reused.
Tested material can be reused.
5 Tests are mostly quantitative
measurements.
Tests are mostly qualitative
and rarely quantitative
measurements.
6 All measurements are direct Most of the measurements are

5. DESTRUCTIVE TEST NON DESTRUCTIVE TEST
7 In – service inspection is not
possible
In – service inspection is
possible
8 Specimen preparation is
necessary.
Little or no specimen
preparation is required.
9 Can measure only one
property at a time.
Can measure many
parameters.
10 Time conception for inspection
is more.
Rapid inspection is possible
11 Skilled man power is not
required to interpret the
results
Skilled man power is required
to interpret the results

6. INTRODUCTION TO NDT
Non-destructive testing is used for the examination of materials
and components without changing or destroying their usefulness.
NDT or NDE can be used to find, size and locate surface and
subsurface flaws and defects.
NDT is necessary to assure safety and reliability.
NDT is a Quality Assurance management tool.
Typical examples are found in aircraft, spacecraft (shuttle), motor
vehicles, pipelines, bridges, trains, power stations, refineries,
buildings and oil platforms which are all inspected using NDT.
It requires an understanding of the various methods available,
their capabilities and limitations, knowledge of the relevant
standards and specifications for performing the tests

7. IMPORTANCE OF NDT
1. NDT increases the safety and reliability of the product during
operation.
2. It decreases the cost of the product by reducing scrap and
conserving materials, labor and energy.
3. It enhances the reputation of the manufacturer as a producer
of quality goods.
4. All of the above factors boost the sales of the product which
bring more economical benefits for the manufacturer.
5. NDT is also used widely for routine or periodic determination
of quality of the plants and structures during service.

9. VISUAL INSPECTION
 Visual Inspection is one of the most widely used Non-
Destructive Testing methods for the detection of discontinuities
before they cause major problems,
EXAMPLES:
1. Poor welding
2. Surface defects
3. Corrosion pits
4. General condition
5. Degradation
6. Blockages and foreign materials.

10.  Visual Inspection means the inspection of equipment and
structures using a combination of human senses such as vision,
hearing, touch and smell.
 Visual Inspection is sometimes carried out in conjunction with
devices such as a low power magnifying glass, boroscopes,
fiberscopes, digital video borescopes, camera systems and
robotic crawler systems.
 Generally, almost any specimen can be visually examined to
determine the accuracy of its fabrication.
 For example, visual inspection can be used to determine
whether the part was fabricated to the correct size, whether the
part is complete, or whether all of the parts have been
appropriately incorporated into the device

11. TYPES OF VISUAL INSPECTION
1. Direct unaided visual testing
2. Direct aided visual testing
3. Remote visual testing
2.DIRECT AIDED VISUAL TESTING +
3. REMOTE VISUAL TESTING = AIDED VISUAL INSPECTION

12. 1. DIRECT UNAIDED VISUAL TESTING
 There is no interruption between the eye and the object.

13.  It is also Known as Direct Visual Inspection
 It can be accomplished with the help of naked eye
 It can done with out the help of optical aids
 Defects can be detected are – cracks, Corrosion layer,
surface porosity, Misalignment of mated parts

14. THE EYE
 Human eye is the most valuable NDT Tool
 Sensitivity of the human eye varies according to the light
source
 Human eye has an excellent visual perception
 Yellow green light of wavelength 5560°A is the most
suitable light for human eye at normal condition

15. LIMITATIONS OF UNAIDED VISUAL INSPECTIONS
 Can identify only large discontinuities
 Limited to surface discontinuities
 Skilled labour required
 Result depend on the eye resolution of the inspector
 It may cause eye fatigue to the inspector

16. 2.DIRECT AIDED VISUAL TESTING
 The nature of the image is not modified. Modification of the
image is only allowed by :
 magnification with for example a mirror, a lens, an endoscope ;
 spectral or density filtering by a filter lens.

17. 3. REMOTE VISUAL TESTING
 The nature of the image is modified : for example the optical
image is converted into an electronic image by a camera.

18. 2.DIRECT AIDED VISUAL TESTING +
3. REMOTE VISUAL TESTING = AIDED VISUAL
INSPECTION
 It is also known as Indirect Visual Inspection
 It is performed using optical instruments
 This will identify the defects which cannot detect with human
eye
 It permits visibility to areas are not accessible to human eye

19. AIDED VISUAL INSPECTION - TOOLS
1. MAGNIFYING MIRRORS
2. MAGNIFYING GLASS
3. MICROSCOPE
4. BORESCOPE
5. ENDOSCOPE
6. FIBROSCOPES
7. ROBOTIC CRAWLERS

20. MAGNIFYING MIRRORS
 It is also known as concave spherical mirrors
 It is used to magnify the areas which are not accessible
to human eye.

21. MAGNIFYING GLASS
 It is also called as Hand Lens
 This lens is used to produce a magnified Image
 Magnification depends upon the position where it is
being placed between the human eye and the object
 For higher power magnification, double or multiple lenses
are used

22. MICROSCOPE
 Microscope is used to magnify the image of a small
object

23. BORESCOPE
 It is used to inspect the inside of a narrow tube
 It is a flexible tube with an eyepiece at one end and objective
lens at another end
 Light is passed through the lens and to obtain a clear image
 Available range is 2.5 mm to 19 mm

24. ENDOSCOPE
 It is bit superior than borescope
 Magnification factor of 10X is obtained
 Available up to smaller dia of 1.7 mm and length upto
100-150mm

25. FIBROSCOPES
 Also called fibre optic borescope
 Dia range of about 3 to 12.5mm and length varies
between 60 – 365 cm

26. ROBOTIC CRAWLERS
• Robotic crawlers permit observation in hazardous or tight
areas, such as air ducts, reactors, pipelines.

27. FACTORS THAT AFFECT VISUAL TESTING
SURFACE CONDITION
• Cleanliness
• Colour
• Texture
PHYSICAL CONDITIONS
• Specimen Condition – Shape and Size – Temperature
ENVIRONMENTAL FACTORS –– Humidity and Temperature
MENTAL ATTITUDE
FATIGUE

28. APPLICATIONS OF VISUAL INSPECTION
 It is used to inspect whether there is a misalignment of
parts in the equipment
 It checks for corrosion, erosion, cracks and deformities
of machine components
 It inspect the plant components for any leakage or
abnormal operation
 It is used to identify the defects in weldments

29. PART - A
1. When the non destructive testing methods are used? Why?
2. Give the importance of using NDT.
3. List out limitations of NDT methods
4. Name the defects that can be detected by visual inspection
PART - B
1. Explain the following
2. (i) Applications of visual inspection
3. (ii) Advantages and disadvantages of visual inspection.
4. Illustrate the various optical aids used in visual inspection
techniques.
QUESTIONS