L20 thermography principles

1. M.KARTHIKEYAN
ASSISTANT PROFESSOR
DEPARTMENT OF MECHANICAL ENGINEERING
AAA COLLEGE OF ENGINEERING & TECHNOLOGY, SIVAKASI
karthikeyan@aaacet.ac.in
ME8097 NON DESTRUCTIVE TESTING
AND EVALUATION

2. UNIT III THERMOGRAPHY AND EDDY CURRENT TESTING
(ET)
1. Thermography- Principles,
2. Contact and non contact inspection methods,
3. Techniques for applying liquid crystals, Advantages and
limitation
4. Infrared radiation and infrared detectors, Instrumentations and
methods, applications.
5. Eddy Current Testing-Generation of eddy currents, Properties
of eddy currents,
6. Eddy current sensing elements, Probes,
7. Instrumentation,
8. Types of arrangement,
9. Applications, advantages, Limitations,
Interpretation/Evaluation.

3. THERMOGRAPHY TESTING
INTRODUCTION:
 Thermography is a non-contact, non-destructive testing method.
 Used in the aerospace, defense and general engineering
industries to detect flaws in a variety of structures.
 Thermographic inspection can be used over a large area.
 Can detect a range of defects, including: Voids, Delaminations,
Corrosion, Porosity, Crack Propagation and Impact Damage.

4. TYPE 1
Every object with a temperature above the absolute zero point
(-273 °C) will emits infrared (IR) radiation.
But the human eye cannot identify this infrared (IR) radiation
due to its wavelength.

5.  Thermal imager can detect this IR.
 Its central element, the detector, is sensitive to IR radiation.
 Based on the intensity of the IR radiation, it determines the
temperature of the object's surface, and makes it visible for the
human eye with a thermal image.
 This process is referred to as thermography.
THERMAL IMAGER

6.  In order to make the IR radiation visible, the detector records
it, converts it into an electric signal, and gives each signal a
certain colour which is then shown in the display of the thermal
imager.
 In principle, thermal imagers thus translate wavelengths from
the infrared spectrum into wavelengths which are visible to the
human eye (colours).
INFRA RED
THERMOMETER

9. TYPE 2
 The basic principle of thermographic NDT is that the flow of
heat from the surface of a solid is affected by internal flaws
such as disbonds, voids or inclusions.

10. TYPES
1. PULSED OR FLASH THERMOGRAPHY TEST
2. LOCKIN – THERMOGRPAHY
3. BURST VIBRO THERMOGRAPHY
4. LOCK IN VIBRO RHERMOGRAPHY

11. PULSED OR FLASH THERMOGRAPHY TEST

12. PULSED OR FLASH THERMOGRAPHY TEST

13.  Pulse thermography is a non-destructive technique used to find
defects in aircraft and aerospace components.
 Pulse thermography allows materials to be inspected very
quickly for near-surface defects and bonding weaknesses.
 In pulse thermography the material to be inspected is heated
up equally using a very short heat pulse.
 Defects, bonding faults and corrosion can be observed using a
thermographic camera on the surface.

14. LOCKIN - THERMOGRPAHY

15. LOCK IN VIBRO RHERMOGRAPHY
SONIC WAVES – DEFECT – DISTURB
– VIBRATION ENERGY INTO HEAT

16. BURST VIBRO THERMOGRAPHY
SONIC WAVES – DEFECT – DISTURB
– VIBRATION ENERGY INTO HEAT

17. ADVANTAGES
 Large areas can be scanned fast.
 Thermography is an area investigating technique, whereas
most of the other non-destructive methods are either point or
line testing methods.
 This results in major savings in time, people, work and
machinery.
 Thermographic device is risk-free, as it does not emit any
radiation;
 It shows a visual picture so temperatures over a large area can
be compared
 It is capable of catching moving targets in real time.

18.  It is possible to predict the failure by observing the
temperature.
 It can be used to measure or observe in areas inaccessible or
hazardous for other methods.
 IR cameras are relatively easy to use.
 Large electrical cabinets and whole electrical installations can
be quickly scanned.
 The exact location of the potential problematic point can be
easily determined.

19. LIMITATIONS
 It is not possible to penetrate in extended depths (only a few
mm's).
 To interpret the results requires a certain experience and
knowledge.
 Quality cameras often have a high price range

20. APPLICATIONS:
 They are used by the police and military for night vision,
surveillance, and navigation aid;
 by firemen and emergency rescue personnel for fire
assessment, and for search and rescue;
 by the medical profession as a diagnostic tool; and
 preventative maintenance,
 processes control and
 nondestructive testing.

21.  defects in composite
 It can be used to find defects in shafts, pipes, and other metal
or plastic parts.
 It can be used to detect objects in dark areas.
 It is capable of catching moving targets in real time.
 It is possible to predict the failure by observing the
temperature.
 It can be used to measure or observe in areas inaccessible or
hazardous for other methods.
 Used in the aerospace, defense and general engineering
industries to detect flaws in a variety of structures.
 Can detect a range of defects, including: Voids, Delaminations,
Corrosion, Porosity, Crack Propagation and Impact Damage.

22. Typical problems in electrical installations that can be detected
with infrared thermography include:
 Connections that are loose, poorly installed, corroded etc.
 Unbalanced loads.
 Defective equipment.
 Undersized conductors.
 Overheated motors.
 Overloaded circuits.
 Potential fire hazards.
 Worn components.
 Thermal abnormalities in batteries.

23. Infrared Thermography is ..
1. a graphical representation of heat
2. an accurate measurement of temperature
3. a photographic representation of heat
MCQ - 1

24. Every object with a temperature above …….. will emits
infrared (IR) radiation.
1. 0°C
2. 300°C
3. 100°C
4. -273 °C
MCQ - 2

25. Wavelength of the is infrared (IR) radiation is
1. 550 nanometer
2. 580 nanometer
3. 600 nanometer
4. 450 nanometer
MCQ - 3

26. Ultrasonic waves are used in case of
1. LOCKIN – THERMOGRPAHY
2. PULSED OR FLASH THERMOGRAPHY
3. VIBRO THERMOGRAPHY
MCQ - 4

27. Infrared thermometer is superior to thermal imager
1. True
2. False
MCQ - 5

28. PART - A
1. Define thermography
2. What are the applications of thermography test?
PART - B
1. What are the methods available for checking in thermography?
Explain any one method
QUESTIONS