L30 TRANSDUCERS

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 IV ULTRASONIC TESTING (UT) AND ACOUSTIC
EMISSION (AE)
1. Ultrasonic Testing-Principle,
2. Transducers,
3. Transmission and pulse-echo method,
4. Straight beam and angle beam,
5. Instrumentation,
6. Data representation, A/Scan, B-scan, C-scan.
7. Phased Array Ultrasound, Time of Flight Diffraction.
8. Acoustic Emission Technique – Principle,
9. AE parameters, Applications

3. TRANSDUCER
 Transducer converts the electrical energy to acoustic energy
and vice versa.
 The transducer performs both the sending and the receiving of
the acoustic energy.

4. TYPES
1. CONTACT TRANSDUCERS
2. PAINT BRUSH TRANSDUCERS
3. ANGLE BEAM TRANSDUCERS
4. NORMAL INCIDENCE SHEAR WAVE TRANSDUCERS
5. DELAY LINE TRANSDUCERS
6. DUAL ELEMENT TRANSDUCERS
7. IMMERSION TRANSDUCERS

5. CONTACT TRANSDUCERS
 Contact transducers are used for direct contact inspections, and
are generally hand manipulated.
 These transducers have an ergonomic design so that they are
easy to grip and move along a surface.
 They often have replaceable wear plates to increase their life.
 Coupling materials of water, grease, oils, or commercial
materials are used to remove the air gap between the transducer
and the component being inspected.

6. PAINT BRUSH TRANSDUCERS
 Paint brush transducers are used to scan wide areas more
rapidly for discontinuities.
 These long and narrow transducers are made up of an array of
small crystals that are carefully matched to minimize variations
in performance and maintain uniform sensitivity over the entire
area of the transducer.

7. ANGLE BEAM TRANSDUCERS
 Angle beam transducers and wedges are typically used to
introduce a refracted shear wave into the test material.
 Transducers can be purchased in a variety of fixed angles or in
adjustable versions.
 The angled sound path allows the sound beam to be reflected
from the backwall to improve detectability of flaws in and
around welded areas.

8. NORMAL INCIDENCE SHEAR WAVE TRANSDUCERS
 Normal incidence shear wave transducers are unique because
they allow the introduction of shear waves directly into a test
piece without the use of an angle beam wedge.

9. DELAY LINE TRANSDUCERS
 As the name implies, the primary function of a delay line
transducer is to introduce a time delay between the generation
of the sound wave and the arrival of any reflected waves.
 This allows the transducer to complete its "sending" function
before it starts its "listening" function so that near surface
resolution is improved.
 They are designed for use in applications such as high precision
thickness gauging of thin materials and delamination checks in
composite materials.

10. DUAL ELEMENT TRANSDUCERS
 Dual element transducers contain two independently operated
elements in a single housing.
 One of the elements transmits and the other receives the
ultrasonic signal.
 Dual element transducers are very useful when making
thickness measurements of thin materials and when inspecting
for near surface defects.

11. IMMERSION TRANSDUCERS
 Immersion transducers do not contact the component.
 These transducers are designed to operate in a liquid
environment and all connections are watertight.
 Immersion transducers are typically used inside a water tank.

12. ADVANTAGES
 High penetrating power, which allows the detection of deep
flaws
 High sensitivity, permitting the detection of extremely small
flaws.
 Greater accuracy
 Some capability of estimating the size, orientation, shape and
nature of defects.
 Some capability of estimating the structure of alloys of
components with different acoustic properties
 Non-hazardous
 Capable of portable or highly automated operation.
 Results are immediate. Hence on the spot decisions can be
made.

13. DISADVANTAGES
 Requires careful attention by experienced technicians.
 Extensive technical knowledge is required for the development
of inspection procedures.
 Parts that are rough, irregular in shape, very small or thin, or
not homogeneous are difficult to inspect.
 Cleaning of surface is required
 Couplants are needed to provide effective transfer of ultrasonic
wave energy between transducers and parts being inspected
unless a non-contact technique is used.

14. 1. Basically sound waves are ______________
a) Voltage signals
b) Pressure waves
c) Current
d) Radiation
MCQ - 1

15. Why does the Ultrasonic Sensor have two openings in the
front ?
1. One opening is for sending out the sound waves and One
opening is for receiving the returning sound waves
2. It is necessary for the robot to see where it is going
3. A bat has two eyes to see better so the robot needs two
eyes as well
4. Just for decoration purposes.
MCQ - 2

16. Sounds of frequency higher than 20,000 Hz which are
inaudible to normal human ear are called
1. noise
2. frequency
3. ultrasonic
4. amplitude
MCQ - 3

17. SONAR is the abbreviation of
1. small navigation and random
2. sky navigation and ranging
3. sun nuclear ranging
4. sound navigation and ranging
MCQ - 4

18. Ultrasonic waves carry more
1. energy only
2. frequency only
3. heat
4. energy and frequency
MCQ - 5