Ultrasonics.

1. ULTRASONICS
•NAME- MAYANK SHARMA
•BRANCH- CIVIL
•YEAR- 1ST YEAR
•GANGA INSTITUTE OF TECHNOLOGY AND MANAGEMENT

2. ULTRASONICS

3. CONTENTS
• Definition of ultrasonic
• Properties of ultrasonic
• Ultrasonic production
• Piezo-electric effect
• Applications of Ultrasonic

4. DEFINITION OF ULTRASONICS
ULTRASONICS is made up of two
words “ULTRA”meaning BEYONDand
“SONICS” meaning SOUND.
Sound waves in which the frequencies
are above the limits of human audibility
i.e. > 20 KHz are called
ULTRASONICS.

5. SPECTRUM OF SOUNDWAVES
Frequency Description Example
>20 Hz INFRASOUND EARTHQUA
KES
20Hz-20KHz AUDIBLE SOUND MUSIC
<20 KHz ULTRASONICS BAT

6. PROPERTIES OF ULTRASONICS
• They have a large energy content.
• They can be transmitted over long
distances without appreciable loss of
energy.
• Velocity of ULTRASONIC waves
depends on the temperature and
frequency of the medium.
• Just like ordinary waves , ULTRASONIC
waves get Reflected , Refracted and
Absorbed.

7. ULTRASONICSPRODUCTION
ULTRASONICS can be produced by the
following methods :
(1)Piezo-electric Generator
(2)Thermal Detection
(3) Sensitive flame method

8. PIEZO ELECTRICEFFECT
• If mechanical pressure is applied to the
opposite faces of crystal , equal and
opposite electrical charges appear across
its other faces .This is known as Piezo-
electric effect.
• Potential Difference developed would
be proportional to pressure applied.
• The converse of Piezo-electric effect is also
True.
• This effect was best observed in
Quartz , Tourmaline etc.

10. PRINCIPLE
If mechanical pressure is
applied to the opposite
faces of the crystal ,
potential difference is
developed ,which would
be proportional to the
pressure applied .

11. PIEZO-ELECTRIC
GENERATOR
• THE QUARTZ CRYSTAL
IS PLACED BETWEEN
TWO METAL PLATESA
AND B.
• THE PLATES ARE
CONNECTED TO THE
PRIMARY (L3) OF A
TRANSFORMER.
• THE COILS L1 AND L2 OF
OSCILLATOR
CIRCUIT ARE TAKEN
FROM THE
SECONDARY OF A
TRANSFORMER.
• THE COLLECTOR COIL
L2 IS INDUCTIVELY
COUPLED TO BASE
COIL L1.

12. WORKINGOF THE GENERATOR
(1)When battery is switched on, the
oscillator produces high frequency
alternating voltages with a frequency.
(2)Due to the transformer action, an
oscillatory
e.m.f. is induced in the coil L3. This high
frequency alternating voltages are fed on
the plates A and B.

13. (3) INVERSEPIEZO-ELECTRIC EFFECTTAKESPLACE
AND THE CRYSTAL CONTRACTS AND EXPANDS
ALTERNATIVELY
(4) The frequency of the vibration is
given by
ρ =density of the crystal.
n
= Y=Young’sModulus.
(5) The variable condenser C1 is
adjusted such that the frequency of
the applied voltage is equal to the
natural frequency of the crystal, and
thus resonance takes place.

14. THERMAL DETECTION
• THIS KIND OF DETECTION IS BASEDON CHANGE IN RESISTANCE DUE TO
HEATING. IN A THERMAL DETECTOR A FINEPLATINUM WIREFIXEDAT
BOTH ENDS IS USED. IT IS PLACEDIN THE REGION TO BE TESTEDFOR
ULTRASONIC. THE WIREBEGINS TO VIBRATE RAPIDLY CAUSING HEATING
AND COOLING ALTERNATELY AT THE NODES AND ANTINODES. THE
RESISTANCE OF WIREALSO CHANGES ACCORDINGLYWHICH IS
DETECTEDBY SUITABLE ARRANGEMENTS TO CONFIRM PRESENCE OF
ULTRASONICS.

16. SENSITIVE FLAME METHOD
•A NARROW FLAME IS MOVED ALONG THE MEDIUM WHERE THE
PRESENSE OF ULTRASONICS IS EXPECTED. AT AN ANTINODE THE
FLAME DEVELOPS SUDDEN FLICKERS, BECAUSE THERE IS A CHANGE IN
PRESSURE.THIS METHOD CAN BE ALSO BE USED TO DETERMINE
VELOCITY AND WAVELENGTH OF ULTRASONICS.

17. APPLICATIONS OF ULTRASONIC WAVES
• Detection of flaws(cracks ,blowholes,
porosity) in metals .
• In SONAR (SOund Navigation And
Ranging).
• Ultrasonic welding.
• Ultrasonic cutting and machining.
• Ultrasonic soldering.