Magnetostriction along with Production, Properties, and Application of ultrasonic waves.

1. MAGNETOSTRICTION AND
APPLICATIONS OF
ULTRASONIC WAVES
15Z204 - MATERIALS SCIENCE
Presented by
Pranav Shankar Ramalingam - 17Z230
Preethi.S.V - 17Z231
Priyadarshini.S -17Z232

2. Outline
In this Presentation, we will be discussing the
following :
• What is Magnetostriction?
• Working and Result of Magnetostriction.
• What are ultrasonic waves?
• Production of ultrasonic waves by
magnetostrsiction method.
• Properties of ultrasonic waves.
• Applications of ultrasonic waves (in the fields of
science, engineering, medicine, etc).

3. What is Magnetostriction?
• Magnetostriction is a property of ferromagnetic
materials that causes them to change their
shape or dimensions (expand or contract)
during the process of magnetization.
• The effect was first identified in 1842 by James
Joule when observing a sample of nickel.

4. Magnetostriction - Working
• Internally, ferromagnetic materials have
a structure that is divided into domains,
which are randomly oriented when the
material is not exposed to a magnetic
field and each domain is a region of
uniform magnetic polarization.
• When a magnetic field is applied, the
boundaries between the domains shift
and the domains rotate; both of these
effects cause a change in the material’s
dimensions.

5. Result of Magnetostriction
• The orientation of these small
domains by the imposition of the
magnetic field creates a strain field.
• As the intensity of the magnetic field is
increased, more and more magnetic
domains orientate themselves so that
their principal axes of anisotropy are
collinear with the magnetic field in
each region and finally saturation is
achieved.

6. Effect of increasing and
decreasing applied or
external magnetic field(H)
on a ferromagnetic
material can be seen
here.
The arrow mark indicates the change
in value (increase or decrease) and
direction of applied magnetic field.

7. Ultrasonic waves
The sound waves are classified into three
types on the basis of their frequencies.
They are namely
• (i) infrasonic waves (sound waves of
frequency below 20 Hz)
• (ii) audible sound waves (sound waves of
frequency between 20 and 20kHz)
• (iii) ultrasonic waves (sound waves of
frequency above 20kHz). Ultrasonic Waves

8. Production of Ultrasonic waves
The Ultrasonic waves are produced by a mechanical method using Galton's whistle.
It is also produced by magnetostriction and piezoelectric oscillators. Let us discuss
the magnetostriction oscillator in this section.
MAGNETOSTRICTION METHOD
To produce ultrasonic waves of frequencies up to 3MHz only.
• PRINCIPLE :
• The Magnetostriction oscillator is based on the principle of magnetostriction
effect.
• When a ferromagnetic material is subjected to a varying magnetic field, the length
of the ferromagnetic rod changes and the ferromagnetic rod is set into resonant
vibration, whenever the frequency of the tank circuit coincides with the vibration of
the ferromagnetic rod.

9. • CONSTRUCTION :
• A ferromagnetic rod AB made up of Ni is
clamped in the middle, C as shown.
• Coil of wires L1 and L2 are winded at the
ends of A and B.
• One end of the coil L2 is connected to the
base of an NPN transistor and the other
end of the coil L1 is connected to the
emitter and the negative terminal of a
battery.
• A variable capacitor C1 is connected
across the coil L1.
• One end of the variable capacitor is
connected to the collector circuit, whereas
the other end of the variable capacitor is
connected to the positive end of the
battery through a milliammeter and a key
K.
Production of Ultrasonic waves
Magnetostriction oscillator

10. Working - Magnetostriction Oscillator
• When the key is closed, the tank circuit (LC circuit) is set into oscillation
with a frequency of vibration given by
F= 1/(2π√(LC))
where L1 =inductance of coil L1 and C1 =capacitance of the capacitor
C1.
• An alternating EMF is produced due to the vibration of the tank circuit.
• This alternating EMF induces an alternating magnetic field.
• The length of the ferromagnetic material gets changed due to the
alternating magnetic field.
• The change in the length of the ferromagnetic material induces an EMF
in the coil L2.

11. • The induced emf is fed into the base of the transistor and hence it gets
amplified and it is fed into the tank circuit.Thus the oscillation is
continuously maintained.
• The frequency of the oscillation of the tank circuit is varied by adjusting the
variable capacitance value.
• If the frequency of the tank circuit matches with the frequency of vibration
of the ferromagnetic rod, ultrasonic waves are produced and the ultrasonic
waves are emitted from the ends of the rod as shown in the diagram. The
frequency of ultrasonic waves produced is given by
• Where l is the length of the ferromagnetic material, Y is the Young’s
modulus and ρ is the density of the ferromagnetic material.
Working - Magnetostriction Oscillator

12. Properties of Ultrasonic waves
• The frequency of the Ultrasonic waves is greater than 20 kHz.
• The Ultrasonic waves are highly energetic. Because of their high frequency,
they have intensity up to 10 kW(m)^-2.
• Like ordinary sound waves, Ultrasonic waves produce alternate compression
and rarefaction, when they are propagating through liquid and gaseous
medium.
• Ultrasonic waves produce Cavitation effect in liquids.
• The speed of the ultrasonic wave increases with the increase in its frequency.
Ultrasonic waves are having a shorter wavelength.
• The Ultrasonic waves exhibit reflection and interference phenomenon similar
to ordinary light waves.
• The Ultrasonic waves exhibit negligible diffraction effects.

13. Applications of Ultrasonic waves
• Science and engineering :
• 1. It is used to detect flaws or
cracked in metals.
• 2.It is used to detect ships,
submarines, iceberg etc, in ocean.
• 3. It is used for soldering aluminium
coil capacitors, aluminium wires
and plates without using any fluxes.
• 4. It is used to weld some metals
which can’t be welded by electric or
gas welding.
Ultrasonic Welding
Submarine-detection

14. Applications of Ultrasonic waves
• 5. It is used to cutting and drilling
holes in metals.
• 6. It is used to form stable
emulsion of even immiscible
liquids like water and oil or water
and mercury which finds
application in the preparation of
photographic films, face creams
etc.
• 7. It act like a catalytic agent and
accelerate chemical reactions.
Ultrasonic homogenizers
for liquid processing

15. • Medicine :
• 8. It is used to remove kidney stones and
brain tumours without shedding any blood.
• 9. It is used to remove broken teeth.It is also
used in cavitation. Ultrasonic cavitation is a
simple procedure that relies on sound waves
to flush fat from the body instead of intensive
surgery.
• 10. It is used for sterilising milk and to kill
bacteria.
• 11. It is used to study the blood flow
velocities in blood vessels of our body.
• 12. It is used as a diagnostic tool to detect
tumours, breast cancer and also the growth
of foetus can be studied.
Applications of Ultrasonic waves

16. Applications of Ultrasonic waves
• 13. A Cheap Ultrasonic Range Finder
Working - Everybody knows the
speed of the sound in the dry air is
around 340 m/s. Send a short
ultrasonic pulse at 40 kHz in the air,
and try to listen to the echo. Of
course you wont hear anything, but
with an ultrasonic sensor the back
pulse can be detected. If you know
the time of the forth & back travel of
the ultrasonic wave, you know the
distance, divide the distance by two
and you know the range from the
ultrasonic sensor to the first obstacle
in front of it.
Ultrasonic water depth detector