This presentation discusses smart materials and shape memory alloys. It introduces smart materials as materials that can change their properties in response to external stimuli like stress, temperature, electric or magnetic fields. Shape memory alloys are a type of smart material that remembers their original shape and can recover their shape by heating after being deformed. Common shape memory alloys include nickel-titanium and copper-based alloys. They undergo a phase change from martensite to austenite in response to temperature that enables their shape memory effect and superelasticity. The presentation covers the properties, advantages, and applications of shape memory alloys.

1. SMART MATERIALS & SHAPE MEMORY ALLOYS
PRESENTATION BY : ABIN ABRAHAM

2. SMART MATERIALS
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3. INTRODUCTION
 Smart materials are the materials that can significantly alter one or more of their inherent properties
owing to the application of an external stimuli in a controlled fashion.
 The several external stimulus to which the SMART Materials are sensitive are :
Stress
Temperature
Moisture
pH
Electric Fields
Magnetic Fields
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4. PROPERTIES
 Sensing materials and devices.
 Actuation materials and devices.
 Control devices and techniques.
 Self detection , Self diagnostic.
 Self corrective , self controlled , self healing.
 Sock absorbers , damage arrest.
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5. CLASSIFICATION
SMART MATERIALS
Piezoelectric Electrostrictive Magnetostrictive Thermoelectric Shape memory photochromic
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6. PIEZOELECTRIC MATERIALS
 When subjected to an electric charge
or a variation in voltage, piezoelectric
material will undergo some
mechanical change, and vice versa.
These events are called the direct and
converse effects.
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7. MAGNETOSTRICTIVE MATERIALS
 When subjected to a magnetic
field, and vice versa (direct and
converse effects), this material
will undergo an induced
mechanical strain. Consequently,
it can be used as sensors and/or
actuators.
(Example: Terfenol-D.)
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8. ELECTROSTRICTIVE MATERIALS
 This material has the same
properties as piezoelectric
material, but the mechanical
change is proportional to the
square of the electric field. This
characteristic will always
produce displacements in the
same direction.
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9. THERMORESPONSIVE MATERIALS
 Thermoresponsive is the ability
of a material to change
properties in response to
changes in temperature. They
are useful in thermostats and
in parts of automotive and air
vehicles.
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10. SHAPE MEMORY ALLOYS
 SME occurs due to the change in the
crystalline structure of materials.
 Two phases are:
1.Martensite:
• Low temperature phase
• Relatively weak
2. Austenite:
• High temperature phase
• Relatively strong
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11. SELF HEALING POLYMERS
 Self-healing materials are a class of smart materials
that have the structurally incorporated ability to
repair damage caused by mechanical usage over
time. The inspiration comes from biological systems,
which have the ability to heal after being wounded.
 The different strategies of designing self-healing
materials are as follows:
• release of healing agent
• reversible cross-links
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12. SELF HEALING POLYMERS
 RELEASE OF HEALING AGENTS :
1. HOLLOW FIBER REPAIR MECHANISM
2. MICROENCAPSULATED HEALING AGENT.
3. MICRO VASCULAR NETWORK.
 REVERSIBLE CROSS-LINKS :
1. DIELS-ALDER AND RETRO DA REACTIONS.
2. LONOMERS.
3. SUPRAMOLECULAR POLYMERS.
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13. MERITS & DEMERITS
MERITS
 Bio-compactibility.
 Simplicity.
 Compactness.
 Safety mechanism.
 Good mechanical properties.
DEMERITS
 More expensive.
 Low energy efficiency.
 Complex control.
 Limited bandwidth.
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14. APPLICATIONS
 Aircrafts.
 Orthopedic surgery.
 Dental braces.
 Robotics.
 Reducing vibration of
helicopter blades.
 Smart fabrics.
 Sporting goods.
 Smart glass.
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15. SHAPE MEMORY ALLOYS
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16. INTRODUCTION
 Shape Memory Alloys are materials
that “remember” their original shape.
 SMA a is one of the type of smart
materials.
 If deformed, they recover their original
shape upon heating.
 They can take large stresses without
undergoing permanent deformation.
 They can be formed into various
shapes like bars, wires, plates and
rings thus serving various functions.
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17. HOW DOES IT WORK?
 SMAs shape changes based on a solid state phase transformation.
 The transition from one form of crystalline structure to another creates the mechanism
by which the shape change occurs in SMAs. This change involves transition from a
monoclinic crystal form (martensitic) to an ordered cubic crystal form (austenite).
 It consists of two main phases:
1. Austenite : High temperature phase 2.Martensite : Low temperature
phase
Cubic crystal structure. Monoclinic crystal
structure.
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18. TYPES OF SHAPE MEMORY ALLOYS
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NI-Ti alloys are more expensive to melt and
produced than copper alloy, but they are
preferred for their corrosion resistance,
biocompatibility, and higher electrical resisting
for resistive heating in actuator application.

19. CHARACTERISTICS Shape memory effect: Is based on martensitic phase transformation taking place without
diffusion. Martensitic phase transformation that occurs as a result of stress or temperature
change.
 Two types of shape memory behavior : 1)One-way shape memory: Transformation to the
desired shape occurs only upon heating, i.e., memory is with the austenite phase. 2)Two-
way shape memory: The deformed shape is remembered during cooling, in addition to the
original shape being remembered during heating, i.e., memory is with both austenite and
martensitic phases.
 Superelasticity shape memory (Pseudoelasticity): 1) It is an elastic (reversible) response to an
applied stress. Occurs without temperature change. 2) This property allows the SMA’s to
bear large amounts of stress without undergoing permanent deformation. 3) Temperature of
SMA is maintained above transition temperature. 4) Load is increased until austenite
transforms to martensitic. 5) When loading is decreased, martensitic transforms back of
austenite. 6) SMA goes back to original shape as temperature is still above transition
temperature.
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20. PROPERTIES
 The copper-based and Ni-Ti-based shape-memory alloys are
considered to be engineering materials.
 These compositions can be manufactured to almost any shape
and size.
 The yield strength of shape-memory alloys is lower than that of
conventional steel, but some compositions have a higher yield
strength than plastic or aluminum.
 The yield stress for Ni Ti can reach 500 MPa.
 The maximum recoverable strain these materials can hold
without permanent damage is up to 8% for some alloys.
 This compares with a maximum strain 0.5% for conventional
steels.
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21. ADVANTAGES
 Very high power/weight ratio comparatively
 Accessible voltages can accomplish Thermo
elastic transformation
 Higher strain recovery
 Higher strength
 Compactness, allowing for reduction in overall
actuator size.
 Noiseless and silent operation
 High corrosion resistance
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22. APPLICATIONS
 To reduces engine noise, some designers installs chevrons onto
engines to mix the flow of exhaust gases and reduces engine
noise.
 Recently, a prosthetic hand was introduced by Loh et al. that
can almost replicate the motions of a human hand.
 SMAs find a variety of applications in civil structures such as
bridges and buildings. One such application is Intelligent
Reinforced Concrete (IRC), which incorporates SMA wires
embedded within the concrete.
 Another application is active tuning of structural natural
frequency using SMA wires to dampen vibrations.
 Stent- A reinforced grafts for vascular application to replace or
repair damaged arteries (25mm diameter).
 The first consumer commercial application was a shape-
memory coupling for piping, e.g. oil line pipes for industrial
applications, water pipes.ABIN ABRAHAM 22

23. THANK YOU
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