Shape ShiftersSMART MATERIALS

SHAPE MEMORY ALLOYS INTELLIGENT MATERIALS

Adaptive materials

Introduction

• The Material which has a capability to retain it’s original shape at transition temperature even after severe disturbance is known as smart material.

• They have Pseudo elasticity and Shape memory effect properties.

Discovery

• In 1932 ,Arne Olander a swedish physicist discovered this phenomenon in Au-Cd alloy

Types• Piezoelectric: converts mechanical stress into

electric current example: piezoelectric microphones • Shape memory: after deformation these materials

can retain it’s original shape example: shape memory stents(blood clot filter)

• Thermochromic: change color in response to change in temperature. Example: bath plugs

• Photochromic: change color in response to change in light . Example: security ink

• Magnetorheological :these fluids become solid when placed in a magnetic field

Piezo-electric materials

Thermochromic materials

Photochromic materials

Magnetorheological Fluids

• The MR fluid is liquid as shown on the left, when no magenetic field is present, but turns solid immediately after being placed in a magnetic field on the right.

SMART MATERIALS

SHAPE MEMORY ALLOYS

INTELLIGENT MATERIALS

Examples

• Ni – Ti

• Ni – Mn –Ga

• Cu – Zn – Al

• Au – Cd

• Cu – Al - Ni

PropertiesShape Memory Effect

• SME occurs due to the change in the crystalline structure

of materials.

Two phases are

Martensite(low temperature phase ,relatively weak) and Austenite (high temp phase, relatively strong)

..

Types ofShape memory effect (SME)

One-Way SME

Materials which return to it’s original shape by heating only .

Two-Way SME

Materials which return to it’s original shape by heating and recooling.

• Phase Phase transformationtransformation

• Martensite – Martensite – Lower strength, Lower strength, increased ductilityincreased ductility

• Austenite- Higher Austenite- Higher strength, strength, decreaseddecreased ductilityductility

Pseudo-elasticity

• The ability of SMA to return to it’s original shape upon unloading after a substantial deformation is known as Super elasticity or Pseudo elasticity.

Thermal Hysteresis

• Martensite to Austenite transformation occurs by heating .

• Austenite to Martensite occurs by cooling.

• Ms-Martensite start• Mf-Martensite finish• As-Austenite start • A f-Austenite finish

APPLICATIONS• Engineering, Industry and Military :

In Structural health monitoring used as a sensor

Used in reducing electronic and food waste, retractable antenna ,fine tuned helicopter blades,electrical connectors, and microvalves.

• Health : Bio Sensors- to monitor blood sugar level,Microsurgical instruments, Dental archwires,Implant devices, blood clot filters, eye glass frame.

Bone Plates, Screws

Bone plates & Screws

SMA polymer

Nitinol Cloth

Smart Fabric

• Smart fabric is used to sense temperature and chemicals

Toys & Novelties

EYE GLASS FRAME

Aerospace Dynamics

Home Appliances

• Rice cookerSMA spring opens the pressure control valve at the certain temperature, and releases excess steam to outside.

• Coffee makerSMA spring releases hot water when boiled to pour it over the coffee beans.

• Air conditioner for heating and coolingSMA spring changes the direction of louver to upward when cooling and downward when heating.

Merits

• Bio-compatibility

• Simplicity ,compactness and safety mechanism

• Good mechanical properties

Demerits

• More expensive

• Low energy efficiency

• Complex control

• Limited bandwidth

Thank You