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SMART MATERIALSSMART MATERIALS AND ITS AND ITS

APPLICATIONS APPLICATIONS

BYBYG.S.RAGHAVENDRAG.S.RAGHAVENDRA

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IntroductionIntroduction

construction materials and systems construction materials and systems

• durable durable • cost effective cost effective • high performancehigh performance

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Smart materials

Smart materials are materials that have the intrinsic and extrinsic capabilities

firstly to respond to environmental changes and

secondly to activate their functions according to these changes.

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Smart Structure

Structure that incorporates smart materials

Perform particular functions like sensing, transmitting and recording of data.

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Components of a Smart StructureComponents of a Smart Structure

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Control systemControl system• monitors the sensor’s signalmonitors the sensor’s signal• processing the information in order to determine processing the information in order to determine

action required.action required.• If an action is required, then a signal is applied to If an action is required, then a signal is applied to

the appropriate actuator.the appropriate actuator.

SensorSensor• To monitor environmental changes To monitor environmental changes • and generate signals proportional to the changing and generate signals proportional to the changing

measured.measured.

ActuatorActuator• used to change the properties of the smart structure used to change the properties of the smart structure

in order to achieve the desired responsein order to achieve the desired response

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Smart structure aims at 5 basic function

Data Acquisition Data Transmission Command and control process Data instructions Action Device

CONTROL SENSORData

Transmission

Data

Transmission

ACTUATORS

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Classification Of Smart Materials Piezoelectric

Electrostrictive

Magnetostrictive

Optical fibers

Shape memory alloys

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Piezoelectric MaterialsPiezoelectric Materials

They have two unique properties which areThey have two unique properties which areinterrelated.interrelated.

When a piezoelectric material is deformed, it When a piezoelectric material is deformed, it gives off a small but measurable electrical gives off a small but measurable electrical discharge. discharge.

Alternately, when an electrical current is Alternately, when an electrical current is passed through a piezoelectric material it passed through a piezoelectric material it experiences a significant increase in size experiences a significant increase in size

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Illustration of the Piezoelectric EffectIllustration of the Piezoelectric Effect

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AdvantagesAdvantages Compact and light weight.Compact and light weight. Displacement proportional to applied voltage.Displacement proportional to applied voltage. Operate over large temperature range.Operate over large temperature range.

DisadvantagesDisadvantages Brittle due to crystalline structure.Brittle due to crystalline structure. Produce small strains compared to SMA and Produce small strains compared to SMA and

magnetostrictives.magnetostrictives. Cannot withstand high shear and tension.Cannot withstand high shear and tension.

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Electrostrictive and Magnetostrictive Electrostrictive and Magnetostrictive materialsmaterials

These are ferromagnetic materials These are ferromagnetic materials

Experience an elastic strain when subjected to Experience an elastic strain when subjected to an electric field and magnetic field respectively.an electric field and magnetic field respectively.

used in high precision actuation.used in high precision actuation.

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Shape memory alloys (SMA's)Shape memory alloys (SMA's)

Shape memory alloys are metals, which Shape memory alloys are metals, which exhibit two very unique properties,exhibit two very unique properties,

• pseudo-elasticitypseudo-elasticity, and, and• shape memory effectshape memory effect. .

1414SHAPE MEMORY ALLOYS

1515SHAPE MEMORY ALLOYS

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SHAPE MEMORY ALLOYS

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Crystal Structures Of SMA

The two phases which occur in shape memory The two phases which occur in shape memory alloys, are alloys, are

Martensite andMartensite and AusteniteAustenite

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MartensiteMartensite is the relatively soft and easily deformed phase of is the relatively soft and easily deformed phase of

shape memory alloys,shape memory alloys, which exists at lower temperatures. which exists at lower temperatures. It is stable in low energy level having a sheared It is stable in low energy level having a sheared

version of structure.version of structure.

AusteniteAustenite the stronger phase of shape memory alloys,the stronger phase of shape memory alloys, occurs at higher temperatures.occurs at higher temperatures. It is stable in high energy level with a It is stable in high energy level with a bccbcc

structure.structure.

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Pseudo-elasticityPseudo-elasticity

It is stress induced, phase transformation mechanism It is stress induced, phase transformation mechanism

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Shape Memory EffectShape Memory Effect

It is temperature induced, phase transformation It is temperature induced, phase transformation mechanismmechanism

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Properties of shape memory Alloys

Repeated absorption of large amount of strain energy

Usable strain range of 70%

Extraordinary fatigue resistance under large strain cycle

There great durability and reliability in the long run

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Structural uses

Active control of structures

Passive control of structures

Smart material tag

Retrofitting

Self healing

prestressing

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Active control of structuresconcept of adaptive behavior of smart materials

Test Setup of the Cantilevered Beam with SMA Wire Test Setup of the Cantilevered Beam with SMA Wire

Actuators, (Baz Actuators, (Baz et al.et al., 1990), 1990)

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Passive control of structures

special braces for framed structures

isolation devices for buildings and bridges

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Arrangement of SMA braces in framed model

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The Structure and the SMA Actuators (Shahin et al).The Structure and the SMA Actuators (Shahin et al).

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Smart Material Tag

Used in composite structures

Can be monitored externally throughout the life of the structure

The internal material conditions like moisture, voids, cracks may be interpreted via sensing.

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Retrofitting SMAs can be used as self stressing fibers and thus they can be applied for retrofitting

SMA tendons are placed into the composite in non stressed state

Prestressing force is introduced into the system by providing heating

Treatment can be applied at any time after hardening of the matrix

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Self-healing

The deformation beyond the first crack can be fully recovered and cracks can be fully closed.

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Smart prestressingSmart prestressing

prestressing concrete using shape memory alloy tendons

prestressing force in beams can be changed by using heat activated SMA tendons

Jacking equipment is not needed

it requires an electrical source of heat to trigger the tendons

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Other Applications Of Smart MaterialsOther Applications Of Smart Materials

Structural Health Monitoring

Monitoring can be done by the use of → piezo transducers, bonded to the surface of the structure → optical fibre composites in retrofitting

local damage detection can be done.

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Smart concreteAddition of 0.5% of carbon fibers enables the increase of electrical conductivity of concrete Addition of load reduces the conductivity of the concrete, on removing of load concrete regains its original conductivity Functions as a traffic sensing recorder when used as road pavement Used to lay smart highways to guide self steering cars which at present follow tracks of buried magnets

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Substitute for steel?

The fatigue behavior of CuZnAl- SMAs is comparable with steel

Larger diameter rods manufacture has potential for use in civil engineering applications

require future investigations

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ACTIVE RAILWAY TRACK SUPPORT

The train will pass the bridge with reduced track deflection and vibrations and thus velocity could be safely increased

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Active Structural Control Against Wind

Aerodynamic control devices reduces the bi-directional wind induced vibrations in tall buildings

Aerodynamic flap system (AFS) is an active system driven by a feed back control algorithm based on information obtained from the vibration sensors

3636ACTIVE AERODYNAMIC CONTROL DEVICE

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Smart building materials remove Smart building materials remove pollutantspollutants

These are special construction materials and These are special construction materials and coatings containing titanium dioxide (TiO2) coatings containing titanium dioxide (TiO2)

They can “capture” organic and inorganic air They can “capture” organic and inorganic air pollutants after they have been exposed to ultra-pollutants after they have been exposed to ultra-violet and/or sun rays. violet and/or sun rays.

The degraded polluting substances can then be The degraded polluting substances can then be washed away by rainwaterwashed away by rainwater..

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3939Flagpole in Dupont court

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Sensor box mounted on flag pole

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Flagpole in Dupont court 102-foot-tall

Outfitted with a specially designed system of sensors

These sensors provide measurements of the response of the structure to the wind

Monitoring station on top of Building.

Data from sensors is continuously transmitted to computers through wireless and wired connections.

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Rion Antirion Bridge,Greece

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The technologies using smart materials are useful for both new and existing constructions.

Of the many emerging technologies available the few described here need further research to evolve the design guidelines of systems. Codes, standards and practices are of crucial importance for the further development.

CONCLUSION

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