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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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