ABSTRACT

Smart or intelligent materials are materials that have the intrinsic and extrinsic capabilities, first, to respond to stimuli and environmental changes and, second, to activate their functions according to these changes. The stimuli could originate internally or externally. Since its beginnings, materials science has undergone a distinct evolution: from the use of inert structural materials to materials built for a particular function, to active or adaptive materials, and finally to smart materials with more acute recognition, discrimination and reaction capabilities. To encompass this last transformation, new materials and alloys have to satisfy a number of fundamental specifications. Smart materials can come in a variety of sizes, shapes, compounds, and functions. But what they all share— indeed what makes them “smart”—is their ability to adapt to changing conditions. Smart materials are the ultimate shape shifters. They can also alter their physical form, monitor their environment, and even diagnose their own internal conditions. They can also do all of this while intelligently interacting with the objects and people around them. The components of the smart materials revolution have been finding their way out of the labs and into industrial applications for the past decade.
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CONTENTS

1. INTRODUCTION
2. USES & APPLICATIONS
3. SMART MATERIALS AND SMART SYSTEMS FOR THE FUTURE
4. SMART STRUCTURES
5. MILITARY APPLICATIONS
6. THE POTENTIAL BENEFITS
7. STRUCTURAL APPLICATION OF SMART MATERIALS
8. CONCLUSION



1. INTRODUCTION

1. 1 SMART MATERIALS

Over the past century, we have learned how to create specialized materials that meet our specific needs for strength, durability, weight, flexibility, and cost. However, with the advent of smart materials, components may be able to modify themselves, independently, and in each of these dimensions. Smart materials can come in a variety of sizes, shapes, compounds, and functions. But what they all share— indeed what makes them “smart”—is their ability to adapt to changing conditions. Smart materials are the ultimate shape shifters. They can also alter their physical form, monitor their environment, and even diagnose their own internal conditions. They can also do all of this while intelligently interacting with the objects and people around them. More boldly, it is highly likely that once smart materials become truly ubiquitous—once they are seamlessly integrated into a webbed, wireless, and pervasive network —smart materials will challenge our basic assumptions about, and definitions of “living matter.”



A smart fluid developed in labs at the Michigan Institute of Technology


IMPORTANCE

In certain respects, smart materials are an answer to many contemporary problems. In a world of diminishing resources, they promise increased sustainability of goods through improved efficiency and preventive maintenance. In a world of health and safety threats, they offer early detection, automated diagnosis, and even self-repair. In a world of political terrorism, they may offer sophisticated biowarfare countermeasures, or provide targeted scanning and intelligence- gathering in particularly sensitive environments. In general, smart materials come in three distinct flavors: passively smart materials that respond directly and uniformly to stimuli without any signal processing; actively smart materials that can, with the help of a remote controller, sense a signal, analyze it, and then “decide” to respond in a particular way; and finally, the more powerful and autonomous intelligent materials that carry internal, fully integrated controllers, sensors, and actuators.



2. USES & APPLICATIONS

The components of the smart materials revolution have been finding their way out of the labs and into industrial applications for the past decade. As yet, they fall into several classes and categories: piezoelectrics, electrorestrictors, magnetorestrictors, shape-memory alloys, and electrorheological fluids. What these materials all have in common is the ability to act as both sensors and actuators. In some cases, when a force is applied to these smart materials, they “measure” the force, and “reverse” the process by responding with, or creating, an appropriate counter force. In other cases, the materials are populated by sensors that detect environmental conditions within the material itself. When conditions cross designated thresholds, the materials then send a signal that is processed elsewhere in the system. For instance, “smart concrete”—under development at the State University of New York at Buffalo—would be programmed to sense and detect internal hairline fissures. If these conditions are detected, the smart material would alert other systems to avoid a structural failure. Smart materials are currently used for a growing range of commercial applications, including noise and vibration suppression (noise-canceling headphones); strain sensing (seismic monitoring of bridges and buildings); and sensors and actuators (such as accelerometers for airbags). A number of companies, including The Electric Shoe Company and Compaq, are also exploring the use of smart materials. The Electric Shoe Company is currently producing piezoelectric power systems that generate electric power from the body’s motion while walking. Compaq is investigating the production of special keyboards that generate power by the action of typing. Descriptions of applications for the smart materials mentioned above suggest that their impact will be broadly felt across industries.

Piezoelectrics

Piezoelectric materials produce an electrical field when subject to a mechanical strain. Conversely, if an electrical field is applied to them, the material is stressed. Thus they can be used to generate low levels of power from simple mechanical motions or to deform surfaces in response to electrical signals. An excellent example of this is the application of smart materials in snow skis. Piezoelectric elements adjust the stiffness of the skis in response to conditions on the slope by damping shock and optimizing performance throughout a run.

Magnetorestrictors

These materials behave much like piezoelectrics, in that they are reciprocal devices that can both “receive” and “send” information within the systems that they inhabit. However, unlike piezoelectrics, magnetorestrictors respond to a magnetic field rather than an electric field. As such, they produce a magnetic field when strained. Applications for magnetorestrictors include machine tools, transducers, and sonar systems. Magnetorestrictors can also be used for vibration control (in factory equipment or automobiles), fuel injection systems, and the reconditioning (relining) of aged water and sewer pipelines.

Shape Memory Alloys (SMAs)

This special class of adaptive materials can convert thermal energy directly into mechanical work. For example, smart shape memory alloys can be “pro- Institute for the Future grammed” to adopt a specific shape when the alloy reaches a designated temperature (say, 100º Fahrenheit). This same alloy can then be manipulated or mechanically deformed to adopt a different shape when not in this designated temperature (say, when the material is at 50º Fahrenheit). In turn, when the alloy is heated above a critical transition temperature (approaching 100º), the material will “remember” its earlier shape and restore it—effectively converting the heat into mechanical work. Alternatively, SMAs can be trained to exhibit two shape-memory effects. In this case, heating the SMA results in one memorized shape while cooling results in a second, different shape (manipulation could then occur at a third, variable temperature).Shape Memory Alloys are currently used in various military applications. For instance, vibration-dampening SMAs, when deployed on supersonic fighter planes, decrease irrational stresses on materials, thereby increase the life and viability of the aircraft. SMAs can also be used preventively, to sense when materials are reaching critical failure limits. Commercially, SMAs can be used for vibration dampening effects on various factory machinery—say, within a component that holds a die-cutting laser. In this case, the drop in vibration interference radically increases the laser’s accuracy. SMA devices could also enhance fire detection equipment, or any other component or situation in which a change in temperature could trigger a necessary mechanical action. Of particular interest is potential application in surgical situations where device longevity, simplicity (ease of use), and biocompatibility could all be benefited.

Electrorheological Fluids

These materials represent fluid suspensions—emulsions wherein the smart material is dispersed, though not dissolved, within a liquid solution. When subjected to an electrical field, these suspensions experience reversible changes in rheological properties such as viscosity, plasticity, and elasticity. These reversible changes take place because of controllable interactions that occur between various micron-sized “smart-particles” suspended within the emulsion. Looking to the automotive industry, commercial advances in smart hydraulic fluids, networked car suspension systems, and smart shock-absorbers are already in development. Applying the above described interactions to, say, the smart shock-absorber, a sensor at the front of the car detects variations in the road surface. That signal is sent to a processor that determines whether the shock absorber should be more or less stiff. By altering the electrical field in the shock absorber, the viscosity of the ER fluid inside is also changed, tuning the suspension within milliseconds to match road conditions. Technological applications have been proposed for ER fluids in automotive clutches and d valves, servo drives, dampers, and brakes.

2.1 FUTURE INNOVATIONS

Consumer applications of smart materials in the coming decade will emphasize comfort and safety: noise Canceling (headphones and car interiors) as well as vibration canceling applications (car suspension systems) will no doubt be early winners, with some products already in the market. Industrial applications will provide increased control, consistency, and efficiency of distributed processes (for example, the management of print production at multiple international sites from a single, central location). In both cases, the magic of the materials will be largely behind-the-scenes and invisible to all but the engineers who design and maintain the systems. In the short term, smart-material adaptation will play out primarily as simple sensor-actuator responses to environmental stimuli. In the longer term, as the technology evolves, materials that self-diagnose and self-repair will find applications in everything from very small biomedical materials (internal components may someday automatically clean your arteries when necessary, or alert you of an oncoming bout of the flu), to very large-scale building materials that provide economies and efficiencies in an increasingly resource-constrained world. Another potential breakout in this technology is the use of deformable materials to create tactile user interfaces. Such developments may come in the form of flat-screen components (a flat screen that is both display and keyboard combined) that work in tandem with the subject matter they present. For instance, as you sit at your screen-unit an d page link to your online banking accounts, unique keys that are context sensitive will beckon, raising up from the deformable screen surface, allowing you to perform specified commands and functions. As the task changes, so will the keys that present themselves.

The big commercial growth area for smart materials over the next decade is likely to be actively smart materials supported by a wireless infrastructure. This type of system will enable remote analysis and control of a wide range of sensors and actuators in many different environments. In some cases, these systems will be used to avoid sending workers into hazardous environments, but in others companies will deploy actively smart materials because they will be cost-effective. By decade’s end, intelligent materials will be routinely deployed in biomedical, military, and space applications. In these latter fields, it’s likely that the costs of innovation, and subsequent diffusion of the technology, will be subsidized by Government. Also by the end of the decade, watch for consumer markets in security and health applications to really come to the fore. Smart materials may act as sensors in these applications, notifying connected systems of abnormalities. Today’s relatively heavy heart monitor provided by cardiologists simply records signals for later analysis: smart materials will be capable of both sensing and transmitting anomalies in real time, thereby facilitating emergency response and treatment. Current military applications also hint at future possibilities for commercial applications.

Smart armoring of tanks, designed to diffuse the impacts of missiles, suggests strategies for shipping containers that protect their contents against damage. “Smart dust,” a new intelligence-gathering tool that employs a cloud of thousands of networked, floating camera-sensors (each “mote” is one millimeter square), spearheaded by Kris Pister and Randy Katz at University of California at Berkeley, hints at the future development of sensor arrays that could be deployed and utilized in environments that are hostile or dangerous to humans (such as the radioactive core of a nuclear reactor). Developers.


3. SMART MATERIALS AND SMART SYSTEMS FOR THE FUTURE

Smart systems trace their origin to a field of research that envisioned devices and materials that could mimic human muscular and nervous systems. The essential idea is to produce non-biological systems that will achieve the optimum functionality observed in biological systems through emulation of their adaptive capabilities and integrated design. By definition, smart materials and smart structures — and by extension smart systems — consist of systems with sensors and actuators that are either embedded in or attached to the system to form an integral part of it. The system and its related components form an entity that will act and react in a predicted manner, and ultimately behave in a pattern that emulates a biological function. The human body is the ideal or ultimate smart system. One of the first attempts to use the smart materials technology involved materials constructed to do the work of electromechanical devices. Since then, many types of sensors2 and actuators3 have been developed to measure or excite a system.

This technology is still in its infancy and the scientific community is just beginning to scratch the surface of its potential. With a bit of imagination one can see enormous benefits to society. This paper presents a simple overview of the technology. After defining what is meant by ‘smart materials’, it describes a smart structure and its components, and provides a few examples. This is part of an ongoing work on the use of smart materials for applications in engineering. A more detailed insight into smart structures and their applications is given elsewhere4. Today the drive to innovation is stronger than ever. Novel technologies and applications are spreading in all fields of science. Consequently, expectations and needs for engineering applications have increased tremendously, and the prospects of smart technologies to achieve them are very promising. Figure 1 summarizes these inter-relationships.



3.1 NEW MATERIAL REQUIREMENTS

To achieve a specific objective for a particular function or application, a new material or alloy has to satisfy specific qualifications related to the following properties

 technical properties, including mechanical characteristics such as plastic flow, fatigue and yield strength; and behavioral characteristics such as damage tolerance and electrical, heat and fire resistance
 technological properties, encompassing manufacturing, forming, welding abilities, thermal processing, waste level, workability, automation and repair capacities, economic criteria, related to raw material and reduction costs, supply expenses and availability
 environmental characteristics, including features such as toxicity and pollution; and sustainable development criteria, implying reuse and recycling capacities. If the functions of sensing and actuation are added to the list, then the new material/alloy is considered a smart material.










4. SMART STRUCTURES

As described earlier, a smart structure is a system that incorporates particular functions of sensing and actuation to perform smart actions in an ingenious way. The basic five components of a smart structure are summarized as follows (Figure 2):
Data Acquisition (tactile sensing): the aim of this component is to collect the required raw data needed for and appropriate sensing and monitoring of the structure.
Data Transmission (sensory nerves): the purpose of this part is to forward the raw data to the local and/or central command and control units.
Command and Control Unit (brain): the role of this unit is to manage and control the whole system by analyzing the data, reaching the appropriate conclusion, and determining the actions required.
Data Instructions (motor nerves): the function of this part is to transmit the decisions and the associated instructions back to the members of the structure.
Action Devices (muscles): the purpose of this part is to take action by triggering the controlling devices units.


DATA ACQUISITION

The sensing components of a smart structure are designed according to the nature of the event to be sensed radiation, magnetic, thermal, mechanical or chemical as well as according to the nature of the output required, such as thermal, magnetic, electrical, optical or mechanical. Other features considered are the size, geometry and mechanical properties of the required interface; the type of the environmental condition,such as corrosion, thermal, magnetic or electrical and, finally, the operational properties of the collected data such as sensitivity, bandwidth, linearity, gauge length, range. Fibre optics is an excellent example of sensors.

FIBRE OPTIC SENSING

Fibre optics is used as sensors that duplicate the action of conventional strain gauges. They respond to a change in transmitted light. This change could be in intensity, phase, frequency, polarization, wavelength or mode. They are highly sensitive, can detect minuscule variations and thus work very well. Three types of sensors are available: The Intensiometric type responds to any perturbation such as bending or twisting that changes the intensity of the transmitted light. These phase sensors come in a number of configurations and are highly sensitive to strains. The Michelson and Mach-Zehnder types use two fibers, one to sense and one as reference. They can measure strain over lengths in the order of meters. The Fabry-Perot type, which employs a single Fibre and reflectors, is based on the interference of light between two closely spaced surfaces. The Bragg grating type exploits spectroscopy, which is based on the modulation in the index of refraction along a short length of the fibers.. Figure 3 presents in a schematic way, a section of a smart bridge8.


ACTUATING COMPONENT

Like the sensing component, the actuating components are designed according to the nature of the required actuation — optical, magnetic, thermal, mechanical or chemical — as well as according to the nature of the driving energy, such as thermal, magnetic, electrical or chemical. Here also, environmental considerations such as thermal, magnetic or electrical properties sand corrosion, as well as the size, geometry and mechanical properties of the interface have to be considered. Finally, the properties of the actuators such as displacement, force generation, hysteretic, response time and bandwidth are also specified appropriately. Actuation can be produced by controlling devices such as actuators, pumps, heaters and dampers, and by a number of new materials such as those described previously.

SENSORS AND ACTUATORS

For active noise control applications, microphones are used as acoustic sensors and loudspeakers as acoustic actuators. For displacement and velocity control, two types of transducers are convenient: Linear Variable Differential Transformers (LVDT) and Linear Variable Inductance Transformers (LVIT). Other devices are also available— accelerometers and two basic types of actuators. Hydraulic and pneumatic actuators are employed when low frequency, large force and displacements are required, while the electromagnetic/ shaker types are utilized to react against an inertial electrodynamics mass.

COMMAND AND CONTROL UNIT

The command and control unit is the manager of day-to-day operations, responsible for monitoring the health and integrity of the system by means of a communication network which works in real time. The unit operates by controlling a compendium of integrated non-destructive evaluation instruments, by managing optical fibre sensors and actuators, or by overseeing operational and control devices. This is the brain of the smart structure and has two basic and distinct functions. The Processing Function. This function receives information; analyses it; sorts, arranges and classifies it; and stores and/or processes it depending on the nature, frequency and quality of the data and its origins. All these previous operations are dealt with by intelligent or smart processing, with or without human intervention, and with little or no human interaction. Special algorithms can be used to control the behavior or detect damage. Pattern recognition algorithms, as well as neural networks with fuzzy logic can be efficiently employed to process the raw data. Finally, expert systems can handle the retrieval, management, classification, and storage of the data. The Analysis Function. This function deals with the detailed examining of the raw data in an intelligent way. Using the analysis outlined above, it will exploit the results to assess the condition of the structure. This analysis consists of localizing and identifying specific variables, items or features as compared to threshold levels defined in advance, or specified in codes, rules, regulations or standards. When an adverse condition is detected and the appropriate corresponding conclusion is reached, decisions for action are sent to the action controlling devices, which will be triggered to react. Special algorithms are developed to operate these functions.

A FEW EXAMPLES

Vibration reduction in sporting goods. A new generation of tennis rackets, golf clubs, baseball bats(Figure 4) and ski boards have been introduced to reduce the vibration in these sporting goods, increasing the user’s comfort and reducing injuries.


Noise reduction in vehicles. Filaments of piezoelectric ceramic Fibre shaped into various geometries are used in conventional fabric or material processing to counter noise in vehicles, neutralizes shaking in helicopter rotor blades, or nullifies or at least diminishes vibrations in air conditioner fans and automobile dashboards. Spatial High Accuracy Position Encoding and Control System (SHAPECONS) incorporates smart components that were developed for the STEAR-9 Program (Figure 5).





5. MILITARY APPLICATIONS

There are number of distinctly military applications for the use of smart materials and smart systems can be delineated, among them:

Smart Skin. In battle soldiers could wear a T-shirt made of special tactile material that can detect a variety of signals from the human body, such as detection of hits by bullets. It can then signal the nature of the wound or injury, analyze their extent, decide on the urgency to react, and even takes some action to stabilize the injury.
Smart Aircraft. Figure 6 presents a few potential locations for the use of smart materials and structures in aircraft.
Autonomous Smart systems. Ground, marine or space smart vehicles will be a feature of future battles. These carriage systems, whether manned or unmanned, and equipped with sensors, actuators and sophisticated controls, will improve surveillance and target identification and improve battlefield awareness.
Stealth Applications. The smart vehicles mentioned above could be constructed using stealth technologies for their own protection: the B-2 stealth bomber or the F-117 stealth fighter is good examples of this technology. And, just as important, smart systems are needed for rapid and reliable identification of space or underwater stealth targets. The identification and detection of such targets, as well as the subsequent decision to take action with or without operator intervention, is another potential application of smart systems.


6. THE POTENTIAL BENEFITS

The potential future benefits of smart materials, structures and systems are amazing in their scope. This technology gives promise of optimum responses to highly complex problem areas by, for example, providing early warning of the problems or adapting the response to cope with unforeseen conditions, thus enhancing the survivability of the system and improving its life cycle. Moreover, enhancements too many pro ducts could provide better control by minimizing distortion and increasing precision. Another possible benefit is enhanced preventative maintenance of systems and thus better performance of their functions. By its nature, the technology of smart materials and structures is a highly interdisciplinary field, encompassing the basic sciences — physics, chemistry, mechanics, computing and electronics — as well as the applied sciences and engineering such as aeronautics and mechanical engineering. This may explain the slow progress of the application of smart structures in engineering systems, even if the science of smart materials is moving very fast.



7. STRUCTURAL APPLICATION OF SMART MATERIALS
The development of durable and cost effective high performance construction materials and systems is important for the economic well being of a country mainly because the cost of civil infrastructure constitutes a major portion of the national wealth. To address the problems of deteriorating civil infrastructure, research is very essential on smart materials. This paper highlights the use of smart materials for the optimal performance and safe design of buildings and other infrastructures particularly those under the threat of earthquake and other natural hazards. The peculiar properties of the shape memory alloys for smart structures render a promising area of research in this field.
7.1 MATERIALS AND APPLICATION
Shape Memory Alloys (SMA)
The term shape memory refers to the ability of certain alloys (Ni – Ti, Cu – Al – Zn etc.) to undergo large strains, while recovering their initial configuration at the end of the deformation process spontaneously or by heating without any residual deformation .The particular properties of SMA’s are strictly associated to a solid-solid phase transformation which can be thermal or stress induced. Currently, SMAs are mainly applied in medical sciences, electrical, aerospace and mechanical engineering and also can open new applications in civil engineering specifically in seismic protection of buildings.
Its properties which enable them for civil engineering application are
1. Repeated absorption of large amounts of strain energy under loading without permanent deformation. Possibility to obtain a wide range of cyclic behaviour –from supplemental and fully recentering to highly dissipating-by simply varying the number and/or the characteristics of SMA components.
2. Usable strain range of 70%
3. Extraordinary fatigue resistance under large strain cycles
4. Their great durability and reliability in the long run.
Structural Uses
1. Active control of structures
The concept of adaptive behavior has been an underlying theme of active control of structures which are subjected to earthquake and other environmental type of loads. The structure adapts its dynamic characteristics to meet the performance objectives at any instant. A futuristic smart bridge system (An artist rendition) is shown below :Fig.1 (3)
(Courtesy: USA Today dt. 03.03.97). Sun and Sun (6) used a thermo mechanical approach to develop a constitutive relation for bending of a composite beam with continuous SMA fibers embedded eccentric to neutral axis. The authors concluded that SMA’s can be successfully used for the active structural vibration control. Thompson et al (3) also conducted an analytical investigation on the use of SMA wires to dampen the dynamic response of a cantilever beam constrained by SMA wires.

Fig.1
2) Passive control of structures
Two families of passive seismic control devices exploiting the peculiar properties of SMA kernel components have been implemented and tested within the MANSIDE project (Memory Alloys for New Seismic Isolation and Energy Dissipation Devices). They are Special braces for framed structures and isolation devices for buildings and bridges.
3) Smart Material Tag
These smart material tag can be used in composite structures. These tags can be monitored externally through out the life of the structure to relate the internal material condition. Such measurements as stress, moisture, voids, cracks and discontinuities may be interpreted via a remote sensor
4) Retrofitting
SMAs can use as self-stressing fibers and thus they can be applied for retrofitting. Self-stressing fibers are the ones in which reinforcement is placed into the composite in a non-stressed state. A prestressing force is introduced into the system without the use of large mechanical actuators, by providing SMAs. These materials do not need specialized electric equipments nor do they create safety problems in the field. Treatment can be applied at any time after hardening of the matrix instead of during its curing and hardening. Long or short term prestressing is introduced by triggering the change in SMAs shape using temperature or electricity.
5) Self-healing
Experimentally proved self-healing behavior which can be applied at a material micro level widens their spectrum of use. Here significant deformation beyond the first crack can be fully recovered and cracks can be fully closed.
6) Self-stressing for Active Control
Can be used with cementations fiber composites with some prestess, which impart self-stressing thus avoiding difficulties due to the provision of large actuators in active control which require continuous maintenance of mechanical parts and rapid movement which in turn created additional inertia forces. In addition to SMA’s some other materials such as polymers can also be temporarily frozen in a prestrained state that have a potential to be used for manufacturing of self-stressing cementitious composites .

7) Structural Health Monitoring
Use of piezo transducers, surface bonded to the structure or embedded in the walls of the structure can be used for structural health monitoring and local damage detection. Problems of vibration and UPV testing can be avoided here. Jones et. al., applied neural networks to find the magnitude and location of an impact on isotropic plates and experimented using an array of piezo-transducers surface bonded to the plate.

Substitute for steel?
It is reported that (4) the fatigue behaviour of CuZnAl-SMA’s is comparable with steel.If larger diameter rods can be manufactured. It has a potential for use in civil engineering applications. Use of Fibre reinforced plastics with SMA reinforcements requires future experimental investigations.
CARBON FIBRE REINFORCED CONCRETE(CFRC)
Its ability to conduct electricity and most importantly, capacity to change its conductivity with mechanical stress makes a promising material for smart structures .It is evolved as a part of DRC technology(Densified Reinforced Composites).The high density coupled with a choice of fibers ranging from stainless steel to chopped carbon and kelvar, applied under high pressure gives the product with outstanding qualities as per DRC technology. This technology makes it possible to produce surfaces with strength and durability superior to metals and plastics.
SMART CONCRETE
A mere addition of 0.5%specially treated carbon fibres enables the increase of electrical conductivity of concrete. Putting a load on this concrete reduces the effectiveness of the contact between each fibre and the surrounding matrix and thus slightly reduces its conductivity. On removing the load the concrete regains its original conductivity. Because of this peculiar property the product is called “Smart Concrete”. The concrete could serve both as a structural material as well as a sensor.
The smart concrete could function as a traffic-sensing recorder when used as road pavements. It has got higher potential and could be exploited to make concrete reflective to radio waves and thus suitable for use in electromagnetic shielding. The smart concrete can be used to lay smart highways to guide self steering cars which at present follow tracks of buried magnets. The strain sensitive concrete might even be used to detect earthquakes.
Active railway track support
Active control system for sleepers is adopted

to achieve speed improvements on existing bridges and to maintain the track in a straight and non-deformed configuration as the train passes With the help of optimal control methodology the train will pass the bridge with reduced track deflections and vibrations and thus velocity could be safely increased. Fig(3) shows various positions of the train with and without active railway track support.
Active structural control against wind
Aerodynamic control devices to mitigate the bi-directional wind induced vibrations in tall buildings are energy efficient, since the energy in the flow is used to produce the desired control forces. Aerodynamic flap system(AFS) is an active system driven by a feedback control algorithm based on information obtained from the vibration sensors(3).The area of flaps and angular amplitude of rotation are the principal design parameters. fig.(4) shows an active aerodynamic control device.










8. CONCLUSION

Today, the most promising technologies for lifetime efficiency and improved reliability include the use of smart materials and structures. Understanding and controlling the composition and microstructure of any new materials are the ultimate objectives of research in this field, and is crucial to the production of good smart materials. The insights gained by gathering data on the behaviors of a material’s crystal inner structure as it heats and cools, deforms and changes, will speed the development of new materials for use in different applications.

Structural ceramics, superconducting wires and nonstructural materials are good examples of the complex materials that will fashion nanotechnology. New or advanced materials to reduce weight, eliminate sound, reflect more light, and handle more heat will lead to smart structures and systems which will definitively enhance our quality of life. It has wide range of applications in various fields. This seminar deals with the smart materials and its applications.

REFERENCES


• Autumn 2000 _ Canadian Military Journal

• The AMPTIAC Quarterly, Volume 7, Number 2

• J.Holnicki-szulc and J.Rodellar(eds), Smart Structures.,3.High Technology-Vol.65