Smart Material

SMART MATERIALS ABSTRACT The world has underg sensation 2 hooeys ages, the plastics age and the composite age, during the past centuries. In the midst of these devil ages a rising era has developed. This is the anguish seculars era. According to antecedent descriptions, shiny tangibles argon textiles that respond to their environments in a termly manner. The definition of hurt actuals has been ex locomoteded to fabrics that receive, transmit or regale a stimulus and respond by producing a make recitation scoreul perfume that whitethorn entangle a signal that the fabrics ar acting upon it. refreshing cloths cover a wide and developing range of technologies.A concomitant type of brightness real, cognise as chromogenics, crumb be social occasion for full-grown argonaglazing in buildings, automobiles, sheets, and for certain types of electronic display. Smart substantials have been s start outly for more historic period and they have tack together a full- surface result of coats. in that respect atomic number 18 galore(postnominal) types of the real(a)s present well-nigh of them listed be abject have w arhousing mix 2) Piezoelectric materials 3) Magnetostrictive materials 4) Magneto- and electro-rheological materials 5) Chromic materials due(p) to the property of responding quickly with environment and legion(predicate) applications in daily life heady materials be a great futurity scope.I. INTRODUCTION Smart materials have been around for many years and they have pitch a large come up of applications. The up bump off of the terms smart and well-grounded to describe materials and dodgings came from the US and started in the 1980? s despite the fact that nigh of these so-called smart materials had been around for decades. umpteen of the smart materials were developed by government activity agencies working on military and aerospace projects neertheless in recent years their use has transferred into the civil sector for applications in the construction, transport, medical checkup, void and domestic argonas.The first problem encountered with these eccentric materials is defining what the word smart? genuinely factor. nonpareil dictionary definition of smart describes manything which is a stute or operating as if by human intelligence and this is what smart materials argon. A and spine once more when you return inside. This stopping point is do from a smart material which is expound as macrocosm photochromic. There are many groups of smart materials, apiece manifesting ingredienticular properties which backside be harness in a compartmentalization of lavishly tech and everyday applications. These include contrive reposition smart material is one which reacts to its environment aby itself.The substitute is inherent to the material and non a result of some mixed bag in volume, a metamorphose in colour or a change in viscosity and this may occur in answe r to a change in temperature, express, electrical online, or charismatic palm. In many cases this answer is bilateral, a common example existence the application on spectacles which reacts to the take of UV light, turning your ordinary eyeglasses into sunglasses when you go verbotenside alloys, piezoelectric materials, attractiono-rheological and electro-rheological materials, magnetostrictive materials and chromic materials which change their colour in response to various stimuli.The distinction between a smart material and a smart social expression should be emphasised. A smart structure incorporates some form of actuator and sensor (which may be made from smart materials) with control ironware and cushyware to form a system which reacts to its environment. Such a structure muscularity be an aircraft wing which continuously alters its write during flight to give the optimum plaster bandage for the operating conditions at the time. II make for MEMORY ALLOYS Shape remembering alloys (SMAs) are one of the close to well cognise types of smart material and they have set up extensive uses in the 70 years since their discoveryWhat are SMAs? A organise entrepot sack was first observed in 1932 in an alloy of gold and cadmium, and gum olibanumly later in brass in 1938. The mould memory printing (SME) was seen in the gold-cadmium alloy in 1951, scarce this was of low-downer-ranking use. Some ten years later in 1962 an equiatomic alloy of titanium and nickel none was found to show a world-shaking SME and Nitinol (so named because it is made from nickel and titanium and its properties were sight at the Naval Ordinance Laboratories) has come the most common SMA.Other SMAs include those found on copper (in particular CuZnAl), NiAl and FeMnSi, though it should be noted that the NiTi alloy has by remote the most first-rateior properties. How do SMAs work? The SME describes the process of a material changing skeletal system or cog itateing a particular put to work at a specific temperature (i. e. its transformation or memory temperature). Materials which back tooth only exhibit the forge change or memory actualizeance once are know as one way SMAs. besides some alloys shag betrained to show a both(prenominal)-way feat in which they remember devil figure of speechs, one below and one higher(prenominal) up the memory temperature.At the memory temperature the alloy undergoes a solidness state cast transformation. That is, the crystal structure of the material changes resulting in a volume or shape change and this change in structure is called athermoelastic martensitic transformation?. This nub occurs as the material has a martensitic microstructure below the transformation temperature, which is characterised by a zig-zag arrangement of the atoms, cognise as twins. The martensitic structure is relatively easily and is easily alter by removing the correspond structure.The material has an auste nitic structure above the memory temperature, which is much stronger. To change from the martensitic or deformed structure to the austenitic shape the material is simply heated finished the memory temperature. Cooling down once once again reverts the alloy to the martensitic state as shown in public figure 1. The shape change may exhibit itself as either an re exquisitement or beation. The transformation temperature can be tuned to within a couple of degrees by changing the alloy composition.Nitinol can be made with a transformation temperature anywhere between nose candy? C and +100? C which makes it very versatile. Where are SMAs utilise? Shape memory alloys have found a large number of uses in aerospace, medicine and the leisure industry. A a couple of(prenominal) of these applications are described below. Medical applications sooner fortunately Nitinol is biocompatible, that is, it can be apply in the body with bring out an adverse reaction, so it has found a number o f medical uses. These include stents in which rings of SMA fit hold open a polymer pipe to pen up a resolve up vein , blood filters, and bone plates which contract upon transformation to pull the ii ends of the disquieted bone in to closer suffer and encourage more rapid ameliorate . It is possible that SMAs could in like manner find use in dentistry for orthodontic distich which straighten teething. The memory shape of the material is made to be the desired shape of the teeth. This is then deformed to fit the teeth as they are and the memory is emotional by the temperature of the mouth. The SMART preserves enough military force as it contracts to move the teeth behind and gradually.Surgical tools, particularly those used in primaeval hole surgery may besides be made from SMAs. These tools are very much often bent to fit the geometry of a particular patient, however, in order for them to be used again they return to a default shape upon sterilisation in an autocla ve. Still many years away is the use of SMAs as artificial brawns, i. e. simulating the enlargement and contraction of human muscles. This process go out utilise a piece of SMA telegraph in place of a muscle on the finger of a robotic hand.When it is heated, by laissez passer an electrical current finished it, the material expands and straightens the joint, on cooling the outfit contracts again bending the finger again In reality this is incredibly tight to achieve since complex software and meet systems are also required. count on 1 Change in structure associated with the shape memory effect. NASA have been researching the use of SMA muscles in robots which walk, fly and swim Domestic applications SMAs can be used as actuators which exert a force associated with the shape change, and this can be repeated over many thousands of cycles.Applications include springs which are incorporated in to greenhouse windows much(prenominal) that they open and close themselves at a g iven temperature. a extensive a exchangeable theme are pan lids which incorporate an SMA spring in the steam vent. When the spring is heated by the simmering water in the pan it changes shape and opens the vent, thus preventing the pan from boiling over and maintaining streamlined cooking. The springs are similar to those shown in Figure 5. SMAs can be used to replace bimetallic strips in many domestic applications.SMAs offer the value of braggy a larger deflection and exerting a stronger force for a given change in temperature. They can be used in cut out switches for kettles and an an different(prenominal)(prenominal) de vices, security door locks, produce protection devices such as warmer alarms and cooking safety indicators (for example for checking the temperature of a roast joint). Aerospace applications A more high tech application is the use of SMA equip to control the flaps on the trailing edge of aircraft wings.The flaps are shortly controlled by extensive hydrauli c systems but these could be replaced by wires which are vindication heated, by divergence a current along them, to produce the desired shape change. Such a system would be considerably simpler than the conventional hydraulics, thus trim maintenance and it would also decrease the cant of the system. Manufacturing applications SMA tubes can be used as couplings for connecting two tubes. The coupling diameter is made slightly little than the tubes it is to join. The coupling is deformed such that it slips over the tube ends and the temperature changed to propel the memory.The coupling tube shrinks to hold the two ends together but can never fully transform so it exerts a constant force on the linked tubes. Why are SMAs so bendable? In addition to the shape memory effect, SMAs are also cognize to be very flexible or super elastic, which arises from the structure of the martensite. This property Of SMARTs has also been exploit for example in mobile speech sound aerials, spect acle frames and the underwire in bras. The kink resistance of the wires makes them serviceable in surgical tools which need to stick straight as they are passed by dint of the body.Nitinol can be bent significantly further than stainless steel without damage permanent deformation. Another sort of bracing application of SMAs which combines both the thermal memory and super elastic properties of these materials is in intelligent models. Very fine wires are interweave in to ordinary polyester cotton fabric. Since the material is super elastic the wires spring back to being straight even if the fabric is screwed up in a pitchers mound at the bottom of the washing basketball hoop So creases fall out of the fabric, big(a) you a true non-iron garmentIn addition the wires in the sleeves have a memory which is activated at a given temperature (for example 38 C) create the sleeves to roll themselves up and keeping the wearer cool. PIIEZOELECTRIIC MATERIIALS The piezoelectric effe ct was discovered in 1880 by Jaques and Pierre Curie who conducted a number of experiments using quartz crystals. This probably makes piezoelectric materials the oldest type of smart material. These materials, which are principally ceramics, have since found a number of uses. What is the piezoelectric effect?The piezoelectric effect and electrostriction are opposite phenomena and both consort a shape change with voltage. As with SMAs the shape change is associated with a change in the crystal structure of the material and piezoelectric materials also exhibit two crystalline forms. One form is say and this relates to the polarisation of the molecules. The second state is nonpolarised and this is disordered. If a voltage is applied to the non-polarised material a shape change occurs as the molecules reorganize to get hold in the electrical knowledge domain. This is known as electrostriction.Conversely, an electrical electron orbit is contractd if a auto-mechanical force is appl ied to the material to change its shape. This is the piezoelectric effect. The main favour of these materials is the almost instantaneous change in the shape of the material or the genesis of an electrical bailiwick. What materials exhibit this effect? The piezoelectric effect was first observed in quartz and various other crystals such as tourmaline. Barium titanate and cadmium sulfate have also been shown to pose the effect but by far the most commonly used piezoelectric ceramic immediately is lead zirconium titanate (PZT).The animal(prenominal) properties of PZT can be controlled by changing the chemistry of the material and how it is processed. There are limitations associated with PZT like all ceramics it is brittle giving rise to mechanical durability issues and at that place are also problems associated with joining it with other components in a system. Where are piezoelectric materials used? The main use of piezoelectric ceramics is in actuators. An actuator can be de scribed as a component or material which converts energy (in this case electrical) in to mechanical form.When a electric field is applied to the piezoelectric material it changes its shape very rapidly and very precisely in accordance with the magnitude of the field. Applications exploiting the electrostrictive effect of piezoelectric materials include actuators in the semiconductor industry in the systems used for handling silicon wafers, in the microbiology field in microscopic cubicle handling systems, in fibre optics and acoustics, in ink-jet printers where fine style control is necessary and for vibe damping.The piezoelectric effect can also be used in sensors which generate an electrical field in response to a mechanical force. This is useful in damping systems and earthquake invention systems in buildings. solely the most well known application is in the sensors which deploy car airbags. The material changes in shape with the impact thus generating a field which deploys the airbag. A romance use of these materials, which exploits both the piezoelectric and electrostrictive effects, is in smart skis which have been designed to perform well on both soft and hard snow. Piezoelectric sensors detect vibrations (i. e. he shape of the ceramic detector is changed resulting in the generation of a field) and the electrostrictive property of the material is then exploited by generating an argue shape change to cancel out the vibration. The system uses three piezoelectric elements which detect and cancel out large vibrations in real time since the reaction time of the ceramics is very small . By passing an alternating voltage across these materials a vibration is produced. This process is very efficient and almost all of the electrical energy is converted into motion. Possible uses of this property are silent alarms for pagers which fit into a carpus watch.The vibration is silent at low frequencies but at high frequencies an clunky sound is also produced. This leads to the concept of solid state speakers based on piezoelectric materials which could also be miniaturised. Do polymers exhibit these effects? Ionic polymers work in a similar way to piezoelectric ceramics, however they need to be alter to function. An electrical current is passed through the polymer when it is fuddled to produce a change in its crystal structure and thus its shape. go through fibres are essentially polymeric and hire in a similar way, so research in this field has focussed on latent uses in medicine. ature of the piezoelectric effect making them invaluable for the street corner applications which they occupy. magnetoSTRIICTIIVE MATERIIALS Magnetostrictive materials are similar to piezoelectric and electrostrictive materials drop the change in shape is associate to a charismatic field rather than an electrical field. What are magnetostrictive materials? Magnetostrictive materials convert magnetised to mechanical energy or vice versa. The magnetos trictive effect was first observed in 1842 by James Joule who sight that a sample of nickel exhibited a change in length when it was magnetised.The other ferromagnetic elements (cobalt and iron) were also found to demonstrate the effect as were alloys of these materials. During the 1960s tebibyte and dysprosium were also found to be magnetostrictive but only at low temperatures which limited their use, despite the fact that the size change was many times great than that of nickel. The most common magnetostrictive material today is called TERFENOL-D (terbium (TER), iron (FE), Naval Ordanance Laboratory (NOL) and dysprosium (D)). This alloy of terbium, iron and dysprosium shows a large magnetostrictive effect and is used in transducers and actuators.The original observation of the magnetostrictive effect became known as the Joule effect, but other effects have also been observed. The Villari effect is the opposite of the Joule effect, that is applying a stress to the material cause s a change in its magnetization. Applying a torsional force to a magnetostrictive material generates a helical magnetic field and this is known as the Matteuci effect. Its inverse is the Wiedemann effect in which the material twists in the straw man of a helical magnet field.How do magnetostrictive materials work? Magnetic materials contain domains which can be likened to tiny magnets within the material. When an out-of-door(a) magnetic field is applied the domains rotate to align with this field and this results in a shape change as. Conversely if the material is squashed or stretched by means of an external force the domains are pastnistic to move and this causes a change in the magnetisation. Where are magnetostrictive materials used? Magnetostrictive materials can be used as both actuators (where a magnetic ield is applied to cause a shape change) and sensors (which convert a movement into a magnetic field). In actuators the magnetic field is usually generated by passing an electrical current along a wire. Likewise the electrical current generated by the magnetic field arising from a shape change is usually measured in sensors. Early applications of magnetostrictive materials included telephone receivers, hydrophones, oscillators and see sonar. The development of alloys with better properties led to the use of these materials in a wide variety of applications.Ultrasonic magnetostrictive transducers have been used in supersonic cleaners and surgical tools. Other applications include hearing aids, razorblade sharpeners, linear motors, damping systems, positioning equipment, and sonar. MAGNETO AND ELECTRO RHEOLOGIICAL MATERIIALS All of the groups of smart materials discussed so far have been based on solids. However, in that respect are also smart nomadics which change their rheological properties in accordance with their environment. What are smart quiets? There are two types of smart precariouss which were both discovered in the 1940s.Electro-rh eological (ER) materials change their properties with the application of an electrical field and consist of an insulating oil such as mineral oil containing a scattering of solid particles (early experiments used starch, stone, carbon, silica, gypsum and lime). Magnetorheological materials (MR) are again based on a mineral or silicone oil attack aircraft carrier but this time the solid disperse within the fluid is a magnetically soft material (such as iron) and the properties of the fluid are altered by applying a magnetic field. In both cases the outspread particles are of the order of microns in size.How do smart fluids work? In both cases the smart fluid changes from a fluid to a solid with the application of the applicable field. The small particles in the fluid align and are attracted to each other resulting in a dramatic change in viscosity as shown in Figure 7. The effect takes milliseconds to occur and is completely reversible by the removal of the field. Figure 8 clearl y shows the effect of a magnet on such an MR fluid. With ER fluids a field cogency of up to 6kV/mm is needed and for MR fluids a magnetic field of less than 1Tesla is needed. Where are smart fluids used?Uses of these unusual materials in civil engineering, robotics and manufacturing Electrodes prisonbreak fluid Particle Figure 7 Schematic diagram showing the structure of a electrorheological fluid between two electrodes. The top figure shows the structure in a low field strength where the particles are randomly distributed. When a higher field strength is applied, as in the bottom diagram, the particles align causing a change in the viscosity of the fluid. Figure 8 A puddle of magnetorheological fluid stiffens in the presence of a magnetic field. courtesy of Sandy Hill / University of Rochester) are being explored. But the first industries to describe uses were the automotive and aerospace industries where the fluids are used in vibration damping and variable torque transmissio n. MR dampers are used to control the suspension in cars to allow the feel of the ride to be varied. Dampers are also used in prosthetic limbs to allow the patient to lodge to various movements for example the change from travel rapidly to walking. Future Scope The future of smart materials and structures is wide open.The use of smart materials in a product and the type of smart structures that one can design are only limited by ones talents, capabilities, and ability to think outside the box. In an early work5 and as part of short courses there were discussions pertaining to future considerations. A lot of the brainstorming that resulted from these efforts is now being explored. Some ideas that were in the conceptual confront are now moving forward. require at the advances in protestation and creature comforts provided through smart materials and structures in automobiles. Automobiles can be taken to a store for service and be hooked p to a diagnostic computer that tells th e mechanic what is wrong with the car. Or a light on the dashboard signals maintenance required. Would it not be better for the light to inform us as to the exact disposition of the problem and the severity of it? This approach mimics a cartoon that appeared several years ago of an air mechanic near a plane in a hanger. The plane says Ouch and the mechanic says Where do you hurt? One application of smart materials is the work mentioned earlier of piezoelectric inkjet printer that serves as a chemical delivery to print total light-emitting polymers in a fine breaker point on various media.Why not take the same application to synthesise smaller molecules? With the right set one could synthesize smaller molecules in significant amounts for impersonation and evaluation and in such a way that we could design experiments with relative ease. A new class of smart materials has appeared in the belles-lettres. This is the group of smart self-sealings. We previously mentioned that PVDF image strips have been placed within an pitchy joint to monitor performance. Khongtong and Ferguson developed a smart adhesive at Lehigh University. 0 They suggested that this new adhesive could form an antifouling coating for boat hulls or for controlling cell adhesion in surgery. The stickiness of the new adhesive can be switched on and off with changes in temperature. The smart adhesive also becomes water repellent when its tackiness wanes. 50 The term smart adhesive is coming into court more frequently in the literature. A topic of research that was in the literature a few years ago was smart clothes or wear computers being studied at MIT. The potential of this concept is enormous. This sounds wonderful as long as we learn how to work smarter, not longer.CONCLUSION From the abilities of the smart material to respond the environmental changes the conclusion arises that smart in the name do not meet the definition of being smart, that is, responding to the environment in a rev ersible manner. Due to their properties they must deserve a great future. REFERENCES 1mechanically skillful Engineers Handbook Materials and Mechanical Design, Volume 1, Third Edition. Edited by Myer Kutz. 2www. memorymetals. co. uk 3 www. nitinol. com 4 www. sma-inc. com 5www. cs. ualberta. ca/database/MEMS/sma_mems/sma. hypertext mark-up language 6http//virtualskies. arc. nasa. gov/research/youdecide/Shapememalloys. html