Smart Material

SMART MATERIALS ABSTRACT The world has undergone two temporals ages, the plastics age and the coordination compound age, during the past centuries. In the midst of these two ages a new eon has substantial. This is the yen hooeys era. According to early explanations, hurt fabrics atomic minute 18 bodilys that respond to their surroundingss in a dately manner. The definition of trendy materials has been expanded to materials that receive, transmit or process a stimulus and respond by producing a riding habitful accomplishment that whitethorn include a signal that the materials atomic number 18 playacting upon it. Smart materials coer a wide and developing range of technologies.A feature vitrine of brilliant material, know as chromogenics, disregard be practice session for large atomic number 18aglazing in buildings, automobiles, planes, and for certain types of electronic display. Smart materials carry been about for numerous years and they have imbed a la rge human body of performances. There argon many types of the materials present some of them listed below govern recollection alloy 2) piezoelectric materials 3) Magnetostrictive materials 4) Magneto- and electro- rheologic materials 5) Chromic materials Due to the prop of responding quickly with environment and many natural coverings in daily life apt materials deserve a great future scope.I. INTRODUCTION Smart materials have been around for many years and they have institute a large number of drills. The use of the terms sharp and reasoning(a) to describe materials and systems came from the US and started in the 1980? s despite the circumstance that some of these so-called smart materials had been around for decades. Many of the smart materials were developed by government agencies accomplishmenting on military and aerospace projects however in recent years their use has transferred into the civil sector for applications in the construction, transport, medical, empty and domestic argonas.The commencement ceremony job encountered with these unusual materials is defining what the word smart? actually means. One dictionary definition of smart describes something which is a stute or operating as if by human intelligence and this is what smart materials argon. A and indorse again when you return inside. This coating is made from a smart material which is set forth as macrocosm photochromic. There are many groups of smart materials, separately acquainting particular properties which house be harnessed in a variety of high-tech and everyday applications. These include see depot smart material is one which reacts to its environment aby itself.The shift is inherent to the material and not a result of some flip-flop in volume, a channelize in colour or a castrate in viscousness and this whitethorn occur in response to a change in temperature, form, galvanising current, or magnetic written report. In many subject areas this response i s two-sided, a common use being the coating on glasses which reacts to the level of UV light, turning your ordinary glasses into sunglasses when you go outside alloys, piezoelectric materials, magneto-rheological and electro-rheological materials, magnetostrictive materials and chromic materials which change their colour in reaction to several(a) stimuli.The distinction between a smart material and a smartstructure should be emphasised. A smart structure incorporates some row of actuator and sensor (which may be made from smart materials) with control hardware and software to form a system which reacts to its environment. Such a structure might be an aircraft wing which continuously alters its profile during flight to give the optimum get for the operating conditions at the time. II SHAPE MEMORY ALLOYS Shape memory alloys (SMAs) are one of the most swell known types of smart material and they have found extensive uses in the 70 years since their discoveryWhat are SMAs? A expl oit memory transformation was first observed in 1932 in an alloy of gold and compact disc, and then later in organization in 1938. The make for memory inwardness (SME) was seen in the gold-cadmium alloy in 1951, but this was of little use. Some ten years later in 1962 an equiatomic alloy of titanium and nickel was found to exhibit a important SME and Nitinol (so named because it is made from nickel and titanium and its properties were discovered at the Naval decree Laboratories) has become the most common SMA.Other SMAs include those ground on hair (in particular CuZnAl), NiAl and FeMnSi, though it should be noted that the NiTi alloy has by furthermost the most superior properties. How do SMAs work? The SME describes the process of a material ever-changing baffle or remembering a particular visualize at a specific temperature (i. e. its transformation or memory temperature). Materials which finish only exhibit the shape change or memory sumuate once are known as one commission SMAs. heretofore some alloys can betrained to show a two-way effect in which they remember two shapes, one below and one to a higher place the memory temperature.At the memory temperature the alloy undergoes a solid state phase transformation. That is, the vitreous silica structure of the material changes resulting in a volume or shape change and this change in structure is called athermoelastic martensitic transformation?. This effect occurs as the material has a martensitic microstructure below the transformation temperature, which is characterised by a zig-zag arrangement of the atoms, known as twins. The martensitic structure is relatively soft and is well misrepresented by removing the twinned structure.The material has an austenitic 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 by the memory temperature. chill down again reverts the all oy to the martensitic state as shown in habitus 1. The shape change may exhibit itself as either an involution or contraction. The transformation temperature can be tuned to inside a equal of degrees by changing the alloy composition.Nitinol can be made with a transformation temperature anywhere between 100? C and +100? C which makes it very versatile. Where are SMAs utilize? Shape memory alloys have found a large number of uses in aerospace, medicine and the leisure industry. A few of these applications are described below. Medical applications Quite fortunately Nitinol is biocompatible, that is, it can be apply in the body without an adverse reaction, so it has found a number of medical uses. These include stents in which rings of SMA telegraph hold open a polymer render to pen up a blocked vein , blood filters, and bone plates which contract upon transformation to curl up the two ends of the broken bone in to closer contact and come on more rapid healing . It is possible that SMAs could in like manner find use in dentistry for orthodontic braces which like a shoten teeth. 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 activated by the temperature of the mouth. The SMART exerts enough cart as it contracts to move the teeth late and gradually.Surgical tools, particularly those use in key hole surgery may in like manner be made from SMAs. These tools are often often hardening 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 autoclave. Still many years away is the use of SMAs as slushy muscles, i. e. simulating the expansion and contraction of human muscles. This process will utilise a piece of SMA wire in place of a muscle on the figure of a robotic hand.When it is heated, by passing an galvanising current through it, the material expands and straig htens the joint, on cooling the wire contracts again bending the finger again In reality this is incredibly difficult to achieve since knotty software and surrounding systems are also required. Figure 1 reposition 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 tell over many thousands of cycles.Applications include fountains which are incorporated in to greenhouse windows such that they open and close themselves at a given temperature. along a akin(predicate) theme are pan lids which incorporate an SMA spring in the steam vent. When the spring is heated by the b crude oiling water supply in the pan it changes shape and opens the vent, thus preventing the pan from boiling over and maintaining businesslike cooking. The springs are similar to those shown in Figure 5. SMAs can be used to replace bimetallic strips in many domestic applications.SMAs set up the advantage of gravid 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 other devices, security door locks, crowd out protection devices such as smoke alarms and cooking safety indicators (for utilisation for checking the temperature of a roast joint). Aerospace applications A more high tech application is the use of SMA wire to control the flaps on the trailing progress of aircraft wings.The flaps are currently controlled by extensive hydraulic systems but these could be replaced by wires which are resistance heated, by passing a current along them, to rear the desired shape change. Such a system would be considerably simpler than the conventional hydraulics, thus reducing forethought and it would also decrease the weight of the system. Manufacturing applications SMA tubes can be used as couplers for connecting two tubes. The coupling diameter is made slightly smaller than the tubes it is to join. The coupling is deformed such that it slips over the tube ends and the temperature changed to activate the memory.The coupling tube shrinks to hold the two ends together but can never amply transform so it exerts a constant force on the fall in tubes. Why are SMAs so flexile? In addition to the shape memory effect, SMAs are also known to be very flexible or super elastic, which arises from the structure of the martensite. This property Of SMARTs has also been exploited for mannequin in mobile phone aerials, spectacle frames and the underwire in bras. The kink resistance of the wires makes them helpful in surgical tools which regard to remain straight as they are passed through the body.Nitinol can be bent significantly further than spot slight steel without suffering permanent deformation. Another rather overbold application of SMAs which combines some(prenominal) the ther mal memory and super elastic properties of these materials is in intelligent fabrics. Very fine wires are woven in to ordinary polyester cotton fiber fabric. Since the material is super elastic the wires spring back to being straight even if the fabric is screwed up in a heap at the bottom of the washing basket So creases fall out of the fabric, giving 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) causing the sleeves to roll themselves up and keeping the wearer cool. PIIEZOELECTRIIC MATERIIALS The piezoelectric effect 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 mainly ceramics, have since found a number of uses. What is the piezoelectric effect?The piezoelectric effect and electrostriction are opposite phenomena and two relate 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 ordered and this relates to the polarisation of the molecules. The molybdenum state is nonpolarised and this is disordered. If a voltage is use to the non-polarised material a shape change occurs as the molecules reorganise to align in the electrical arena. This is known as electrostriction.Conversely, an electrical field is turn overd if a mechanical force is apply to the material to change its shape. This is the piezoelectric effect. The main advantage of these materials is the almost instantaneous change in the shape of the material or the contemporaries of an electrical field. What materials exhibit this effect? The piezoelectric effect was first observed in quartz and dissimilar other crystals such as tourmaline. Barium titanate and cadmium sulphate have also been shown to demonstrate the effect but by far the most commonly used piezoelectric ceramic straightaway is lead zirconium titanate (PZT).The physical 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 there 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 described as a component or material which change overs 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 use d for handling silicon wafers, in the microbiology field in microscopic cell handling systems, in fibre optics and acoustics, in ink-jet printers where fine movement control is necessary and for vibration damping.The piezoelectric effect can also be used in sensors which generate an electrical field in response to a mechanical force. This is reclaimable in damping systems and earthquake detection systems in buildings. But 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 novel use of these materials, which exploits both the piezoelectric and electrostrictive do, is in smart skis which have been knowing 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 opposing 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 alternate 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 unspoken alarms for pagers which fit into a wrist watch.The vibration is silent at low frequencies but at high frequencies an audible auditory sensation is also produced. This leads to the concept of solid state speakers found 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 wet to function. An electrical current is passed through the polymer when it is wet to produce a change in its crystal structure and thus its shape. pass fibr es are essentially polymeric and operate in a similar way, so research in this field has focussed on effectiveness uses in medicine. ature of the piezoelectric effect making them invaluable for the niche applications which they occupy. MAGNETOSTRIICTIIVE MATERIIALS Magnetostrictive materials are similar to piezoelectric and electrostrictive materials except the change in shape is link up to a magnetic field rather than an electrical field. What are magnetostrictive materials? Magnetostrictive materials convert magnetic to mechanical energy or vice versa. The magnetostrictive effect was first observed in 1842 by James Joule who noticed 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 sixties terbium and dysprosium were also found to be magnetostrictive but only at low temperatures which hold their use, despite the fa ct that the size change was many times greater than that of nickel. The most common magnetostrictive material directly 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 comment 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 causes 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 nominal head 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 outer 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 forced 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 include telephone receivers, hydrophones, oscillators and scanning sonar. The development of alloys with interrupt properties led to the use of these materials in a wide variety of applications.Ultrasonic magnetostrictive tra nsducers have been used in supersonic cleaners and surgical tools. Other applications include hearing aids, razorblade sharpeners, linear motors, damping systems, arrangement equipment, and sonar. MAGNETO AND ELECTRO RHEOLOGIICAL MATERIIALS All of the groups of smart materials discussed so far have been based on solids. However, there are also smart fluids which change their rheological properties in accordance with their environment. What are smart fluids? There are two types of smart fluids which were both discovered in the 1940s.Electro-rheological (ER) materials change their properties with the application of an electrical field and consist of an insulating oil such as mineral oil containing a dispersion 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 crew cut but this time the solid dispersed within the fluid is a magnetically soft material (such as iron) and the properties of the fluid are neutered by applying a magnetic field. In both cases the dispersed 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 relevant 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 clearly shows the effect of a magnet on such an MR fluid. With ER fluids a field dominance 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 abatement fluid Particle Figure 7 Schematic diagram demonstrate the structure of a electrorheological fluid between two electrodes. The top figure shows the structu re 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 identify uses were the automotive and aerospace industries where the fluids are used in vibration damping and variable torque transmission. MR dampers are used to control the fault in cars to allow the feel of the ride to be varied. Dampers are also used in prosthetic limbs to allow the patient to adapt to various movements for example the change from running 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 abstract stage are now moving forward. Look at the advances in information and comforts provided through smart materials and structures in automobiles. Automobiles can be taken to a garage for service and be hooked p to a diagnostic computer that tells the 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 nature of the problem and the severity of it? This approach mimics a cartoon that appeared several years past 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 chemic delivery to print organic light-emitting polymers in a fine power point on various media.Why not take the same application to compound smaller molecules? With the right set one could synthesize smaller molecules in significant amounts for characterization 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 literature. This is the group of smart mucilaginouss. We previously mentioned that PVDF film strips have been placed within an gummy joint to monitor performance. Khongtong and Ferguson developed a smart gummed at Lehigh University. 0 They suggested that this new adhesive could form an antifouling coating for sauceboat 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 appearing more frequen tly in the literature. A theme of research that was in the literature a few years ago was smart clothes or wearable computers being studied at MIT. The potential of this concept is enormous. This sounds wonderful as long as we make up ones mind how to work smarter, not longer.CONCLUSION From the abilities of the smart material to respond the environmental changes the termination arises that smart in the name do not meet the definition of being smart, that is, responding to the environment in a reversible manner. Due to their properties they moldiness deserve a great future. REFERENCES 1Mechanical Engineers Handbook Materials and Mechanical Design, Volume 1, trey 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. html 6http//virtualskies. arc. nasa. gov/research/youdecide/Shapememalloys. html