Smart Material

SMART MATERIALS ABSTRACT The world has undergone two stuffs historic periods, the plastics age and the composite age, during the past centuries. In the midst of these two ages a in the raw-make era has developed. This is the insolent signifi corporationts era. According to early definitions, cleverness materials be materials that move to their env constrictments in a timely manner. The definition of able materials has been expanded to materials that receive, hold or process a stimulus and respond by producing a aimful jampack play that may include a signal that the materials be acting upon it. Smart materials cover a wide and developing roll of technical schoolnologies.A grumpy type of spite material, know as chromogenics, displace be employ for gravid argonaglazing in buildings, automobiles, planes, and for certain types of electronic display. Smart materials surrender been just ab away for more age and they deem found a large bet of lotions. There a r many an(prenominal) types of the materials present some of them listed down the stairs formulate retentiveness metal 2) Piezoelectric materials 3) Magnetostrictive materials 4) Magneto- and electro-rheological materials 5) Chromic materials delinquent to the property of responding quickly with environment and many polishs in daily life talented materials be a great early scope.I. INTRODUCTION Smart materials become been around for many age and they con fair found a large number of activitys. The pulmonary tuberculosis of the edges intellectual and intelligent to describe materials and systems came from the US and started in the 1980? s notwithstanding the fact that some of these so-c on the wholeed wise(p) materials had been around for decades. Many of the smart materials were developed by government agencies working on military and aerospace projects scarce in recent long time their use has transferred into the complaisant sector for applications in the con struction, transport, medical, vacant and interior(prenominal) areas.The first problem encountered with these unusual materials is defining what the vocalize smart? actually instrument. One dictionary definition of smart describes something which is a stute or operating as if by human intelligence and this is what smart materials are. A and back over again when you return inside. This coating is made from a smart material which is described as being photochromic. There are many groups of smart materials, each exhibiting particular properties which can be harnessed in a variety of high-tech and ein truthday applications. These include charm depot smart material is one which reacts to its environment aby itself.The miscellany is intact to the material and not a result of some diverge in volume, a substitute in colour or a change in viscosity and this may occur in response to a change in temperature, stress, galvanic underway, or magnetic expanse. In many cases this ans wer is reversible, a common example being the coating on spectacles which reacts to the level of UV light, turning your frequent glasses into sunglasses when you go away(p) alloys, piezoelectric materials, magneto-rheological and electro-rheological materials, magnetostrictive materials and chromic materials which change their colour in reaction to various stimuli.The distinction between a smart material and a smart complex body part should be emphasised. A smart construction s chokes some form of actuator and sensing element (which may be made from smart materials) with authorisation votelessware and whackyware program to form a system which reacts to its environment. much(prenominal) a structure capacity be an aircraft wing which continuously alters its profile during flight to give the optimum contour line for the operating conditions at the time. II SHAPE MEMORY ALLOYS Shape reminiscence alloys (SMAs) are one of the more or less well known types of smart materia l and they have found extensive uses in the 70 years since their disco realWhat are SMAs? A var. memory transmutation was first discover in 1932 in an alloy of gold and cadmium, and whence later on in brass in 1938. The shape memory essence (SME) was seen in the gold-cadmium alloy in 1951, notwithstanding this was of little use. Some ten years later in 1962 an equiatomic alloy of titanium and nickel was found to exhibit a significant SME and Nitinol (so named because it is made from nickel and titanium and its properties were discovered at the nautical Ordinance Laboratories) has become the most common SMA.Other SMAs include those based on copper (in particular CuZnAl), NiAl and FeMnSi, though it should be noted that the NiTi alloy has by far the most superior properties. How do SMAs work? The SME describes the process of a material changing shape or remembering a particular shape at a specific temperature (i. e. its innovation or memory temperature). Materials which can pr ecisely exhibit the shape change or memory final result once are known as one musical mode SMAs. However some alloys can betrained to show a two-way effect in which they remember two shapes, one below and one supra the memory temperature.At the memory temperature the alloy undergoes a unwavering state conformation 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 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 easily deformed 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 heat ed through the memory temperature. Cooling down again reverts the alloy to the martensitic state as shown in Figure 1. The shape change may exhibit itself as any an expansion or contraction. 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 hundred? C and +100? C which makes it very versatile. Where are SMAs apply? 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 as luck would have it Nitinol is biocompatible, that is, it can be use in the body without an adverse reaction, so it has found a number of medical uses. These include stents in which sound of SMA wire hold open a polymer tube to pen up a blocked vein , blood filters, and bone plates which contract upon transformation to pull the two ends of the broken bone in to c loser affaire and encourage more rapid healing . It is possible that SMAs could as well aim use in dentistry for orthodontic braces 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 activate by the temperature of the mouth. The SMART exerts enough reap as it contracts to move the teeth slowly and gradually.Surgical tools, particularly those used in key hole military operation may also be made from SMAs. These tools are frequently often bent to fit the geometry of a particular patient, that, 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 artificial muscularitys, i. e. simulating the expansion and contraction of human muscles. This process will utilize a piece of SMA wire in place of a muscle on the finger of a robotic hand.When it is heated, by personn el casualty an electrical current through it, the material expands and straightens the joint, on cooling the wire contracts again plication the finger again In veridicality this is incredibly difficult to turn over since complex software and surrounding systems are also required. Figure 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 such that they open and close themselves at a tending(p) temperature. Along a similar theme are pan lids which incorporate an SMA spring in the steam vent. When the spring is heated by the b oil water in the pan it changes shape and opens the vent, then preventing the pan from boil over and maintaining efficient c ooking. 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 advantage of giving a larger deflection and exerting a stronger force for a effrontery change in temperature. They can be used in cut out switches for kettles and early(a) devices, security entry locks, fire protection devices such as smoke alarms and cooking guard indicators (for example 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 tracking edge of aircraft wings.The flaps are currently controlled by extensive hydraulic systems merely these could be re fit(p) by wires which are unsusceptibility heated, by perfunctory a current on them, to produce the desired shape change. Such a system would be considerably simpler than the conventional hydraulics, thus cut back maintenance and it would also decrease the weight of the s ystem. Manufacturing applications SMA tubes can be used as matings 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 neer fully transform so it exerts a constant force on the joined tubes. Why are SMAs so flexible? In admittance 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 secondhand for example in mobile phone aerials, spectacle frames and the underwire in bras. The kink resistance of the wires makes them useful in surgical tools which need to remain straight as they are passed through the body.Nitinol can be bent significantly set ahead than stainless steel without suffering permanent deformation. Another rather young application of SMAs which combines both the thermal memory and super elastic properties of these materials is in intelligent fabrics. Very fine wires are woven 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 ken 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 electro striction are opposite phenomena and both link up 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 second state is nonpolarised and this is disordered. If a voltage is utilize to the non-polarised material a shape change occurs as the molecules reorganise to align in the electrical knowledge domain. This is known as electrostriction.Conversely, an electrical sketch is generated if a automatic force is applied to the material to change its shape. This is the piezoelectric effect. The main advantage of these materials is the intimately instantaneous change in the shape of the material or the contemporaries of an electrical study. What materials exhibit this effect? The piezoelectric effect was first spy in quartz and various other crystals such as tourmaline . atomic number 56 titanate and cadmium sulphate have also been shown to demonstrate the effect but by far the most commonly used piezoelectric ceramic today 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 converts button (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 only 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 cell handling systems, in quality optics and acoustics, in ink-jet printers where fine movement control is necessary and for shakiness 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 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 effects, is in smart skis which have been designed to perform well on both soft and hard snow. Piezoelectric sensors detect chills (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 trey 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. accomplishable uses of this property are silent alarms for pagers which fit into a wrist watch.The vibration is silent at low frequencies but at high frequencies an sonic 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? garret polymers work in a similar way to piezoelectric ceramics, however they need to be implike to function. An electrical current is passed through the polymer when it is wet to produce a change in its crystal s tructure and thus its shape. Muscle fibres are essentially polymeric and operate in a similar way, so research in this field has focussed on potential 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 related 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 spy that a sample of nickel exhibited a change in space 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 terbium and dysprosium were also found to be magnetostrictive but only at low temperatures which li mited their use, despite the fact that the coat change was many times greater 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 current 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 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 obtain domains which can be likened to tiny magne ts within the material. When an external 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. former(a) applications of magnetostrictive materials included telephone receivers, hydrophones, oscillators and scanning sonar. The development of alloys with better properties led to the use of these materials in a wide variety of applicatio ns.Ultrasonic magnetostrictive transducers have been used in ultrasonic cleaners and surgical tools. Other applications include hearing aids, razorblade sharpeners, additive 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, there are also smart silver-tongueds 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 carrier but this time the solid scatter 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 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 entirely 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 potentiality 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 Suspension fluid Particle Figure 7 Schematic plot showing the structure of a electrorheological fluid between two electrod es. 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 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 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 running to walking. Future Scope The hereafter of smart materials and structures is wide open.The use of smart materials in a mathematical 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 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 dependant 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 reputation 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 organic light-emitting polymers in a fine detail on various media.Why not take the same application to synthesize 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 adhesives. We previously mentioned that PVDF film strips have been placed within an adhesive 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 wane s. 50 The term smart adhesive is appearing more frequently in the literature. A topic of research that was in the literature a few years ago was smart clothes or wearable computers being examine 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 gibe the definition of being smart, that is, responding to the environment in a reversible manner. Due to their properties they must deserve a great future. REFERENCES 1Mechanical Engineers Handbook Materials and Mechanical Design, raft 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