smart+materials-seminar+1

** Cairo University, ** ** Faculty of Engineering, ** ** Credit Hours System, ** ** Mechanical Design Engineering **. Seminar I     --- Presented By: Mostafa Mohy Hassan Ali………………1092179 Ismail Mahmoud El- Nahas……………..1082631 Omar Mohsen Abd El-Azim…………….1092369 Mahmoud Essam El-Din…………………1071051 Hesham Mohsen…………………………1093233 Work distribution: Mostafa Mohy part-1 Shape Memory Alloy Ismail Mahmoud part-2 Magnetorheological fluid Omar Mohsen Part-3 Mahmoud Essam part-4 Hesham Mohsen part-5 Auxetic Materials

 ** Part-1 ** ** Shape memory alloy ** ** Introduction: ** A shape-memory alloy (SMA, smart metal, memory metal, memory alloy, muscle wire, smart alloy) is an [|alloy] that "remembers" its original, cold-forged [|shape] : returning the pre-deformed shape by heating. This material is a lightweight, solid-state alternative to conventional actuators such as hydraulic, pneumatic, and motor-based systems. Shape-memory alloys have applications in industries including medical and aerospace. The three main types of shape-memory alloys are the copper-zinc-aluminum-nickel, copper-aluminum-nickel, and nickel-titanium (NiTi) alloys but SMAs can also be created by alloying zinc, copper, gold and iron. . ** History: ** The first reported steps towards the discovery of the shape-memory effect were taken in the 1930s. According to Otsuka and Wayman, A. Ölander discovered the pseudo elastic behavior of the Au-Cd alloy in 1932. Greninger and Mooradian (1938) observed the formation and disappearance of a martensitic phase by decreasing and increasing the temperature of a Cu-Zn alloy. The basic phenomenon of the memory effect governed by the thermo elastic behavior of the martensite phase was widely reported a decade later by Kurdjumov and Khandros (1949) and also by Chang and Read (1951). ** Applications: ** 1- Variable Geometry Chevron using shape-memory alloy that reduces aircraft's engine noise .   2- Piping 3- Robotics

4- Eyeglass frames 5- Shape Memory Alloy heat engines ** Videos showing shape memory alloys application ** [] [] [] ** External materials: ** [] [] [] ** References: ** [] http://smartstructures.wikispaces.com/report1-samehalsayed [] []  Part-2 Magnetorheological fluid MR are oils thar are filled with iron particles. Also surfactants surround the particles to protect them and help keep them suspended within the fluid. The iron particles is about 20 and 40 percent f the fluid’s volume. The particles are tiny, measuring between 3 and 10 microns. However, they have a powerfull effect on the fluid’s consistency. When exposed to magnetic field, the particles line up, thickening the fluid dramatically. The hardening process takes around twenty thousandths of a second. The effect can vary dramatically depending on the composition of the fluid and the size, shape and strength of the magnetic field. <span style="font-family: Arial,sans-serif; font-size: 16pt;">Modes of operation and applications <span style="font-family: Arial,sans-serif; font-size: 10pt;">An MR fluid is used in one of three main modes of operation, these being flow mode, shear mode and squeeze-flow mode. These modes involve, respectively, fluid flowing as a result of pressure gradient between two stationary plates; fluid between two plates moving relative to one another; and fluid between two plates moving in the direction perpendicular to their planes. In all cases the magnetic field is perpendicular to the planes of the plates, so as to restrict fluid in the direction parallel to the plates.

<span style="font-family: Arial,sans-serif; font-size: 10pt;">] **<span style="font-family: Arial,sans-serif; font-size: 13pt;">Flow mode ** <span style="color: #0b0080; font-family: Arial,sans-serif; font-size: 10pt; text-decoration: none;">

<span style="color: #0b0080; font-family: Arial,sans-serif; font-size: 10pt; text-decoration: none;">
 * <span style="font-family: Arial,sans-serif; font-size: 13pt;">Shear mode **

<span style="font-family: Arial,sans-serif; font-size: 10pt;">] **<span style="font-family: Arial,sans-serif; font-size: 13pt;">Squeeze-flow mode ** <span style="color: #0b0080; font-family: Arial,sans-serif; font-size: 10pt; text-decoration: none;"> <span style="font-family: Arial,sans-serif; font-size: 10pt;">The applications of these various modes are numerous. Flow mode can be used in dampers and shock absorbers, by using the movement to be controlled to force the fluid through channels, across which a magnetic field is applied. Shear mode is particularly useful in clutches and brakes - in places where rotational motion must be controlled. Squeeze-flow mode, on the other hand, is most suitable for applications controlling small, millimeter-order movements but involving large forces. This particular flow mode has seen the least investigation so far. Overall, between these three modes of operation, MR fluids can be applied successfully to a wide range of applications. However, some limitations exist which are necessary to mention here.

<span style="font-family: Arial,sans-serif; font-size: 16pt;">Limitations <span style="font-family: Arial,sans-serif; font-size: 10pt;">Although smart fluids are rightly seen as having many potential applications, they are limited in commercial feasibility for the following reasons: <span style="font-family: Arial,sans-serif; font-size: 10pt;">Commercial applications do exist, as mentioned, but will continue to be few until these problems (particularly cost) are overcome.
 * § <span style="font-family: Arial,sans-serif; font-size: 10pt;">High density, due to presence of iron, makes them heavy. However, operating volumes are small, so while this is a problem, it is not insurmountable.
 * § <span style="font-family: Arial,sans-serif; font-size: 10pt;">High-quality fluids are expensive.
 * § <span style="font-family: Arial,sans-serif; font-size: 10pt;">Fluids are subject to thickening after prolonged use and need replacing.
 * § <span style="font-family: Arial,sans-serif; font-size: 10pt;">Settling of ferro-particles can be a problem for some applications.

<span style="font-family: Arial,sans-serif; font-size: 10pt;">This a video which shows how the MR act when exposed to a magnetic field []



References [] []

<span style="font-family: 'Times New Roman',serif; font-size: 12pt;">The piezoelectric effect describes the relation between a mechanical stress and an electrical voltage in solids. It is reversible: an applied mechanical stress will generate a voltage and an applied voltage will change the shape of the solid by a small amount (up to a 4% change in volume). **History** The piezoelectric effect was discovered in 1880 by the Jacques and Pierre Curie brothers. They found out that when a mechanical stress was applied on crystals such as tourmaline, topaz, quartz, Rochelle salt and cane sugar, electrical charges appeared, and this voltage was proportional to the stress. Piezoelectric materials produce a voltage in response to an applied force, usually a uniaxial compressive force. Similarly, a change in dimensions can be induced by the application of a voltage to a piezoelectric material. In this way they are very similar to electro-strictive materials. These materials are usually ceramics with a perovskite structure. The perovskite structure exists in two crystallographic forms. Below the Curie temperature they have a tetragonal structure and above the Curie temperature they transform into a cubic structure. In the tetragonal state, each unit cell has an electric dipole, i.e. there is a small charge differential between each end of the unit cell. A mechanical deformation (such as a compressive force) can decrease the separation between the cations and anions which produces an internal field or voltage. <span style="font-family: 'Times New Roman',serif; font-size: 12pt;">Video 1 : <span style="font-family: 'Times New Roman',serif; font-size: 12pt;">[] <span style="font-family: 'Times New Roman',serif; font-size: 12pt;">Video 2 : __<span style="font-family: 'Times New Roman',serif; font-size: 12pt;">http://www.youtube.com/watch?v=tjntpHM0RLw&feature=related __
 * <span style="font-family: 'Times New Roman',serif; font-size: 24pt;">Part-3 **
 * <span style="font-family: 'Times New Roman',serif; font-size: 24pt;">Piezoelectric materials **
 * <span style="font-family: 'Times New Roman',serif; font-size: 18pt;">Introduction: The piezoelectric effect **
 * <span style="font-family: 'Times New Roman',serif; font-size: 18pt;">Materials **

The piezoelectric effect occurs only in non conductive materials. Piezoelectric materials can be divided in 3 main groups: crystals, ceramics, polymers [|Quartz (//SiO2//])
 * Crystals: **

[|Berlinite (//AlPO4//])

[|Gallium orthophosphate (//GaPO4//])

[|Tourmaline]
 * Ceramics: **

[|Barium titanate (//BaTiO3//])

[|Lead zirconate titanate(//PZT//]) Potassium niobate (KNbO3) [|Lithium niobate] (LiNbO3) <span style="color: windowtext; font-family: 'Times New Roman',serif; font-size: 12pt; text-decoration: none;">[|Lithium tantalate] <span style="font-family: 'Times New Roman',serif; font-size: 12pt;"> (LiTaO3) <span style="color: windowtext; font-family: 'Times New Roman',serif; font-size: 12pt; text-decoration: none;">[|Sodium tungstate] <span style="font-family: 'Times New Roman',serif; font-size: 12pt;"> (Na2WO3) <span style="color: windowtext; font-family: 'Times New Roman',serif; font-size: 12pt; text-decoration: none;">[|Zinc oxide] <span style="font-family: 'Times New Roman',serif; font-size: 12pt;"> (Zn2O3)


 * <span style="font-family: 'Times New Roman',serif; font-size: 13.5pt;">Polymers **
 * <span style="color: windowtext; font-family: 'Times New Roman',serif; font-size: 12pt; text-decoration: none;">[|Polyvinylidene fluoride] <span style="font-family: 'Times New Roman',serif; font-size: 12pt;"> (PVDF): PVDF exhibits piezoelectricity several times greater than quartz. Unlike ceramics, where the crystal structure of the material creates the piezoelectric effect, in polymers the intertwined long-chain molecules attract and repel each other when an electric field is applied.

Currently, industrial and manufacturing is the largest application market for piezoelectric devices, followed by the automotive industry. Strong demand also comes from medical instruments as well as information and telecommunications. The global demand for piezoelectric devices was valued at approximately US$14.8 billion in 2010. The largest material group for piezoelectric devices is piezocrystal, and piezopolymer is experiencing the fastest growth due to its light weight and small size.
 * Applications **
 * Piezoelectric crystals are now used in numerous ways: **

[|**http://www.whystudymaterials.ac.uk/students/fun/piezo.asp**] [|**http://www.piezomaterials.com/index.htm**]
 * Links &references **
 * For more information about piezoelectric materials **
 * __http://en.wikipedia.org/wiki/Piezoelectricity__**


 * __<span style="font-family: 'Times New Roman',serif; font-size: 16pt;">Part-4 __**


 * __<span style="font-family: 'Times New Roman',serif; font-size: 16pt;">Introduction: __**

<span style="font-family: 'Times New Roman',serif; font-size: 12pt;">Ionic polymer–metal composites (IPMCs) form an important category of electro active polymers which have both built-in actuation and sensing capabilities. Due to their large bending displacement, low driving voltage, resilience, and biocompatibility, IPMCs have been explored for potential applications in bio mimetic robotics, medical devices, and micromanipulators. In most of these applications, compact sensing schemes are desired for feedback control of IPMC actuators to ensure precise and safe operation without using bulky, separate sensors. It is intriguing to utilize the inherent sensory property of an IPMC to achieve simultaneous actuation and sensing, like the self-sensing scheme for piezoelectric materials, However, this approach is difficult to implement due to the very small magnitude of the sensing signal compared to the actuation signal (milli volts versus volts) and the nonlinear, dynamic sensing responses. Newbury explored the idea of using two 3 Author to whom any correspondence should be addressed. IPMCs, mechanically coupled in a side-by-side configuration, to perform actuation and sensing. The attempt was reported to be unsuccessful since the sensing signal was buried in the feed through signal from actuation.




 * __<span style="font-family: 'Times New Roman',serif; font-size: 16pt;">History: __**

In the mid-1990s, Qiming Zhangand co-workers at Pennsylvania State University in University Park demonstrated strains in their ferroelectric polymers of 4 percent--not a lot, but it comes with a lot of force: about a gigapascal. But Zhang's technology is not quite ideal, in part because it needs high voltages to deliver musclelike power and energy.

In the graft elastomer, a long backbone molecule is engrafted with elements that respond to an electric field. A rather high voltage contracts the entire structure. One such material, developed by Ji Su at NASA Langley, in Hampton, Va., produced a strain of about 4 percent and a rather strong force.

Liquid-crystal muscles work by undergoing a sudden phase change from an ordered crystalline phase to a disordered soup when electrically heated through the phase transition temperature. Groups, particularly teams in the U.S. Navy and in Germany, have been reporting great forces, as well as greater stretch than that found, say, in ferroelectrics. But the need to heat and cool the muscles makes them slow to respond and inefficient.

Electrostrictive paper is a type of artificial muscle discovered serendipitously by Jaehwan Kim at Inha University, in Inchon, South Korea, who began his experiments, essentially, with cellophane tape. Glue two layers of silvered tape together and, surprisingly, the end product will shrink when charged. After varying the numbers of layers and the materials in the electrodes and adhesives, he found a reasonable, and very cheap, technology for large-area applications. One idea people have for using electrostrictive paper is to make an electronically active form of acoustic tile. The tile would broadcast antinoise to cancel out sound in a room.


 * __<span style="font-family: 'Times New Roman',serif; font-size: 16pt;">Characteristics: __**

Just as various assortments of ionic muscles exists. In general, the Ionics are less energy efficient--less than 30 percent, even under the best conditions, compared with the 80 percent seen in some of the electronic muscles. But they have the advantage in at least two respects: they react to drive voltages as low as 1-5 volts, compared with the electronics' tens of volts per micrometer of thickness. Even better, they readily produce bending motions, rather than just expanding or contracting.

Polymer gels--materials formed of chainlike molecules dissolved in a solvent to form a semisolid--have been investigated for years as sensing devices as well as actuators. Chemical stimulation is possible--changing the acidity of the surrounding liquid can, for instance, cause a movement of ions into or out of the gel, forcing it to contract or expand. But electrical stimulation can produce the same effect and is more convenient for most machine designs.


 * __<span style="font-family: 'Times New Roman',serif; font-size: 16pt;">Video: __**

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 * __<span style="font-family: 'Times New Roman',serif; font-size: 16pt;">Further readings: __**

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** Part-5 **

** Smart Structures And Their Applications **

** Auxetic Materials **

Auxetic materials are materials that have a negative Poisson's Ratio. They become thicker perpendicular to the applied force, when stretched.

Such behavior is in contrast to ordinary materials, which get thinner when stretched.

1- Variable Geometry Chevron using shape-memory alloy that reduces aircraft's engine noise Foams with negative Poisson's ratios were produced from conventional low density open-cell polymer foams by causing the ribs of each cell to permanently protrude inward, resulting in a re-entrant structure.

Auxetic materials are not natural; they are foams with specifically engineered microstructures.

Examples of auxetic materials include:


 * Certain rocks and minerals.
 * Living bone tissue (although this is only suspected)
 * Specific variants of [|polytetrafluorethylene] polymers such as Gore-Tex.
 * Paper, all types. If a paper is stretched in an in-plane direction it will expand in its thickness direction due to its network structure.

** A Brief History of the Material: **

Scientists have known about auxetic materials for over a 100 years. The earliest published example of a synthetic auxetic material was in //Science// in 1987, entitled "Foam structures with a Negative Poisson's Ratio" by R.S. Lakes from the University of Iowa. He produced auxetic polymeric foam by converting ordinary foam using a relatively simple process of heating and squashing. Since then, a whole range of synthetic auxetic materials have been produced, including carbon fibre composites, honeycomb structures and microporous polymers. The use of the word //auxetic// to refer to this property probably began in 1991.

** Current Industrial Applications: **

It is anticipated that re-entrant foams may be used in such applications as sponges, robust shock absorbing material, air filters, biomaterials and fasteners.

Auxetic foam and honeycomb filters offer enhanced potential for cleaning fouled filters, for tuning the filter effective pore size and shape, and for compensating for the effects of pressure build-up due to fouling.

Key areas of application are seen in the biomedical field. Prosthetic materials, surgical implants, suture/muscle/ligament anchors and a dilator to open up blood vessels during heart surgery are all possible. Another area relates to the use of auxetic materials in piezoelectric sensors and actuators.

Also the breakthrough development of a continuous process to produce auxetic materials in fibrous form has created the opportunity to apply their unique characteristics in a wide range of applications previously not possible. Fibres can be used in single or multiple filament structures and can be used to produce a woven structure.



** Links: **

Videos:

= The strange behaviour of auxetic foams =

= [] =

Further reading:

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http://www.azom.com/article.aspx?ArticleID=168

References:

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http://en.wikipedia.org/wiki/Auxetics