smart+materials(ahmed+yousry)

Smart materials Shape memory alloy Shape memory alloys is a materials change its deformed shape returning to its origin shape (austenite phase). this processes can be done by heating around 90 C, or passing an electric current. It can return its origin shape (austenite phase) after folding it in a ratio 8% of its origin tall in the room temperature. the origin shape made by folding and clamping a wire of material in high heat or passing current for some time to consider that this folded wire is its origin shape. || || But it can do that southlands of time effectively by stretching it 3% to 5% of its origin talls. There are many application. for example : 1)muscle wire 2)surgicaltool 3)aeronautical application  || ﻿  ||  || ||

Pizoelictric materials Pizoelictric materials characterize with its ability to generate a potential between its two faces after changing its shape with stress and vice verse. **How piezoelectricity works ?**
 * 1) Normally, the charges in a piezoelectric crystal are exactly balanced, even if they're not symmetrically arranged.
 * 2) The effects of the charges exactly cancel out, leaving no net charge on the crystal faces. (More specifically, the electric dipole moments�vector lines separating opposite charges�exactly cancel one another out.)
 * 3) If you squeeze the crystal (massively exaggerated in this picture!), you force the charges out of balance.
 * 4) Now the effects of the charges (their dipole moments) no longer cancel one another out and net positive and negative charges appear on opposite crystal faces. By squeezing the crystal, you've produced a voltage across its opposite faces�and that's piezoelectricity!

What is piezoelectricity used for? Ultrasound Microphone Quartz watch clock Mr fluid Mr fluid is a fluid which its viscocity depent on tensity of magnetic flux. Typical MR fluid consists of these three parts: How it wok ? If a magnitic flux is found, the partcles will contact and making chains of particles which restrict the movement of the fluid.
 * **Carbonyl Iron Particles** -- 20 to 40 percent of the fluid is made of these soft iron particles that are just 3 to 5 micrometers in diameter. A package of dry carbonyl iron particles looks like black flour because the particles are so fine.
 * **A Carrier Liquid** -- The iron particles are suspended in a liquid, usually hydrocarbon oil. Water is often used in demonstrating the fluid.
 * **Proprietary Additives** to avoid Limitations

Applications :  Mechanical engineering Military and defense Optics Auto motive and aerospace Human prosthesis Auxetic materials Auxetic materials are materials with a negative Poisson�s Ratio, i.e. become fatter when stretched and thinner when squashed.

Structures for molecular auxetics have been proposed, which are expected to be intrinsically superior to the microstructural auxetics so far developed.

advantages of auxetic materials Apart from the scientific value of having materials with a negative Poisson`s ration, auxetic materials show enhanced mechanical properties such as: which make them superior to classical materials for many practical applications.
 * increased shear stiffness
 * increased plane strain fracture toughness
 * increased indentation resistance

Refrances
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