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1. shape memory alloys

1.1.what is shape memory alloys?
shape memory alloys (SMA's) are metals , which have two many unique properties , pseudo-elasticity and shape memory effect , Arne Olander observed these unusual properties , and there were no any serious researches before 1960 in this field .
The most effective and widely used alloys include NiTi (Nickel - Titanium), CuZnAl, and CuAlNi.



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1.2. how shape memory alloys work:-


The two unique properties described above are made possible through a solid state phase change, that is a molecular rearrangement, which occurs in the shape memory alloy. Typically when one thinks of a phase change a solid to liquid or liquid to gas change is the first idea that comes to mind. A solid state phase change is similar in that a molecular rearrangement is occurring, but the molecules remain closely packed so that the substance remains a solid. In most shape memory alloys, a temperature change of only about 10C is necessary to initiate this phase change. The two phases, which occur in shape memory alloys, are Martensite, and Austenite.
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1.3. what is Martensite and Austenite??

Martensite, is the relatively soft and easily deformed phase of shape memory alloys, which exists at lower temperatures. The molecular structure in this phase is twinned which is the configuration shown in the middle of Figure 1. Upon deformation this phase takes on the second form shown in Figure 1, on the right. Austenite, the stronger phase of shape memory alloys, occurs at higher temperatures. The shape of the Austenite structure is cubic, the structure shown on the left side of Figure 1.

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1.4.Applications:
There are a lot of applications of shape memory alloys , in all fields:
Aircraft , Piping , Automotive , Telecommunication , medicine... etc.







2.Piezo Electric Material

2.1. What is piezo electric materials ?

The piezoelectric effect is the relation between a mechanical stress and an electrical voltage in solids , and it is the link between electrostatics and mechanics.
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The piezoelectric effect occurs only in non conductive materials. Piezoelectric materials can be divided in 2 main groups: crystals and cermaics. The most well-known piezoelectric material is quartz (SiO2).




2.2.piezoelectric materials
Here is a list of other piezoelectric materials:
  • Lithium tantalate
  • Polyvinylidene fluoride
  • Lanthanum gallium silicate
  • Potassium sodium tartrate





2.3. Applications:-
The most known application in Piezoelectric alloys is Sensors .
Piezoelectric sensor are devices using the piezoelectric effect to measure acceleration, pressure, strain or force and converting them to an electrical signal.











3.Magnetorheological Fluid:-

1.1 What are Magnetorheological Fluids:-
MR fluids are oils that are filled with iron particles. Often, surfactants surround the particles to protect them and help keep them suspended within the fluid. Typically, the iron particles comprise between 20 and 40 percent of the fluid's volume.


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1.2.What's the reason of Magnetorheological name ?

The term "magnetorheological" comes from this effect. Rheology is a branch of mechanics that focuses on the relationship between force and the way a material changes shape. The force of magnetism can change both the shape and the viscosity of MR fluids.


This video describes
A demonstration of a ferrofluid reacting to a magnet. The black liquid contains water and tiny iron particles that react to the magnet, locking together and dragging the water along with them. The spikes form along the invisible lines of magnetic force.







1.3.some applications of MR Fluids :-

Mechanical engineering , Military and defense , Optics , Automotive and aerospace... etc.











4.Auxetic Materials:-
What is Auxetic Materials?
An auxetic material is one which has a negative Poisson’s ratio, n1. This means that, unlike an elastic band for example, which gets thinner when stretched, an auxetic material will get fatter.look at this photo.


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Equally, if an auxetic material is compressed, it will get thinner. This interesting property is found in some natural materials such as single-crystal arsenic, catskin and load-bearing cancellous bone from human shins4. However, interest in this area really began to grow in 1987 when Roderic Lakes produced an auxetic polymeric foam at Iowa University. He achieved this by converting an ordinary foam using a relatively simple process of heating and squashing6. Since then, a whole range of synthetic auxetic materials have been produced, including carbon fibre composites7, honeycomb structures and microporous polymers9-11.
  1. ^ http://en.wikipedia.org/wiki/Shape-memory_alloy
    http://www.stanford.edu/~richlin1/sma/sma.html
    www.nnin.org/doc/NNIN-1030.pdf
    http://webdocs.cs.ualberta.ca/~database/MEMS/sma_mems/sma.html
    http://www.piezomaterials.com/Sensors.htm
    http://science.howstuffworks.com/liquid-body-armor2.htm