The thermal effect of memory is a specific effect of the so-called smart materials as artificial muscles and other materials , producing a reaction to a stimulus.
way memory effect was first observed by Chand and Read in 1951 in a gold-cadmium alloy, and in 1963, Buehler et al. described this effect in nitinol, an alloy of nickel-titanium equiatómica.
This effect metals and ceramics is based on a change in the crystalline structure called martensite phase transition. The disadvantage of these materials is that it is a mixture equitaómica and deviations of 1% change in the composition of the transition temperature at about 100 K.
Some metals and ceramics have the effect bidirectionally, which means that at a certain temperature has a form and it can be changed by changing the temperature, but if the first temperature is recovered, also the first form is recovered. This is accomplished by training the material for each shape at each temperature.
metals and ceramics thermally induced two-way effect memory have been widely used in medical implants, sensors, transducers, etc. Many have, however, a risk due to its high toxicity.
The shape memory alloys (SMA) have gained considerable commercial interest in recent years due to the wide range of functions that can perform in the field of medicine, dentistry and electronics applications. Within the group of alloys which has the shape memory phenomenon highlights which are alloys of nickel and titanium. The shape memory effect and super elasticity of the nickel-titanium alloy was discovered by Buehler et al in 1963 The most famous of these alloys was designed and released by the laboratories of the U.S. Navy in the 70's and is named in reference to the laboratories of that institution: Nitinol (Nickel Titanium Naval Ordnance Laboratories). Worldwide, there are many companies engaged in the production of the alloy. However, companies that manufacture products with high added value engineering are very few. As an example we can cite the Nitinol tube production is reduced to five companies worldwide. [2] The complexity for the working and complications at the time of production make products require many hours of engineering design process, and often times longer tuning. While the SMA are studied by science in its capacity as basic and applied science, relevant publications tend to show a little too basic physical, or sometimes, when referring to industrial data, are petty and inaccurate. The first pieces of Nitinol were manufactured in 1991 by Raychep corp. a set of steerable periscopic devices. Today in the market are stents1 with superelastic behaviors that replace the functions of the existing stents. Some other applications that are made of Nitinol can be catheters, orthodontic components in general, and other devices that can be named. Maria Linares
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