Las Aleaciones con Memoria de Forma, aleaciones Nickel-Titanio, NiTi o simplemnte Nitinol, son una clase de metales capaces de recuperar su forma original después de soportar grandes deformaciones, mucho mayores que los materiales convencionales.
Inicialmente, la estructura cristalina de la aleación se dispone en configuración de zig-zag, formando gemelos a ambos lados de lineas de simetría. Esta es la Martensita parejada. Cuando la aleación entra en tensión, la malla cambia a Martensita desparejada. Esta fase es estable y el material está listo para el efecto de Memoria de Forma. Cuando se aplica calor, la aleación entra en una fase de mayor energía o Austenita. La malla cristalina cambia de nuevo a una disposición ortogonal, más fuerte. Tan pronto como el material se enfría, la estructura cristalina cambia a la configuración inicial en zig-zag, completando el ciclo.
NiTi Shape memory effect
Visita nuestra tienda. Vendemos este ejemplo, así como muchos más archivos SMA resueltos para Ansys Workbench 18.1 o superior. Asimismo, si tienes un proyecto particular, no dudes en contactarnos e intentaremos ayudarte.
Finalmente, también puedes visitar nuestro canal de YouTube. Allí encontrarás el resto de nuestros ejemplos de simulación. Actuadores, dispositivos médicos, etc. con la tecnología SMA puede ahorrar espacio, peso, energía y todo ello con una actuación silenciosa, rápida y efectiva.
Let’s take a look at this Shape Memory NiTi spring in action. First, let’s examine the Stress-Strain-Temperature graph. Initially the crystal structure is in a zig-zag arragement (twinned martensite). The material forms twins along symmetry lines. When the alloy deforms in cold state, a temporary deformation is set and the zig-zag setup is stretched to a diagonal arragement. This is the detwinned martensite. The twins transform into a new tilted structure.
As a result, the crsytal structure is ready for the shape memory effect. Applying heat, makes the detwinned martensite transforms again into a regular, straight and cubic form and therefore, the remembered shape is set back again. This is the austenite, which is the strongest arragement of the alloy. During this state, the material is stronger, has a higher elacticity modulus and deformations are recoverable up to 8%.
Finally, when the material gets cold again, it returns to the initial twinned martensite, finishing and completing the cycle.
We can check this on the next video. On screen, there are two glasses of water. Hot on the left and cold on the right. This spring is a Nickel, Titanium and Copper alloy. The percentage of Copper in the alloy is 5% and the rest is Nickel and Titanium. Wire diameter is 1mm and outer diameter is 10mm. It deforms in cold state and when inserted in hot water, it recovers its original shape. Cold water helps to speed up the cooling process of the Ni-Ti alloy.
Shape Memory Effect NiTiCu Spring
Check out our new shop where you can find solved Ansys files for your SMA simulations. We also provide special services and support. Please feel free to contact us for helping you on your personal project. You can also visit our YouTube Channel for more videos on Shape Memory Alloys.
Shape Memory Alloys, Nickel-Titanium alloys, NiTi or simply Nitinol, are a very special kind of metals able to recover its original shape after very large deformations, usually larger than conventional materials.
Initially, the alloy’s crystal structure arranges in zig-zag position, forming twins along symmetry lines. This is the twinned martensite. When the alloys stresses, this mesh deforms to a detwinned martensite. This phase is stable and the material is ready for the shape memory effect. Once heat is applied, the alloy gets in a higher energy level state or austenite. The mesh changes again to a stronger ortogonal arragement. As soon as the material gets cold again, the crystal structure shifts to the initial zig-zag shape, finishing the cycle.
NiTi Shape memory effect
On this video, you can see a SMA spring in action. The Nickel-Titanium element is holding the weight of a tool. When is cold, the springs stretches and the tool goes down due to the force of gravity. When is hot, the SMA is stronger than the weight of the tool, therefore it goes up. This is just a simple example of how Shape Memory Alloys can be used. The rest of potential applications are up to your imagination. In your particular project, you can design your own mechanism.
The heat source can be electricity (Joule effect), hot water or liquid, gas, etc. To return the mechanism to the initial position, you can use gravity, another spring, material stiffness, etc. You can also use the heat of the sun or the difference between day and night as a way to activate/deactivate your alloy/actuator.
The actuation is fast, reliable and silent. This is especially important in applications where you want to save weight or cannot make any sound.
Privacy & Cookies Policy
Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.
Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent prior to running these cookies on your website.