Helical SMA NiTi Spring

Description

Helical SMA NiTi Spring

Click on “ADITIONAL INFORMATION” to get more details, such as: file size, simulation time, use instructions and FEM data (nodes and elements number)

Helical SMA NiTi Spring

This example is similar to the classic NiTi spring. In this case, the diameter is not constant but variable. This produces a behavior slightly different from that of the constant diameter spring. The advantage of this model is that, once the initial form is recovered, it is developed on a plane, which can be beneficial for actuators that do not allow much space. Therefore, the stroke of the spring is much greater than in the classic one.

In this case, we also have one fixed end and the other one free. At the free end, a load of 5N is again applied to the longitudinal axis of the spring. This load causes the deformation of the model or the internal change of the crystalline structure from twinned martensite to detwinned martensite. In this way, the material is ready for the shape memory effect. This occurs when heat is applied (+ 70 ° C) and the spring fully recovers the original flat shape.

Characteristics of the model:

– 0,75mm wire diameter

– Transformation temperature Af=+70ºC

– Force applied = 5N

– 6 coils

This is a two steps simulation:

1st step: 5N force is applied on the free end while the other is a fixed support. The spring stretches to 87mm long.

2nd step: a thermal condition of +120ºC is applied and the spring recovers its original flat shape.

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