Dissemination of IT for the Promotion of Materials Science (DoITPoMS)

DoITPoMS Teaching & Learning Packages Superelasticity and Shape Memory Alloys Shape Memory Effect - The "Ferris Wheel" Experiment
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Shape Memory Effect - The "Ferris Wheel" Experiment

An illustration of a shape memory effect is provided by the “ferris wheel” set-up shown in the accompanying video and simulation. Ten “trained” nitinol springs comprise the periphery of the wheel, connecting ten thin steel spokes, via relatively massive brass weights attached at their ends.  The “trained“, shape of these springs, which is promoted by heating, is the contracted form.  As individual springs cool, on the other hand, the forces acting between them tend to stretch them out again.

If the springs on one side of the wheel are heated, for example with a simple fan or radiant heater, then they tend to contract  -  ie to adopt the trained shape, as explained on the previous page.  This bends the adjacent spokes, so as to move the brass weights towards the side where the heater is located.  This creates a net moment tending to rotate the wheel.  Exactly how the wheel rotates depends on the heating and cooling characteristics, and also on the transformation characteristics of the SME and on the dimensions (wire and spring diameters) of the springs.

Watch a video of the actual wheel and then see what happens to the individual springs when they are heated and cooled

Video of wheel rotating on heating

Heating

Close up video of wheel springs heating

Cooling

Close up video of wheel springs cooling