The team was unfamiliar with the characteristics of Nitinol prior to beginning the project, so initial testing was conducted to learn more information on Nitinol and its shape memory behaviors. The following is an overview of the testing procedure and a summary of the results. It should be noted that while this testing was an attempt to quantify the force Nitinol is capable of producing, the quantified results are unreliable. Instead, the team used the trends of the results, paired with prototype testing, to make design decisions
The following procedure is adapted from a high school material science activity guide.
Testing Procedure:
- We are going to calculate the force of the memory wire. Place a piece of Nitinol on a tall flat surface, like a table, with 9 inches of wire hanging over the edge of the surface.
- Take your piece of Nitinol wire and a mass set. Then you will bend your Nitinol wire to a right angle with the edge of the table.
- You will hold one end of the Nitinol wire against the table, possibly with tape. Make sure you have a good grip because it may move. The other end of the wire should be bent into a hook shape.
- You want a small hook at the end of the wire, as achieved when you take a pencil and wrap the last centimeter of the wire over the pencil.
- Starting with the smallest mass (8.5 g), you will then hook your mass to the wire (you may use an additional centimeter of tape to tape the mass and the wire together). The mass should be hanging at the end of the wire.
- Take your hairdryer and set it to high heat. Direct the hairdryer so the heat hits the part of the wire bent at the edge of the table. Hold the hairdryer in a way so it is directed down (be sure to not be directing the heat at yourself or others). Heat the wire for no more than 25 seconds.
- Observe whether the wire is able to lift the mass and record data in the data table.
This testing procedure was followed using 1 mm wire with a transition temperature of 15C, 45C, and 80C. The results showed a trend that the higher transition temperatures were capable of lifting higher masses. However, Dr. Deng could not confirm that this trend would appear in our later experimentation.
The testing procedure was also used to examine 2 mm wire with a transition temperature of 60C. This wire proved to lift higher masses and these results were confirmed by Dr. Deng.