The Effects of Dietary Acids on Nitinol Wire

This experiment was conducted with the intention of determining how the tensile strength of the metal nitinol was affected by varying concentrations of citric and phosphoric acid. The purpose of this was to determine how the strength of the nitinol wire used in braces would be affected by acids commonly found in food and whether it posed a danger to the function of the braces. The expected outcome of the experiment was predicted to be that the treatments would weaken the wires, with the highest molarity of phosphoric acid (0.912 M) being most effective. Forty two wires, each 6 inches long, were randomly selected to be place in one of each of the solutions for 96 hours. After acid exposure, the tensile tests were performed on the wires by a 33R 4201 Instron. After the data was collected, a series of statistical tests were run. Two ANOVA tests were conducted to determine the statistical significance of the data in general, and a series of two sample T-tests were run to determine significance of data sets when an obvious significant effect was not implied in a box plot. The ANOVA returned a P-Value of 0.0354 when the results of wires exposed to citric compared to the standard and 0.0161 for phosphoric trial compared to the standards, rejecting the null hypothesis at an alpha level of 0.1 for each set.  This meant that there was a statistically significant effect in the tensile strength of the metal after treatment with acid. The hypothesis that the metals would be weakened and that the phosphoric acid would have the greatest change was rejected. All metals showed a positive change in strength, meaning that their tensile strengths were higher than the control group’s tensile strength after acid exposure. Further research into the metal’s ductility is required to determine the cause of this change.

Research Conducted By:

Kelly Rayner
Lake Shore High School

Lindsey Rejc
Cousino High School