| Title | Experimental Evaluation of Nitinol for Energy Dissipating Devices. |
| Authors | Sasaki, Kent K. |
| Publication | Department of Civil Engineering, University of California, Berkeley, Report No. UCB/SEMM-89/20, December 1989. |
| Objectives | Perform material tests on Nitinol to determine if it could be used as an energy dissipating device that would not develop permanent set. |
| Abstract | This report presents the results of experimental testing of the nickel-titanium alloy (Nitinol) for use in energy dissipating devices. Nitinol possesses the unique property of superelasticity - the ability of a material to be deformed past the proportional limit and up to a limiting strain and not incur permanent set. Though there is no permanent set, hysteresis and therefore energy dissipation does occur. The overall purpose of this report was to determine if Nitinol could be used as an energy dissipating device which would not develop permanent set. The following material tests were conducted to gain an understanding of Nitinol deformation behavior: (1) torsion tests on rectangular Nitinol bars (2) bending tests on rectangular Nitinol bars (3) bending tests on X-shaped Nitinol bars (4) tensile tests on Nitinol wire (5) tensile tests on Nitinol springs (6) earthquake simulation testing of a model 3-story structure base isolated with Nitinol springs. The results of the material tests revealed that for Nitinol to be used effectively as an energy dissipating material without incuring permanent set the deformation type and device shape should be such that uniform strains are developed over the cross-section and length of the Nitinol device. For the torsion and bending tests, non-uniform strains were developed and significant amounts energy dissipation were accompanied by permanent set. Efficient devices which could produce uniform strains are uniaxial tension members or thin-walled circular tubes loaded in pure torsion. |
