Volume 4, Issue 6 (June 2007)

    Characterizing Fatigue Response of Nickel-Titanium Alloys by Rotary Beam Testing

    (Received 5 October 2005; accepted 6 May 2007)

    Published Online: 2007

    CODEN: JAIOAD

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    Abstract

    Fatigue information has been reliable in predicting wire critical structural integrity. The aim of this study is to expound on the characterization technique of rotary beam fatigue testing (RBT). By alternating tension and compression stress states through RBT, it is possible to determine the life expectancy of Nitinol monofilament round wires. Fatigue testing has been employed to characterize the influence of subtle changes in inclusion content, chemistry variations of raw material, ingot transformation temperatures of Nitinol (NiTi), and surface finish conditions for implant grade wires. Currently, an ASTM standard does not exist that concentrates solely on fatigue testing shape memory alloys. By exploiting part geometry, this testing technique serves to compliment other characterization methods. Evaluation of fracture surfaces has proven useful in diagnosing the factors influencing failures. The utilization of fatigue data and fracture mechanics compliments tensile testing in providing information to the design engineer. Results from studying flexural endurance, statistical Weibull life assessment analysis, fracture analysis, and a determination of stress/strain levels at the site of failure have proven useful in determining desired material properties for next generation medical devices.


    Author Information:

    Patel, Mitesh M.
    Shape Memory Engineer, Fort Wayne Metals Research Products Corporation, Fort Wayne, IN


    Stock #: JAI100390

    ISSN: 1546-962X

    DOI: 10.1520/JAI100390

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    Author
    Title Characterizing Fatigue Response of Nickel-Titanium Alloys by Rotary Beam Testing
    Symposium Fatigue and Fracture of Medical Metallic Materials and Devices, 2005-11-11
    Committee E08