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    STP1616

    Effect of Variable Amplitude Loading in Nitinol Fatigue

    Published: 2019


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    Abstract

    In this investigation, diamond-shaped samples laser-cut from nitinol tubing were used to investigate the effect of variable amplitude fatigue loading. Alternating strain amplitudes of 0.30 %, 0.35 %, and 0.40 % were applied with periodic high strain amplitude of 0.70 %. The high strain was applied one time for every 40 low strain cycles. Using the obtained data, the appropriateness of the Palmgren-Miner’s linear and the Marco-Starkey nonlinear cumulative damage models was investigated. The variable amplitude testing results indicated a trend of decreasing fatigue life with the addition of periodic high strain. Data obtained were not sufficient to demonstrate that the Palmgren-Miners model was an accurate predictor. However, the Markco-Starkey model was found to provide additional flexibility in obtaining more precise predictions. With fatigue-to-fracture data and an appropriate variable amplitude model, the life associated with the variable amplitude loading can be estimated, and burdensome and lengthy physical variable amplitude testing can be avoided.

    Keywords:

    nitinol, fatigue, variable, amplitude, cyclic, strain, fatigue-to-fracture


    Author Information:

    Choules, Brian D.
    Dept. of Mechanical Engineering, Embry-Riddle Aeronautical University, Prescott, AZ

    Lewis, Alexandra L.
    Medical Device Engineering, MED Institute, West Lafayette, IN

    Gulker, Brandon G.
    Medical Device Engineering, MED Institute, West Lafayette, IN

    Metcalf, Justin M.
    Medical Device Engineering, MED Institute, West Lafayette, IN

    Kelley, Jace D.
    Medical Device Engineering, MED Institute, West Lafayette, IN


    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP161620180035