SYMPOSIA PAPER Published: 19 July 2019
STP161620180034

A Statistically Rigorous Fatigue Strength Analysis Approach Applied to Medical Devices

Source

Statistical fatigue models are often constructed in one of two ways: (1) life construction, where fatigue life is a function of fatigue amplitude, or (2) strength construction, where fatigue strength is a function of life. Life construction is most common. Strength construction is slightly more complex to implement rigorously but gives a direct measure of the fatigue strength variability and has known benefits for goodness of fit. For general strength constructions with constant variability in fatigue strength, we derive a normalized distribution, which can be fit to any fatigue data set. The resulting construction is applicable to many fatigue ε-N functions that can be written in terms of strength, such as the Coffin-Manson equation. Maximum likelihood techniques are used to apply the construction to the fatigue of high-performance materials, such as superelastic nitinol, throughout the range considered in the design of implantable cardiovascular medical devices. The performance is compared to existing constructions and shown to have quantitative advantages in terms of goodness of fit. This approach is a statistically rigorous strength construction. The method can provide a valuable tool for medical device design.

Author Information

Falk, Wayne, M.
Medtronic Inc., Mounds View, MN, US
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Details
Developed by Committee: E08
Pages: 98–111
DOI: 10.1520/STP161620180034
ISBN-EB: 978-0-8031-7678-2
ISBN-13: 978-0-8031-7677-5