Z. C. Lin, K. Pike, Abbott Vascular Inc., Santa Clara, CA; A. Zipse, M. Schlun, Bard Peripheral Vascular, Karlsruhe, Germany
Nitinol fatigue life versus both alternating strain (range 0.25% -1.50%) and mean strain (range 1.0% -4.0%) was investigated. The testing specimens were made of medical grade nitinol tube and experienced a stent processing, which includes 1) laser-cutting, 2) heat-expansion and 3) electropolishing. The sub-size and dog bone-like specimens for the fatigue test have stent-like surface finish.
Tension-tension fatigue test were conducted in 37 C water - a simulated physiological environment. In this strain-controlled fatigue test, the oscillating stress of the testing specimens was monitored during the fatigue period to ensure the tests in a valid tension-tension mode. Failure analysis for the fracture specimens is provided for determination of the root cause of the fatigue failure. This study was conducted in the course of the work of a consortium of several stent manufacturers, SAFE Technology Limited and Dassault Systèmes Simulia Corp., dedicated to the development of fatigue laws suitable for life prediction of Nitinol devices.
This paper is to report Nitinol fatigue life as a function of alternating and mean strains. The fatigue tests were conducted using sub-size dog-bone specimens that have stent-like process. The purpose is to obtain a result that can be applied for design of medical devices – such as a stent.
This study was conducted in the course of the work of a consortium of several stent manufacturers, SAFE Technology Limited and Dassault Systèmes Simulia Corp., dedicated to the development of fatigue laws suitable for life prediction of Nitinol devices.
