Parametric FEA Study Of The Impact Of The Diamond Shape Design On The Fatigue Performance Of Nitinol Vascular Implants

To investigate the fatigue performance of a Nitinol vascular implant a common approach is to use diamond shape samples with similar geometry and shape setting processes similar to the final device. In fatigue tests, the diamond shape samples are dynamically loaded with different mean and alternating strains until they break, to gain insights into the fatigue behavior of the device.

In this study a parametric FEA model of a generic Nitinol diamond shape sample was set up for a systematic evaluation of the fatigue behavior. A fatigue simulation of the diamond shape sample was performed with a typical displacement during a fatigue test. For the simulation the commercial code Abaqus was used and the following geometric parameters where automatically varied using a custom script:

• tip width
• kerf width
• strut length
• strut width
• wall thickness
• connection width

For every combination of the above mentioned parameters the fatigue life was evaluated. Goodman diagrams of alternating versus mean strain were plotted and compared to each other.

Following an analysis of the results, the influence of the different geometric parameters on the fatigue behavior of a generic Nitinol diamond shape is discussed and a classification for an optimal fatigue diamond is presented.