Stress monitoring in Nitinol by gradient echo magnetic resonance imaging
Van Faassen E, Bakker C, Peeters J
The functional properties of Nitinol implants, like self-expansion of stents and filters, are determined by microcrystalline transition, which depends on the thermal-mechanical behavior of the material. As magnetic properties change at crystal structure transitions, magnetization measurements may be used to characterize the thermal-mechanical state. Therefore, a study was performed to investigate the potential of MRI to monitor stress-induced crystal structure transitions. Magnetization changes during elongation of a Nitinol wire were quantified by gradient echo susceptibility artifact analysis and related to measurements with a tensile tester. Results indicate that magnetization measurements can provide direct feedback of stresses in the specimen.