60007
Effects of Permanent Loads on Mechanical Performance of Nitinol Tubes
Effects of Permanent Loads on Mechanical Performance of Nitinol Tubes
Wednesday, May 8, 2024
Meeting Room I (Hotel Cascais Miragem)
Nitinol is frequently used as raw material for cardiovascular endoprosthesis, due to their high biocompatibility and properties such as pseudoelasticity. Nitinol devices are crimped to small diameters to deliver to the anatomical location.
Thereby, the microstructural and mechanical changes generated by mechanical load conditions in Nitinol tubes are studied, to monitor the pseudoelastic properties as a function of load time.
Consequently, a permanent load test is carried out by means of a fixture with parallel clamps, in other to generate deformation of the cross-sectional area of the tube. The procedure consists of deforming 5 mm long samples for 7 mm outer diameter tubes with a wall thickness of 0.5 mm in straight annealed condition at room temperature.
For this test, tubes from two ingots with different transformation temperatures were compared. The test was carried out with strains of 2%, 4%, 6% and 8% to simulate different device crimp strains. Parts were analyzed after time intervals up to 6 months under load.
Afterwards the geometrical changes of the samples were measured. Additionally, the samples were and characterized by DSC and XRD measurements. Primary results indicated that both strain and time affect the pseudoelastic properties, that appear as geometrical changes. However, no quantitative differences in DSC and XRD measurements were observed.
Thereby, the microstructural and mechanical changes generated by mechanical load conditions in Nitinol tubes are studied, to monitor the pseudoelastic properties as a function of load time.
Consequently, a permanent load test is carried out by means of a fixture with parallel clamps, in other to generate deformation of the cross-sectional area of the tube. The procedure consists of deforming 5 mm long samples for 7 mm outer diameter tubes with a wall thickness of 0.5 mm in straight annealed condition at room temperature.
For this test, tubes from two ingots with different transformation temperatures were compared. The test was carried out with strains of 2%, 4%, 6% and 8% to simulate different device crimp strains. Parts were analyzed after time intervals up to 6 months under load.
Afterwards the geometrical changes of the samples were measured. Additionally, the samples were and characterized by DSC and XRD measurements. Primary results indicated that both strain and time affect the pseudoelastic properties, that appear as geometrical changes. However, no quantitative differences in DSC and XRD measurements were observed.