Table 1.
ASME VV-40 standard process flow.
Table 2.
Definition of the COUs and the related verification and validation activities addressed within this study.
Fig 1.
Stent model: (a) 2D sketch of the stent with detail of the functional unit used in the verification step; (b) comparison of crimped and expanded configurations; (c) functional unit; (d) superelastic Ni-Ti constitutive law; (e) details of width (ws) and thickness (ts) strut dimensions.
Fig 2.
Description of the steps for the simulations.
Step 1 includes the crimping of the sub-unit, which is either allowed a free release (COU-1) or deployed in contact with the vessel (COU-2) in Step 2. Finally, the deployed configuration is used to apply pulsatile blood conditions in Step 3 for fatigue analysis (COU-3).
Fig 3.
Mesh density: (a) uniform mesh of the functional stent unit; (b) details of the portion selected for the local QoI; (c) comparison of four different element densities.
Table 3.
Characteristics of mesh grids.
Table 4.
Characteristics of element integration.
Table 5.
Summary of the parameters for the calculation verification study.
Table 6.
Nickel-titanium material parameters used as reference in the sensitivity analysis.
Fig 4.
Calibration of materials used for the mock vessels: (a) experimental and computational stress-strain curves derived from the hoop tests on silicone material; (b) experimental and computational stress-strain curves derived from uniaxial tensile dog-bone specimens of Elastic 50A Resin.
Fig 5.
(a) Comparison of patient-specific geometries as 3D-printed resin vessels (top) and FE model (bottom); (b) sequence of stent deployment into a resin mock vessel; (c) DICOM cross-sectional image (left) and schematics of the performance indicators.
Fig 6.
Calculation verification on mesh density for radial compression simulation: (a) radial force–diameter curves; (b) maximum principal stress–time curves; (c) contour plots of maximum principal stress for different mesh grids.
Table 7.
Results of the calculation verification on mesh density applied to radial compression simulation.
Fig 7.
Calculation verification on element integration applied to crimping simulation using a mesh density 4 × 4: (a) radial force–diameter curves; (b) maximum principal stress–time curves; (c) contour plots of maximum principal stress.
Table 8.
Results of the calculation verification on element integration applied to radial compression simulation.
Fig 8.
Calculation verification on target time increment applied to crimping simulation: (a) radial force–diameter curves; (b) maximum principal stress–time curves; (c) comparison of kinetic to internal energy ratio trends with the threshold limit of 5% (red dashed line); (d) comparison of kinetic and internal energies in the TTI = 5.0E-06 s case.
Table 9.
Results of the calculation verification activity on target time increment applied to crimping simulation.
Fig 9.
Model input sensitivity analysis on stent geometry: (a) effects on the global QoI; (b) effects on the local QoI when strut thickness and width are varied.
Table 10.
Comparison of model input sensitivity analysis on stent geometry.
Fig 10.
Sensitivity analysis on Ni-Ti material parameters: (a) effects of each parameter on the radial force; (b) effects of each parameter on the maximum principal stress at a V-peak.
Table 11.
Results for model inputs sensitivity analysis on nickel-titanium material parameters: Values and errors reported for the radial force curve and the maximum principal stress at the maximum crimp configuration.
Fig 11.
Calculation verification on deployment simulation: effects on prediction of inner lumen diameter due to (a) mesh density, (b) element integration and (c) target time increment; (d) contact pressure generated in the vessel due to stent expansion.
Table 12.
Average inner diameter and diameter gain for different mesh density, element integration and target time increment.
The column highlighted is taken as reference for evaluating the difference.
Fig 12.
Validation of the deployment in the straight silicone mock vessel: (a) measurements of the outer diameter (OD); (b) qualitative comparison of the deployed configuration.
Table 13.
Results of validation with straight mock vessel in vitro comparator.
Fig 13.
Validation of stent deployment in the 3D-printed patient-specific vessels: comparison of the deployment for different stent diameter sizes in scenarios A and B.
Fig 14.
Results of in vitro (black) and in silico (red) quantitative indicators: outer diameter measured in proximal, central, and distal position for patient A (a) and B (b); minimal lumen area (c); incomplete stent apposition (d).
Table 14.
Measurement of the error among experimental and computational outcomes.
Fig 15.
Calculation verification applied to fatigue-life simulation accounting for the effects of mesh density, element integration and target time increment.
Table 15.
Results of the calculation verification activities applied to fatigue analysis.
The fatigue safety factor was normalized according to the reference case, here reported in the table with the symbol .