Structural analysis of percutaneous heart valves
- Figure 1: Deployment of a stent from a catheter tip; original form overlaid (transparent surface)
Within the heart valve prostheses project, FEA is used to set iteratively the geometry of a stent in which prosthetic leaflets are integrated. The simulation model allows the study of the stress-strain cases of the valves in a natural environment. Thus, physiological as well as "worst-case" scenarios are reproduced. These vulnerabilities, for example the basis of the physical material boundaries or the functionality of the model, are identified (see Figure 1). These weaknesses are optimized in design and hence achieve a stable and functional prototype.
Moreover, existing material models with experimentally determined material data are considered at the CVE. The correlation of simulation results and experimental data are investigated, in this case specifically for a nickel-titanium alloy (Nitinol), as shown in the stress-strain diagram of Figure 2. In the video, the simulation of a tensile test on a Nitinol Dogbone can be pursued.
- Figure 2: Simulation of a tensile tests with a stress-strain Diagram
Furthermore, the group is working on the implementation of the Nitinol material model in the Ansys Workbench (Contact: Y. Safi). The studies used in the field of percutaneous heart valves form the base of this investigation and gives the data for comparison. The future goal of this work is to be able to simulate the interactions between structure and flow, in particular regarding the operation of cardiac valves in the blood flow. This interaction is known in numerical analysis as a fluid structure interaction (FSI) and is the subject of current research.
- Figure 3: deflected spring
In the area of the artificial heart project, the energy dissipation of spring elements of the drive have been calculated (see Figure 3). These elements have to withstand a large number of vibration cycles without damage. In order to verify the durability of the spring, the tensions that occur at the maximum deflection are calculated and located. On the basis of those findings, the spring design can be optimized.
