Dynamic Mechanical Analysis Of The Bioprosthetic Heart Valve Based On ANSYS/LS-DYNA

From the point of Engineering mechanics, heart is the source power device of human blood circulation, and heart valves are the components to control blood flow one-way in the cardiac cycle. Once the heart valves disease or damage, it will threaten the lives and safety of patients. Present research shows, besides using drugs therapy for patients, the valve replacement surgery on patients with heart valve disease is an effective means to save their lives. There are two basic types of prosthetic valves: mechanical ones and bioprosthetic ones. Compared to the mechanical valves, bioprosthetic heart valves also have successful performance and there is no need for the patient to have immunosuppressive therapy, because of which the proportion of bioprosthetic heart valve used in applications increased year by year. However, their long-term performance has been disappointing. Most of the degeneration of bioprosthetic heart valves can be attributed to calcification and tearing of leaflets. The stress concentration is thought to be one of the main reasons responsible for the degeneration that makes bioprosthetic heart valves still have a large gap with human natural heart valves. Therefore, the evaluation of the bioprosthetic heart valve mechanical properties provides a reliable bioprosthetic heart valve mechanical analysis in the design and improvement of the bioprosthetic heart valve, so it has an important significance and value.Appling modern design theory and technology to the study of bioprosthetic heart valve design is an effective way to create the bioprosthetic heart valve with batter performance and batter durability. The geometrical parametric model of bioprosthetic heart valve was established by PRO/E based on the membrane theory and heart fluid mechanics. With the geometrical features of leaflets, the author use SHELL 163 element to analyze the stress distribution of a leaflet. This element is only used in explicit dynamic analyses. The meshes of the models are generated using the pre-processor of the ANSYS finite element package and translated into LS-DYNA using a conversion program written specially for the task.Stress analysis under dynamic load showed that the dynamic mechanical properties of ellipsoidal and spherical valve leaflets are superior to that of paraboloidal or cylindrical valves leaflets. The results showed that the maximal primary stress of the valve leaflets appeared near the stent which is the lacerated area of the valves leaflets. The thickness of valve leaflets also has a significant effect to the stress state of the valve leaflets. The dynamic mechanical properties of the valve leaflets with 0.5mm thick are superior to that with 0.4mm thick.The stress distribution of the bioprosthetic heart valve obtained though the analysis of finite element method for dynamic mechanical properties is much closer to the truth, and it is a useful attempt to the design of bioprosthetic heart valve. This provides important reference and basis for the design and optimize of bioprosthetic heart valve, and it has important guiding role and realistic significance in the research, processing and performance evaluation of the bioprosthetic heart valve.