Influence Analysis Of Structural Parameters On Fatigue Performance Of Ventricular Septal Defect Occluder

In recent years,Ni-Ti alloy occluder has been widely applied in interventional treatment of ventricular septal defect(VSD),which accounts for about 25-30% of congenital heart disease.As one of the key performance indicators of the implantable device remained in the patient,the fatigue resistance of VSD occluder is gaining increasing attention in structural design.However,the current research and application of VSD occluder is mostly concentrated in clinical trials,while less in mechanical behavior based on finite element analysis.In order to improve the safety,reliability and durability of VSD occluder,this thesis conducted a preliminary study on its fatigue performance,providing technical reference for the structure optimization.And the research work is carried out on the following aspects:To begin with,in the discussion of constraint type as well as structural simplification,reasonable assumption and simplify means are proposed according to the work condition,structural form and material constitutive relation of VSD occluder.In view of the fatigue theory such as stress fatigue curve,the finite element modeling approach and fatigue analysis method of VSD occluder are provided,which are valid through the comparison between numerical simulation and test results.Then,the parametric analysis is conducted on the basis of symmetry WXVSDMD occluder,and the influence of parameters on structural mechanical properties is obtained,including curvature,height,size,cover shape,and wire diameter.The result indicates that,the critical position of fatigue failure is mainly distributed in the transition zone with large curvature between waist and cap.In addition,structure optimization suggestions are given that the VSD occluder possesses more flat capping,slender waist and thinner wire achieves superior fatigue performance.Finally,in terms of non-symmetrical WXVSDX and WXVSDP occluders,the finite element models are established for fatigue analysis,and the differences in fatigue properties of various sizes,wire diameters,as well as types were compared,also their related laws are summarized.Furthermore,researches show that,the fatigue performance improves with flatter bodily form and thicker wire,which has greater stress amplitude and shorter fatigue life.Moreover,under the same size,namely wire diameter,waist height,and waist diameter,the symmetric occluder has the lowest stress amplitude and longest fatigue life;and the WXVSDX occluder also satisfies the design fatigue life;however,the currently designed WXVSDP occluder fails to meet the fatigue performance criteria,which thereby needs further optimization in future.