基于有限元仿真的心脏瓣膜力学性能研究

发布时间：2018-05-03 09:32

本文选题：心脏瓣膜 + 脉动流检测　；参考：《沈阳工业大学》2017年硕士论文

【摘要】：心脏为人体循环系统提供源源不断的动力,心脏瓣膜作为阀门控制血液的单向流动。然而人的一生中瓣膜需要开合数十亿次,每个心动周期都要经历大变形过程,复杂的应力应变情况使瓣膜易发生钙化、撕裂等病变,从而影响整体循环系统的正常运转。为了更好地提高人工心脏瓣膜在体内的运行性能,瓣膜的体外性能测试是十分必要的。脉动流检测能够有效地模拟体内的循环环境,因而成为检测心脏瓣膜流体动力学性能的重要手段。本文以体外脉动流检测为基础,结合有限元分析方法有效地分析心脏瓣膜的结构力学性能、流体动力学功能间关系。本文研究脉动波在血液中的传播特性,理论推导心脏瓣膜在流体力作用下发生大变形情况时应力、变形关系式,并利用MATLAB绘制关系曲线。对心脏瓣膜流体动力学性能进行脉动流检测分析,研究心输出量、平均主动脉压力和心室驱动曲线对瓣膜性能的影响。为了深入分析心脏瓣膜在体内运行环境下微观受力情况,利用有限元技术研究瓣膜的力学性能。采用模态分析研究瓣膜结构的振动特性,谐响应分析不同频率的载荷作用下的动力响应;利用结构显示动力学模拟瓣膜运动过程大变形情况,基于任意拉格朗日-欧拉算法建立瓣膜和血液的流固耦合模型,分析瓣膜在血液循环系统下的运动情况,为后续人工瓣膜设计提供参数优化。结果表明,理论研究得出流体力作用下瓣膜表面中部受力最大,并以轴对称形式变化。生物瓣膜在体外脉动流检测下的各性能指标数值均符合ISO 5840国际检测标准,其中瓣膜的平均主动脉压力过大会增加血液泄漏百分比,心输出量过小会减小有效开口面积。有限元仿真结果显示,瓣膜收缩期应力集中在弯曲变形严重的腹部以及瓣叶缝合边;舒张期应力集中在瓣叶缝合边的两侧,仿真结果验证了理论计算的正确性。在脉动检测的不同时间点,瓣膜有限元模型与实验条件下的开口面积、流速近似相等,证明了有限元仿真的可靠性。
[Abstract]:The heart provides constant power to the human circulatory system. The heart valve acts as a valve to control the unidirectional flow of blood. However, the valve needs to be opened and closed billions of times in human life, each cardiac cycle has to undergo a large deformation process, complex stress-strain conditions make the valve prone to calcification, tear and other lesions, thus affecting the normal operation of the whole circulatory system. In order to improve the performance of prosthetic heart valve in vivo, it is necessary to test its performance in vitro. Pulsating flow detection can effectively simulate the circulation environment in the body, so it is an important means to detect the hydrodynamic performance of heart valve. Based on the detection of pulsating flow in vitro, the relationship between the structural mechanical properties and hydrodynamic functions of heart valves is analyzed effectively by using finite element method. In this paper, the propagation characteristics of pulsating wave in blood are studied. The formula of stress and deformation of heart valve under the action of fluid and force is deduced theoretically, and the relation curve is drawn by MATLAB. The effects of cardiac output, mean aortic pressure and ventricular drive curve on the valve performance were studied. In order to analyze the microcosmic stress of heart valve in vivo, the mechanical properties of valve were studied by finite element method. Modal analysis is used to study the vibration characteristics of the valve structure, and the harmonic response is used to analyze the dynamic response under the load of different frequencies, and the large deformation of the valve motion is simulated by the structure display. Based on any Lagrangian Euler algorithm, the fluid-solid coupling model of valve and blood is established, and the movement of valve under circulatory system is analyzed, which provides parameters optimization for the subsequent design of artificial valve. The results show that the central force on the surface of the valve is the largest and changes in the form of axisymmetric under the action of fluid force. The values of the biological valves under pulsating flow in vitro all accord with the ISO 5840 international standard. The mean aortic pressure of the valve increases the percentage of blood leakage and the cardiac output decreases the effective opening area. The finite element simulation results show that the stress during the valve contraction is concentrated on the abdomen with severe bending deformation and the edge of the flap is sutured, and the stress in the diastolic phase is concentrated on the two sides of the suture edge of the valve. The simulation results verify the correctness of the theoretical calculation. At different time points of pulsation detection, the opening area and velocity of the valve in the finite element model are approximately equal to those in the experimental condition, which proves the reliability of the finite element simulation.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R318.1

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