A Multi-layer Finite Element Model Based On Anisotropic Elastic Of Coronary Artery And Its Applicationcon

Cardiovascular disease is one of the major diseases which affects human health and survival, and cardiovascular disease usually occurs in the coronary artery. It has a significant meaning that proper understanding and awareness of the biomechanical properties of coronary artery for the prevention and treatment of cardiovascular diseases. In recent years, with the further studies of the biomechanical properties of arteries, many experts and scholars have presented a variety of constitutive hypothesis on the mechanical properties of the arterial wall. In 2000, a new anisotropic constitutive equation about the arterial wall is introduced by G.A.Holzapfel. This constitutive equation described a correlation between its internal structure and its macroscopic mechanical properties. It gave a strain energy density function based on variable. Holzapfel also researched the effects of fibers on the biomechanical properties of arterial wall. Then T.C.Gasser and R.W.Ogden further improved the constitutive equation respectively, and resulted in a more accurate constitutive equation. The simulation results obtained under the constitutive relation with the experimental results are very consistent, which validates the rationality of the constitutive equation.The main purpose of this study is to establish a true and reliable model of coronary blood vessel wall, which not only provide people a new approach to understand the human body biomechanical properties of soft tissue, but also give some help to study the treatment of cardiovascular interventional procedures such as coronary atherosclerosis, and Coronary in-stent restenosis. This paper researched the biomechanical properties of coronary artery wall by the assumption of the constitutive equation. In order to achieve this material constitutive relationship in finite element software, I conducted a secondary development of finite element software and coded user subroutines based on FORTRAN language, which finished its finite element simulation. Since single model of the arterial wall is not related to contact problems and the gemetery is simple, it uses a stand implicit algorithm. With the simplification of the shape of the arterial wall, we consider it as a cylinder wall. According to its symmetry, a finite element model of a quarter arterial wall was built and applied pre-tension and blood pressure to simulate the real dynamic environment. Uniaxial tensile test was simulated to impose the axial and circumferential tensile load with the arterial wall material parameters, and obtained its stress responses. Then the tensile test simulation experimented to the obtained three-dimensional model, and its parameters in different mechanical properties of materials were analyzed and compared with experimental results. The results show that the simulation results obtained with the experimental results were very close. Based on the above model, we have established the coupling structure model of a coronary atherosclerosis and coronary artery stent, and obtained a reliable simulation results.Arterial blood vessel wall model includes three parts, namely intima layer structure, the media structure and the adventure structure. In addition to the vessel wall itself, the coupled model of coronary stent and the arterial wall also contain plaque model and stent model. Holzapfel-Gasser-Ogden (HGO) and the Mooney-Rivlin material model material model were used to simulate the material behavior of artery walls respectively. The coronary stent is made of 316L medical stainless steel, which is a perfectly elastic-plastic material. Since the coupling structure involved in contact and non-linear large deformation problem, the dynamic explicit finite element algorithm is used to simulate the coronary stent and the contact deformation between the vessel walls, and we obtained stress and displacement distributions under different arterial wall models.