Hgo model abaqus 6.13 free#
( 2008) compared three different methods in modelling stent expansion, i.e., no balloon (pressure applied on the stent inner surface), free rubber cylinder inside the stent and folded balloon. Cypher, Cordis) which are designed to be expanded by folded balloons. This is particularly the case for the recent generation of stents (e.g. ( 2008) assessed the importance of balloon folding in the expansion behaviour of a Cypher stent and proved that the folded balloon was the only model that produced results consistent with the data provided by the manufacturer, in terms of diameter change as a function of pressure. Modelling of a rubber balloon is relatively easy, and produces reliable results including both stent expansion and stresses in the stent-artery system (Chua et al., 2003 Ju et al., 2008 Schiavone et al., 2014). Rubber balloons, inflated by internal pressure, were generally used to simulate expansion of early generation stents (e.g. One factor that has important influence in the simulation of stent expansion is the type of balloon used in the modelling. The simulations provide essential information regarding the behaviour of stent expansion, recoiling, dogboning and residual stresses, which can be further utilised to guide stent design and surgery procedures (Chua et al., 2003 Lally et al., 2005 Pericevic et al., 2009 Zhao et al., 2012a Morlacchi et al., 2013). This surgery procedure has minimal invasive nature and provides fast and effective solutions to patients suffering from coronary stenosis, a major cause of heart attack.įinite element is an effective tool to simulate the process of stent expansion inside stenotic arteries, which helps to understand the insight of the biomechanical behaviour of the whole stent-artery system during the procedure. The scaffold is placed over the balloon and expands with the balloon when this is inflated by internal pressure. Stents are generally deployed inside the diseased artery by means of an angioplasty balloon (except for self-expandable stents). The composition of the plaque also has to be considered due to its major effect on stent deployment.Ĭoronary stents are essentially scaffolds, made of metallic alloys or biopolymers, used to sustain the blood vessels once expanded inside the obstructed arteries. The blood vessel should be modelled as a three-layer structure using a hyperelastic potential that considers both the first and second stretch invariants as well as the anisotropy. Conclusionsįolded balloon should be used in the simulation of stent deployment, with the artery partially constrained using spring elements with a proper stiffness constant. The stress distribution in the artery-plaque system is also different for different combinations of artery and plaque constitutive models. The use of anisotropic artery model reduces the system expansion at peak pressure when compared to the isotropic model, but with an increased final diameter due to reduced recoiling effect. The negligence of the second stretch invariant in the strain energy potential leads to the disappearance of saturation behaviour during stent expansion. Calcified plaque limits stent expansion considerably when compared to hypocellular plaque. Stress in the artery-plaque system has higher magnitude for stent expansion in a free artery due to more severe stretch. Fully constrained artery reduces the stent expansion when compared to free and partially constrained arteries, due to the increased recoiling effect. Resultsįolded balloon produces sustained stent expansion under a lower pressure when compared to rubber balloon, leading to increased stress level and enhanced final expansion for the system. Simulations were also carried out by considering free, partially and fully constrained arteries. Both folded and rubber balloons were considered and inflated with a linearly increasing pressure of 1.4 MPa. The arterial wall, consisting of intima, media and adventitia layers, and the stenotic plaque were described by different hyperelastic models. MethodsĬommercial finite element package ABAQUS was used to model the expansion of Xience stent inside a diseased artery with 40% stenosis. The choice of balloon type, system constraint and artery constitutive model plays an important role in finite element simulation of stent deployment. Finite element is an effective tool to simulate stent expansion inside stenotic arteries, which provides an insightful understanding of the biomechanical behaviour of the whole stent-artery system during the procedure.
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