动脉粥样硬化的斑块破裂是中风和心肌梗死的主要原因.斑块破裂与血液和剪切应力存在一定的关系.基于血管是天然的周期性低应力环境,本文将血管斑块破裂处理成一个疲劳问题,将血管简化成圆筒,探讨斑块中的裂纹扩展与疲劳破坏,并考查血管内外径比、血栓、血压等因素对疲劳寿命的影响.应力强度因子的计算采用经典圆筒内壁单边裂纹的理论公式,疲劳裂纹扩展利用著名的Paris法则,并利用数值方法求解裂纹扩展过程.研究发现,在血管内外径比不变时,内径的大小对疲劳裂纹扩展的影响几乎可以忽略不计;血栓形成会增加血管壁厚,降低应力集中,该单一因素在疲劳意义上反而会有利;血压对血管疲劳寿命的影响非常大,成指数次减小或增加.

Plaque rupture is a major cause of heart attack. Mechanical factors including blood pressure and shear stress have been found to be related to the rupture risk. The blood vessel is naturally under a periodical and low-level pressure stress state, therefore, the plaque rupture can be treated as a fatigue problem. By simplifying the blood vessel as a cylinder, the crack propagation and the fatigue rupture are investigated. The theoretical solution for an edge crack in a classical cylinder is used to calculate the Stress Intensity Factor (SIF) with the Paris Law being utilized to determine the crack growth rate. The fatigue crack growth is numerically simulated. The various factors that may influence the fatigue life are studied. The results show that when the ratio of the external radius to the internal radius is fixed, the effect of the internal radius on the fatigue crack growth can be neglected; the thrombus with an increase of the wall thickness will reduce the stress concentration, this single factor may have a positive effect to the vascular life from the point view of fatigue; the blood pressure has a great effect on the fatigue life, in an exponential manner.