Dynamic effects on the formation and rupture of aneurysms.

Dynamic analysis of an axially stretched arterial wall with collagen fibers distributed in two preferred directions under a suddenly applied constant internal pressure along with the possibility of the formation and rupture of aneurysm are examined within the framework of nonlinear dynamics. A two layer tube model with the fiber-reinforced composite-based incompressible anisotropic hyper-elastic material is employed to model the mechanical behavior of the arterial wall. The maximum amplitudes and the phase diagrams are given by numerical computation of the differential relation. It is shown that the arterial wall undergoes nonlinear periodic oscillation and no aneurysms are formed under the normal condition. However, an aneurysm may be formed under such abnormal conditions as the stiffness of the fibers is deduced or the direction of the fibers is oriented towards the axial direction. Furthermore, the possibility for the rupture of aneurysm is discussed with the distribution of stresses.