A Two Dimensional Phenomenological Model for Damage of Arteries

Loss of mechanical strength of arteries can manifest itself in many ways including rupture of a vulnerable atherosclerotic plaques, burst of saccular aneurisms, rupture of artery/graft anastomosis, and traumatic rupture of aorta by impact loading due to automobile accidents. In all cases the fracture of the tissue leads to sudden cardiovascular events that often have a lethal end. To date there are insufficient experimental data on the mechanical strength of healthy and diseased vascular tissue. Most of the results refer to the failure properties from uniaxial quasi-static tensile tests on strips and rings. It was found that the tensile strength is different in the circumferential and longitudinal direction especially when it is determined from strain controlled dynamic tests [1]. Results form load-controlled fatigue tests have shown a gradual softening of the arterial tissue, development of a residual (plastic) deformation, and existence of S-N curve [2]. However, the information from uniaxial tests is not sufficient to predict the damage of tubular segments due to coupling between circumferential and longitudinal stress via constitutive equations and deformed geometry. Moreover, the mechanisms of arterial tissue failure remain unknown.